Using DFCO to increase your MPG [Archive] - Toyota Yaris Forums

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BailOut

03-10-2007, 07:21 PM

What is DFCO?

It is an abbreviation for "Deceleration Fuel Cutoff", and the Yaris' engine (1NZ-FE) has it.

How does it work?

When your Yaris is moving forward with zero throttle and is in gear (engine braking) the ECU (your car's computer) cuts off the fuel flow to the injectors. This means you are experiencing forward movement with no fuel cost.

Does this work on both the Liftback and the Sedan?

It is not dependent on body style.

Does this work on both the manual and automatic transmissions (MT and AT)?

Yes, but it is much more efficient with the MT. The MT can achieve DFCO in any gear as long as the clutch is engaged (meaning you don't have it pushed in) and your foot is not touching the throttle. Early versions of the AT (Including ones sold in the U.S. until around January 2007) can only achieve DFCO with a gear selection lower than (D)rive, i.e. 3 or L, but since half way through the 2007 model year the AT can achieve DFCO in all gears..

Is the Yaris the only car that does this?

Not by any means. Many cars manufactured since 1999, even a few as early as 1995, have this feature.

How can I tell if a vehicle other than the Yaris has DFCO?

Be careful with this test as you may lose Power Steering and Power Brakes during it! Choose the right time and location to perform the test.

On any level or slightly downhill road get up to at least 40 MPH, then start engine braking by keeping the vehicle in gear and letting all the way off the throttle while keeping the clutch disengaged (MT) or keeping the transmission in a gear lower than D (AT). Notice the deceleration force and the sound of the engine.

Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.

If nothing was any different with the ignition turned off then your vehicle uses DFCO. If it decelerated at a different rate or pitch with the ignition off then it does not use DFCO. Do not forget to start your engine back up!

How long does it take the Yaris' 1NZ-FE engine to enter and leave the DFCO mode?

The transition takes between 500 and 750 milliseconds (ms) depending on several other ECU measurements.

What will make the engine leave DFCO mode?

1) Touching the accelerator.
2) Dropping below 1,100 RPM.
3) Putting the transmission in neutral/disengaging the clutch.

Does changing gears make the engine leave and then quickly re-enter DFCO mode?

If you take <= 1 second to change gears (as most experienced drivers do) then no, you will remain in DFCO the entire time. However, if your shift takes longer than 1 second there is a chance you will leave DFCO for a few seconds.

Will the ScanGauge II show a DFCO state in the Yaris?

Yes, but it does it best if its firmware has been upgraded with the XGauge feature. Hit the "Menu" button, Select SETUP, then FUEL, then CUTOFF and set it to 21. Once done the instant MPG display will show 9999 MPG when DFCO is occurring.

If your SGII has not been upgraded with the XGauge feature you can verify a DFCO state by correlating several other readings:

1) LOD (Engine Load) will drop well below a reading at idle. My 5MT Yaris shows an LOD of 43 at idle but only 34 in DFCO.
2) GPH/LPH (fuel rate) will bottom out at 0.2 - 0.4 GPH or 0.75 - 1.5 LPH.
3) LP (fuel system loop) will be solidly Open.
4) MPG/LHK will go to the high side (it will take a few seconds but it will go quite high, i.e. 100+ MPG).

How can I use DFCO to increase my MPG?

Let me count the ways...

- When traveling down a grade get into DFCO mode instead of racing from corner to corner or riding your friction brakes, etc.

- As soon as you hit an exit ramp off of the highway go into DFCO all the way to the end of the ramp.

- When approaching a stop or turn use DFCO to decelerate down to just a few MPH before applying the friction brakes.

- When you're stuck in heavy traffic use the well-known technique of finding the right speed to keep a few car lengths of distance ahead of you and maintain forward momentum, then use DFCO to decelerate when needed instead of your friction brakes.

- Use DFCO to maintain controlled forward movement while you're trying to stay moving while approaching a traffic light that you're waiting to turn green.

How can I maximize my speed control when using DFCO?

By selecting the right gear for the purpose. Select a higher gear for faster DFCO movement and a lower gear for slower movement (this is where the MT really outshines the AT). Both transmission types can have their DFCO movement speed adjusted by tapping the fuel when a higher speed is required than gravity can achieve, and by light friction brake usage when some speed needs to be bled off but the next lower gear would be too much.

Does using DFCO hurt my vehicle?

No more than maintaining an idle, or maintaining a fuel-based engine load on it would be, as normally happens in these instances.

Is DFCO more efficient than using the clutch and/or friction brakes to stop?

When you push the clutch in or the AT enters its lowest power state your engine idles (the AT idles a bit higher than the MT in order to produce the pressures needed to operate the torque converter). Idling requires fuel while DFCO does not so DFCO is more efficient. However, you will not be able to use DFCO to completely stop all forward movement as you will eventually drop below 1,100 RPM, so the idea is to use DFCO as much as possible before engaging the friction brake system in the normal manner.

Is using DFCO like this legal?

Absolutely. Even those rare Interstate passes or other roads where engine braking is prohibited don't apply here because those areas have banned engine braking due to emissions controls (notice how semi trucks spew acrid black smoke when they are engine braking), but we are producing zero tailpipe emissions because we are not burning any fuel at all.

What kind of MPG increase will I see by using DFCO?

The answer will vary from person to person, vehicle to vehicle and according to driving conditions but you can rest assured that you will never see an increase in fuel consumption due to using DFCO. Remember that when in the DFCO mode you are using absolutely no fuel.

DFCO is also symbiotic with other high-mileage techniques. For example, ignoring tailgaters when you are doing the speed limit (or the safest speed for the scenario) applies to using DFCO on a downhill grade as much as it does when you're driving using the friction brakes (don't use fuel to speed up just to please a tailgater because they'll still be tailgating you anyway). Another example would be the one I gave above of using DFCO to control your momentum while waiting for a traffic light up ahead to change to green.

Here is one example of the mileage you can achieve in a Yaris without doing anything drastic:

As of this writing my 2007 Yaris Liftback is not quite 3 weeks old yet and will not even hit 1,000 miles until at least next weekend, so I am most definitely within the break-in period. Local temperatures have been 25-40F. My daily commute is over a mountain from 4,500ft. to 8,900ft. and then down to 6,300ft. over a total of 27.2 miles (one way), and I start that climb 1.3 miles after I leave my home. We are still on winter gas (which robs anywhere from 3-10% MPG) and I am running on Mud + Snow tires. In other words I am by no means in an optimal position to achieve high mileage.

My efficiency on that tank was 43.67 MPG.

Please feel free to post any questions or corrections you may have.

Nutzoids

03-10-2007, 11:24 PM

Wow... That's a lot to take in...

So your telling me, that since I have a 5spd Liftback... That if I simply take my foot off the Gas Pedal every so often...I will save gas?

:evil:

Black Yaris

03-10-2007, 11:28 PM

Hmm... good to know.... I think I am going to stop using Neutral so much then, my car sounds better slowing from 3rd anyway

eTiMaGo

03-10-2007, 11:59 PM

hmmm very informative.... Gonna have to experiment with that!

BailOut

03-11-2007, 12:29 AM

So your telling me, that since I have a 5spd Liftback... That if I simply take my foot off the Gas Pedal every so often...I will save gas?

:evil:

:laugh:

I'm telling you that if you take your foot off the gas pedal while your engine has forward rolling resistance that you'll save gas.

SailDesign

03-11-2007, 08:22 AM

Let me get this straight....
You're saying that if we drive normally (lifting foot off accelerator while we want to slow down) then we will save gas. How is that different from how we hve been doing it all along?
Or... are you about to tell us that the Yaris doesn't cut the fuel while we do this, but your $XX DFCO chipset will allow it to? This just HAS to be a sales gimmick, since the Yaris either has this feature or it doesn't. My money's on it NOT having it, so there is something to sell.
Of course, I'm quite prepared to be labelled an old cynic as well as an old phart, and have to apologise. I do that a lot :smile:
Steve

TrancosRt

03-11-2007, 08:55 AM

While it does sound like a prefab sales gimmick, if my reading skills don't fool me, it would seem this "DFCO" is a Yaris' ECU feature.
In any case, that;s kinda the way I drive (slowing down taking the foot off the gas, slowing down till I almost stall it, etc. The only difference is that I like to coast to stops in neutral when I see a red light kinda from far a away...)

eTiMaGo

03-11-2007, 09:15 AM

yes, that's what I understood too, a little-known feature of the car.
The idea makes sense, but it is confusing, I mean, if you're engine-braking, and the fuel is supposedly not being supplied, there should be no internal combustion, and hence, not much sound coming from the engine and exhaust, right?

zenodaddy

03-11-2007, 10:01 AM

I found a fairly detailed explanation here:

http://www.autoshop101.com/forms/h43.pdf

:eyebulge:

acrbill

03-11-2007, 10:01 AM

You ever hear a car that has an exhaust that pops and crackles when it is decelerating? That is because fuel is still being dumped during decel. When I got the Mopar stage 1 turbo upgrade for my PT one of the selling points was more fuel was being dumped to create louder pops and gurgles. LOL

Usually if you are coming to a stop light you will not have enough time to shed enough speed using this method.

If you are going down a grade I wouldn't recommend engine braking because of the obvious added wear to drive train components. Popping the car into neutral and riding the brakes will use very little fuel.

I have always been told that brakes are cheaper than clutches.

Also, large diesel trucks that use engine braking is a completely different setup than a gas car.

BailOut

03-11-2007, 11:50 AM

@SailDesign:

lol - This isn't a SaleDesign. Our Yarii (and many other cars on the road) already have this feature. I'm just trying to help folks understand how to maximize the advantage they can get from it simply by altering their driving style at a few key points.

@TrancosRt:

Try "coasting" in a high hear instead of neutral while approaching a light.

@eTiMaGo:

You still hear some engine sounds while in DFCO because your engine is not inactive but is acting as a compressor rather than a combustor. I doubt you would hear much at the tailpipe other than a soft whoosh of air, though, as air is still let into the cylinders to provide pressure (the resistance from compressing and ejecting air is what provides the engine braking in DFCO).

@acrbill:

The engine in the PT Cruiser does not use DFCO and the cracking and popping you hear on some turbo vehicles is a feature of the car's ECU that throws higher amounts of exhaust output through it when the car is at low RPM (i.e. idling in a corner) which keeps the turbo spun up at a higher RPM for its next use (i.e. shooting out of the corner). To maintain those pressures even with the turbo's waste gate open (which it has to do in order to dump excess energy) some combustion is purposefully taking place after the cylinders to create more pressure inside the early parts of the exhaust system. You can see and hear this in action on some rally cars.

If you spend some time on the technique of waiting for a light to turn green you'll soon learn to anticipate stops well ahead of time, mostly by looking further down the road than most folks do. Once you get to that point you will find that, more often than not and with the exception of some heavy traffic scenarios, you have more than enough room to maintain forward momentum before the light changes.

While the DFCO mode does produce engine wear so does idling, and since no combustion is taking place during DFCO there is that much less stress placed on the engine (again, in DFCO the engine is acting as a compressor rather than a combustor).

Using neutral and riding the brakes is specifically what you are *not* supposed to do on a grade as brakes experience fade or even failure (hence why there are "runaway vehicle ramps" on just about every long, steep grade in the U.S.). You should always use engine braking on a grade which will already put you into DFCO (as long as an AT is not left in overdrive)... I'm simply trying to show folks that they can maintain DFCO on grades for longer periods of time if they use gear selection and light, intermittent braking effectively.

While brakes are cheaper than clutches we're not adding any additional stress onto the clutch when striving for longer DFCO periods unless we are downshifting on a downhill grade to dump momentum. However, this is no harder on the clutch then coming into a new gear at high RPM during hard acceleration (which most folks are wont to do at least once per week). Remember that a clutch does not experience any stress when it is in its disengaged state.

You're right that large diesel trucks use engine braking in a different manner but it's a moot point to our discussion. The only reason I put that into my original post was to allay concerns some folks might have when they see a "No Engine Braking Allowed" sign.

ChinoCharles

03-11-2007, 11:59 AM

Does this come with that Ebay +20 HP speed module?

BailOut

03-11-2007, 12:08 PM

Does this come with that Ebay +20 HP speed module?

:laugh:

Only USD $1.99 + $19.99 shipping, and I promise it's not just a $0.50 1 ohm resistor! :clap:

Nutzoids

03-11-2007, 12:09 PM

BailOut… I believe you 100% that this DCFO thing is on our car… I am just a bit skeptical that it makes all that much of a difference...maybe for automatic cars it does, but there is a pretty steep grade near my house that I take almost everyday…and normally I just pop my car into Neutral and coast down it… It’s almost a full mile lone… and if I start the grade at 60mph I don’t need to use my breaks until I need to turn off…

On my next fill up, I will force the car into DCFO mode and see if it makes any difference in MPG…

Just for the record I have kept a running total of my MPG ever since I have bought the car… So rest assured it will be accurate!

Any hints or pointers for me?

:evil:

BailOut

03-11-2007, 12:21 PM

@Nutzoids:

Testing this out for a tank or two and getting a feel for it is all anyone should do, and having a grade like that to play with is nice. However, if it is the only place you induce DFCO at then you won't see that much of a difference in your overall MPG as it's just one mile long and you should be getting at least 300 miles per tank. As such please see where else on your daily commute you can employ DFCO - even if it's just for a few seconds each time - in order to get a more accurate picture of it.

As I mentioned in my original post MT owners actually have some advantages over AT users because we have 5 gears to use DFCO with while they have only 2. This usually lets us pick the perfect gear for the need.

I commend you for tracking your MPG from tank to tank because this is the only way you'll get a feel for how your vehicle is behaving over time. I do the same thing for all my vehicles.

I can't give you many pointers beyond what I put in the original post (although it's a lot of reading this concept isn't rocket science) except that if you normally transition that grade in neutral and you gain no speed then it has to be quite a light grade, so try DFCO on it at the highest gear possible so that you have the least amount of engine resistance.

SailDesign

03-11-2007, 04:51 PM

Bailout,
Well, i guess I have to 'fess up and apologise. But.... ya gotta admit that it came off as a sales gimmick. You join on the 9th, and on the 10th post this. No "Yaris has this" but a "you can test your car like this".

As I said - I am used to apologising.

BailOut

03-11-2007, 05:54 PM

Thank you for that, SailDesign, and I've made some small changes to the guide to make it more clear that the Yaris has this feature.

My original post certainly didn't sound like a sales pitch to me but you're not the only person that had an initially negative reaction, so that means that either I did indeed do a poor job with the presentation or you folks on this forum have been hit with some spam-type things here in the past and have become hyper vigilant about it. heh

By the way, joining on the 9th and posting this on the 10th happened because of two things. I didn't find yarisworld.com until someone on priuschat.com pointed it out, and the reason I was discussing my new Yaris on priuschat.com is because the first forum I found was yarischat.com which I chose to not work with as it is an abandoned site that's been overrun by spammers and scammers.

Once I figured out the DFCO thing I felt I just had to share, and eventually ended up here.

SailDesign

03-11-2007, 09:01 PM

Thank you for that, SailDesign, and I've made some small changes to the guide to make it more clear that the Yaris has this feature.

<snip-de-dip>

Once I figured out the DFCO thing I felt I just had to share, and eventually ended up here.

No worries - welcome aboard (says he, only being a member about 2 weeks longer than you...)

Ah Yum

03-11-2007, 11:45 PM

@ BailOut

:clap:

Like you, I try to maximize DFCO when coasting to stop and when timing the lights. It also gives grounds to the "Pulse and Glide" technique, which, although somewhat effective on a non-hybrid, I find too cumbersome.

Alternatively, when going down steep hills, I opt for engine-off coasting because the engine-braking during DFCO slows down the car too much and limits the gliding distance (note to others, when the engine's off, you still retain power-steering and -brakes [although limited] by putting the key in "Ignition II" position, the spot right before inflicting the Starter Motor. But I wouldn't recommend this to the most drivers.

When you receive your ScanGauge II, you can do us a huge favour to find the RPM where the 1NZ-FE comes out of DFCO. Thanks!

eTiMaGo

03-13-2007, 10:30 AM

Well I've done a bit of experimenting with this, mainly using the AFR meter.

When the car idles normally, either when sitting there, or when travelling, with the clutch pedal pressed, the AFR does its usual lean-rich-lean-rich dance.

So, let's say I am traveling at 60km/hr, and I soon need to slow down. If I just press the clutch, as mentioned above, the engine will idle. But, when I engage a lower gear then let go of the clutch, there is a quick rich burst, then the needle is pegged down as lean as it can show as long as I am riding the engine brake.

Of course, this is not proof that there is no fuel flow at all, but we can be quite sure there is a lot less fuel being used when engine braking then when idling.

Oh and BTW to the guy who said that down a hill, save your transmission and use the brakes, bad bad bad idea, I grew and learned about driving in mountainous/hilly places, that's the best way to get to the bottom of a mountain with useless red-hot glowing brakes and trying to slow yourself down by the power of prayer. The engine brake is in no way detrimental to your clutch (unless of course you feather the clutch all the time to control your speed), is completely safe for long descents, and as we now see, can save a lot of fuel!

Nutzoids

03-13-2007, 10:54 AM

Bailout,

I started my new tank of gas the other night and began trying this out... My first impressions...

I use 1st gear a lot less now... the fact that I stay in gear until I hit the light, or traffic makes it so I hardly stop moving... And to me that's nice...

I found over a half dozen places on my drive to work and home from work where I can just do it for 15-30 seconds without worrying about keeping up with traffic... so that too is kind of nice...

I do a have a question though... Does this DFCO shut off when I hit the breaks?

:evil:

BailOut

03-13-2007, 12:09 PM

@eTiMaGo:

Thanks for the information! My ScanGauge II hasn't arrived yet (I got in with the group buy on PriusChat so it should be here shortly) so I'm glad someone else is providing hard data.

@Nutzoids:

It sounds like you're making progress, and that's great. :) No, using the friction brakes will not disengage DFCO. The 3 ways you will leave DFCO are:

1) Touching the gas pedal.
2) I don't know the exact RPM yet but if you drop below about 6 MPH in any gear the ECU will start sending fuel.
3) Using the clutch on the MT or using overdrive on the AT.

For example, using just the brakes (no clutch) while engine braking will not affect DFCO at all, and this is how I dump extra speed on short, steeper sections of the downhill parts of my mountain commute.

Nutzoids

03-13-2007, 12:38 PM

The 3 ways you will leave DFCO are:

1) Touching the gas pedal.
2) I don't know the exact RPM yet but if you drop below about 6 MPH in any gear the ECU will start sending fuel.
3) Using the clutch on the MT or using overdrive on the AT.

For example, using just the brakes (no clutch) while engine braking will not affect DFCO at all, and this is how I dump extra speed on short, steeper sections of the downhill parts of my mountain commute.

Good to know!

:evil:

Nutzoids

03-20-2007, 02:17 PM

Yo BailOut,

So I did a full tank of gas using your DFCO method... and even though there was a big snow storm here are the results!

03/12/07 - 03/19/07

305 Miles on tank... 29.65MPG

Which is on the high side of my MPG, but nothing outstanding... My highest was 31 (Back when I was breaking in my car)

Like I had said earlier... it was more convenient, didn't have to stop at red lights and stop signs!

So yes I can see where it will help, but don’t expect too much… I will continue to do it until my next oil change… but this was the first tank!

:evil:

sqcomp

03-20-2007, 05:16 PM

I've been using the transmission to slow the vehicle for very long time. Works very well when you need to stop in an emergency. My last tank took me to 39.69 mpg. This is the first vehicle I've owned that has actually performed to it's advetised mileage rating.

Nutzoids

03-20-2007, 05:21 PM

My last tank took me to 39.69 mpg.

Yeah but you said before that you don't rev over 3k... I DO!

:evil:

BailOut

03-20-2007, 06:13 PM

I'm glad you saw your increase in MPG despite the adverse conditions, Nutzoids. Using DFCO seems to do more for me, but probably because I commute over a mountain 5 days a week and can always use it extensively on the downhill side.

DFCO took me from 36 MPG to nearly 43 MPG without trying very hard, and I'm now at 44.86 MPG by combining some other hypermiling techniques with DFCO.

pennystocks

03-21-2007, 06:45 AM

Yea i dunno bout this. When i had my yaris and dropped it down a couple of gears it actually used more fuel, 0.3-0.5 GPH (gallon per hour) Idling is 0.2 GPH. I'v never seen below 0.2 GPH ever.

It does reduce the fuel being sent to the engine for that RPM vs on the gas but it uses more gas than at idle. And engine braking wouldn't seem to increase fuel economy speaking that you want to keep as much momentum as possible (coasting) when slowing down.

BailOut

03-21-2007, 12:51 PM

We're not talking about moving around at differnet fuel-driven RPM levels, pennystocks. DFCO means your foot is entirely off of the accelerator, and using zero fuel.

pennystocks

03-21-2007, 02:23 PM

Yea but the problem w/ that is that the ECU never cuts the fuel to the engine, not entirely at least.

Lillydot

03-22-2007, 04:33 PM

so wait, how is this different from regular "coasting"? maybe i'm missing something 'cause i have always had an automatic car. lots of times i'll just take my foot off the gas and coast to a stop or down a hill, with this car and with others. is there a difference?

rstb88

03-22-2007, 04:58 PM

I have heard of this before but I never really used it in part of my hypermiling techniques. No tall hills to us it on. I'm glad to see that im not the only one thats keeping track of all their tanks. I think I might be missing one or two before I found gassavers, but now I'm hooked. Would you happen to know if my mothers 04Taurus would have it? Have you looked into cylinder deactivation, I've heard its hard to do it in a 4 cylinder, but I thought I'd ask. Oh and my mpg is with a heavy right foot, and I'm still over the epa rating*.

*using 2008 epa ratings opposed to the 2007

BailOut

03-22-2007, 10:38 PM

@Lillydot:

The difference is that you most likely drive around in "D" - overdrive - the entire time. When your AT is in that setting it will always drop into OD at about 2,000 RPM when you are "coasting" with your foot off the throttle. That's a fair amount of fuel it's using. In order to engage DFCO you'd need to be in gear 3 or lower.

@rstb88:

I doubt your Mother's 1994 Taurus has this feature as I don't think it was fuel injected, but carbureted. You can perform the simple test I outlined in my first post to be sure.

Yes, cylinder deactivation is very difficult to do with a any in-line engine, which 4-cylinders usually are, and basically requires an interchangeable cam system. The problem is that you need to be able to compensate for the disabled cylinder(s) by matching the timing between the remaining cylinders. With a V-type engine this isn't hard as you just turn off one of each "opposing" cylinder pair, but when it's an in-line system there is no "opposing" cylinder.

On a different note it is indeed a bigger benefit to use DFCO in a hilly or mountainous area but it is by no means relegated only to that geography. I also use DFCO at every stop light and stop sign, in traffic crawls, etc. With your tires pumped up (my RE92's are at 60 PSI) you'd be surprised how well you can maintain speed in a 5th gear DFCO segment.

eTiMaGo

03-22-2007, 11:03 PM

I've been doing a bit more experimenting with this, it's a bit hard to keep an eye on the road, the RPMs and the AFR needle at the same time, but it seems the fuel cuts back in once the revs drop below 900-1000RPMs, at least in 2nd and 3rd gear.

It's still hard to resist the subconscious impulse of pressing down the clutch when slowing down :tongue:

Lillydot

03-23-2007, 09:00 PM

"The difference is that you most likely drive around in "D" - overdrive - the entire time. When your AT is in that setting it will always drop into OD at about 2,000 RPM when you are "coasting" with your foot off the throttle. That's a fair amount of fuel it's using. In order to engage DFCO you'd need to be in gear 3 or lower".

so, i should shift to the third gear and then coast? is this safe to do in the middle of driving?

BailOut

03-23-2007, 10:10 PM

so, i should shift to the third gear and then coast? is this safe to do in the middle of driving?

That's correct, and it's perfectly safe as long as you're not going so fast that your engine will red-line when you go into 3rd. I'd say anything up to 55 MPH should be fine.

uncleyaris

03-23-2007, 11:03 PM

Does this come with that Ebay +20 HP speed module?

:laugh:

Basscat

03-24-2007, 11:10 PM

I'd have to say it works! Just keeping the technique in mind during my normal driving, on my most recent fillup I got 42.9 MPG, compared to a previous best of 41 and an average of about 38-39. Nothing scientific about my observations, but I'm convinced. I do live in hilly country, which probably makes more of a difference. Thanks for the tip!

hystria

03-25-2007, 11:10 AM

The only mod I have made to my Yaris so far ... I used 2.5oz. of Lucas Fuel Treatment at my second fueling.

My efficiency on that tank was 43.67 MPG.

I totally agree with the use of the DFCO, it also saves the brakes. whenever it's possible put the engine in compression, the car will also be more stable when braking.

About that Lucas treatement, not sure what it does, but one time a mechanic put a bottle of a strong injector cleaner into my civic gas tank, that increased dramatically the mileage, something like 25% more on the highway. now that it's good but it comes with a cost :smile:

BMGYaris

03-25-2007, 11:56 AM

SO WAIt? us AT should never switch it into third over about 55mph?

BailOut

03-26-2007, 08:26 PM

SO WAIt? us AT should never switch it into third over about 55mph?
We're not speaking about the passing gear you can invoke by pressing down a bit on the accelerator while in overdrive, but manually selecting "3" on the shift tree.

I'm not positive about 55 MPH as a hard limit but your owner's manual will have the definitive information. Also remember that we're speaking about dropping into "3" for a deceleration effect, meaning it will place a lot of load on the engine that wasn't there just a second before, wile accelerating past 55 MPH in "3" would have built RPM gradually.

This is why I say that 55 MPH is a good cut-off point.

daq421

03-29-2007, 02:40 PM

[

Does this work on both the manual and automatic transmissions (MT and AT)?

Yes, but it is much more efficient with the MT. The MT can achieve DFCO in any gear as long as the clutch is disengaged (meaning you don't have it pushed in) and your foot is not touching the throttle, while the AT can only achieve DFCO with a gear selection lower than D (overDrive), i.e. 3 or L.

Help me understand this.. I should begin using the 3 - L positions on my A/T Yaris to slow down? This is how to activate the DFCO?

-Peter

BailOut

03-29-2007, 04:02 PM

Help me understand this.. I should begin using the 3 - L positions on my A/T Yaris to slow down? This is how to activate the DFCO?

That's correct, whether slowing down for a stop or just trying to maintain a certain velocity (i.e. on a downhill run).

daq421

03-29-2007, 04:23 PM

That's correct, whether slowing down for a stop or just trying to maintain a certain velocity (i.e. on a downhill run).

Hrrm,

So shifting into 3rd (or lower) won't just create engine braking? Or at least just cause higher revs?

Ok I'll try it..
-Peter

BailOut

04-07-2007, 09:09 PM

The original post has been updated with solid timing data as well as info on DFCO with a ScanGauge II.

AustinYaris

04-07-2007, 09:15 PM

I still don't understand how this is more fuel efficient than just coasting in neutral.

churp

04-07-2007, 09:29 PM

AustinYaris

04-07-2007, 09:34 PM

If I understand it right....idling in neutral still has gas going to the engine (small amount but enough to keep it running), while this totally cuts gas off to the engine during this period (nada/none even while the engine is rotating).....correct???

I think that's the idea... but regardless... say you're coasting in neutral at 40mph down a gradual incline, you'll maintain that 40mph for much longer in neutral coasting than in 3rd gear. Right?

I would imagine that in 3rd gear... you would come to a slowdown much more quickly having to use more gas.

BailOut

04-07-2007, 09:43 PM

AustinYaris

04-07-2007, 09:54 PM

AustinYaris,

churp hit it dead on. As for costing in N vs. 3 I don't know if you have the AT or MT but with my 5MT I can maintain my speed in a 5th gear DFCO on as little as a 2% grade.

Part of taking advantage of DFCO is selecting the right gear for the scenario. As I've mentioned a few times before this is where the MT really outshines the AT but the AT is by no means unusable for this.

Ah... I see where I was confused... the 3rd gear thing really only applies to AT... I actually have a MT.... So you can use DFCO in the other gears... For some stupid reason, I thought DFCO would work only in 3rd gear regardless of MT or AT. :redface: Anyways.. I just got my Scangauge II today. I'll have to try out this DFCO. I'll post my results in a few days.

esquiva

04-08-2007, 10:02 AM

hmmmm...i've been doing this ever since...of course to save gas..i know im not using gas coz im not hitting the gas pedal..
....very good information

Lillydot

04-08-2007, 03:55 PM

something else i'm curious about when using this method: when is the best time to switch back to overdrive? do i switch back before i press my brakes? after i've some to a complete stop? before i press the accelerator again? does it even matter?

BailOut

04-08-2007, 07:11 PM

Lillydot,

Don't go back into OD until you reach a complete stop or are ready to accelerate again. That way you're sure to get the maximum benefit of a DFCO.

naossoan

04-12-2007, 02:00 AM

ok, I don't really understand how this would work.

How does it completely cut off fuel flow? Won't the engine stall? Or is that the point?

If you're coasting in 4th gear foot off the gas it shuts off the engine...but then when you touch the gas it starts the engine back up again?

How can the engine keep turning over when there is no fuel to ignite and push the cylindars back down?

I'm confused.

BailOut

04-12-2007, 02:15 AM

The engine keeps turning because the wheels are turning, which turn the axles, which turn the transmission, which turns the crankshaft, which makes the pistons move.

As stated in the original post the engine becomes a compressor rather than a combustor at this point. Think of it as the drive train operating in reverse... instead of the engine making the wheels turn the wheels are making the engine turn. Since your momentum and the wheels are doing all the work there's no need for the energy that fuel would provide, so the computer turns off the fuel injectors.

Yaris Revenge

04-13-2007, 08:28 AM

It's strange to think your engine basically shuts down every time you take your foot off the excelerator.... freaky!

~YR

ChinoCharles

04-13-2007, 08:30 AM

BailOut, can you feel this happen? For the last few weeks I have been playing with this and I think I can actually feel DFCO. In second gear especially, you'll feel the car kind of "smooth out" under decelleration. It almost feels like popping the clutch, only you're still in gear.

BailOut

04-13-2007, 10:05 AM

ChinoCharles,

You took the words right out of my mouth. :smile: 2nd gear is where I, too, can actually feel this at, both entering and leaving DFCO. It's very subtle (which is a testament to Toyota's engineering) but it's there.

If I let my RPMs drop below 1,100 in 5th gear (which never happens unless I do it on purpose) I can feel it when the fuel kicks back in because it's like a surge from an old, tired spring.

eTiMaGo

04-13-2007, 10:08 AM

Agreed, and it coincides with my AFR needle too, you can feel the tiniest of jerks a fraction of a second after you let your foot off the gas.

ChinoCharles

04-13-2007, 10:10 AM

Cool! I'm going to try and really pay attention my next fill up and see if I can't get my already improving mileage numbers even better.

nsmitchell

04-13-2007, 11:05 AM

I had a weird experience on my latest trips throught the hills of Virginia. I had my Rostra Cruise control going at 65MPH. Going down hills I felt the engine braking my speed so I maintained 65MPH even on a steep decline that you would normally speed up a lot on. (Coming down Afton Mountain in the Blue Ridge Mountains) I think this must have been DFCO, but I know my transmission stayed in 4th gear because I would have heard/felt my RPMs going up. Any thoughts? Could this be DFCO in action?
I tried finding infor on Rostra with no luck.

churp

04-13-2007, 12:47 PM

I've noticed around town strange (compared to other automatic cars anyway) almost like what I've been thinking downshifting while slowing down. Just never noticed a perceptable change in other cars while slowing down....does the computer possibly do this (downshift/DFCO on its own) without manually downshifting....or is it just my imagination?

BailOut

04-13-2007, 06:19 PM

nsmitchell and churp,

I can't answer your questions as I don't have an AT model to play with but it sounds to me like what you two have found is definitely possible.

AustinYaris

04-14-2007, 12:07 AM

BailOut,

I still can't figure this DFCO thing out.

Here's a real life example:

There is a steady downhill grade on the street of my house that stretches for about a mile. Once I get over a small hill, I can coast in neutral for the entire mile at 40mph dropping to about 20mph before I need to turn.
- ScanGuage reads 200-230mpg during the run.

If I am in any gear, even 5th gear, I can not make this run without hitting the gas. There is too much engine resistance. At about half way, the car slows down to 20mph, so I have to hit the gas.
- ScanGuage reads around 140mpg for the run until I hit the gas.

In this scenario, isn't just coasting in neutral better for FE?

BailOut

04-14-2007, 02:06 AM

AustinYaris,

Yes, in that case you're better off on neutral as you'll use less fuel idling the whole way down that grade than you would using DFCO for the first half and then using fuel for accelerating/maintaining the rest of it.

I cannot recommend the following to anyone not into hypermiling (this is my disclaimer so lay off the flames, please) but rather than just being in neutral for that span I'd be in neutral with the engine turned off and my ignition turned to the 2 position (Ignition II). This is called a Fas (Forced autostop) and the Yaris holds this posture very well as you still have PS (say thank you, drive-by-wire) and you also have PB for about 4 uses before you need to worry about anything.

The only drawback to Fas'ing is that the SG II turns off after 12 seconds. It doesn't really matter if you're already using DFCO, though, as the SG II doesn't read that properly and has already screwed up MPG and tank tracking.

AustinYaris

04-14-2007, 04:01 AM

Thanks for the clarification.

I actually just tried FAS for the first time 2 days ago, and was even able to reengage ICE by shifting into gear and releasing the clutch. A lot easier than I imagined.

I didn't mention FAS since it would obviously be more fuel efficient than DFCO. Secondary reason, was to avoid the flames. You're a brave man to mention it... lol.

Appreciate the note about SGII as well. That's what I figured, but wasn't absolutely sure.

Yaris

05-16-2007, 12:46 PM

With an automatic transmission, I find it more efficient to be in neutral when rolling down an incline, and then shifting to DFCO mode when I'm approaching an anticipated stop. I get the best mileage driving this way instead of always alternating between OD and DFCO. It doesn't make sense to accelerate with OD off when you can acceralate with OD on and then shift to neutral while cruising a fair distance before having to hit the gas pedal again.
I try not to accelerate at the exact moment I shift into drive because of the potential thumping of the transmission.
Does anyone know if shifting in and out of neutral while in motion is harmful to an automatic transmission?

drifto

05-16-2007, 09:00 PM

its a very simple system. during braking above 1100 rpm the injectors cut off. i feel this every time i come to a stop sign etc. your not going to feel the car hold back as if you are breaking, but you will see the rpm drop down slightly lower than if you had the clutch in. if you find that your idle is too low or unchanged the car may not be PDI'd correctly. on honda/acura the cars have to be roadtested a certain way prior to delivery for the idle to be correctly adjusted during fuel cut off. it doesnt work if your in stop and go traffic. its been around for a long time actually. it was designed to meet emissions standards back in the mid to late 90's. hope this helps..

Yarii

05-16-2007, 09:36 PM

I don't think it should hurt anything as long as you're not on the gas when you do it, and assuming you shift into the right setting (don't tell it to go from N into low at 60mph) but it'd be nice to get some more opinions...

With an automatic transmission, I find it more efficient to be in neutral when rolling down an incline, and then shifting to DFCO mode when I'm approaching an anticipated stop. I get the best mileage driving this way instead of always alternating between OD and DFCO. It doesn't make sense to accelerate with OD off when you can acceralate with OD on and then shift to neutral while cruising a fair distance before having to hit the gas pedal again.
I try not to accelerate at the exact moment I shift into drive because of the potential thumping of the transmission.
Does anyone know if shifting in and out of neutral while in motion is harmful to an automatic transmission?

churp

05-16-2007, 11:20 PM

I've been shifting my auto into neutral and coasting and don't see a problem...anything under 55 slides back into gear nicely without giving it gas.

Older cars I know had a problem when moving without the engine rotating, due to no oil pumping without the converter going. Without oil circulating in the tranny while moving---lots of problems. Think they have cured this since front wheel drive, but don't know for certain. If the owners manual says no towing of an automatic without a dolly or trailer, this is the reason. Just to be sure I won't FAS with my automatic.

edit: Shutting the engine down with standard tranny no problem if you're comfortable/brave.... I'll coast with engine running w/automatic though!

Yarii

05-17-2007, 12:15 AM

I think you're thinking of the automatics before (I think) like 1960... They used to have dual oil pumps, one off the engine side, and one off the driveshaft end... As transmissions became more reliable, the second pump wasn't needed, and it would in fact cause over pressure if you turned the engine off and costed downhill letting the rear pump build up pressure.... Lots of times it would blow tranny seals and spray the fluid onto the exhaust=big fire... On the plus side, you could push start those old automatics if you could get them moving fast enough since there was a pump that turned with the wheels (I've done it once on a buddy's vintage oldsmobile, pushing it with a pickup truck up to about 68kph before the torque converter had enough pressure on it to make the engine turn over) heh....

I've shifted in and out of neutral lots of times in my auto camry... Into neutral just isn't a problem ever - if you're coasting off the gas in OD, it basically puts itself into neutral anyway, but I've never tried putting it back into gear over 50kph just because I'm not sure how good that is for the system... When you think about it, I'd guess the stress of a shift from neutral into gear w/o touching the throttle isn't nearly as stressfull on the tranny as passing on the highway and having it kick down out of 4th into second with the throttle on the floor...

That said, in my old 88 crown victoria, I've done it lots of times, at highway speeds (100-120kph), and it never seemed to care. The electronics would think the throttle was wide open and to reset it (in order to slow down) you'd have to kill the motor and restart in neutral on the highway, and you didn't dare try pulling over to stop, or coasting to a slow speed... You try handling a 20yr old, 4000lbs car without power steering and a reserve canister so small you only get 1 shot of power assisted brakes... *looks for the smiley face of a car flying off the road into a tree*

Older cars I know had a problem when moving without the engine rotating, due to no oil pumping without the converter going.

churp

05-17-2007, 12:25 AM

[QUOTE=Yarii;86587]I think you're thinking of the automatics before (I think) like 1960... They used to have dual oil pumps, one off the engine side, and one off the driveshaft end...

I was thinking more of the ones that didn't have the rear pump.....they couldn't be started by pushing because no oil was circulating, and if you towed them even short distances you could burn the tranny out. Probably not a problem anymore, I just like to play it safe...cause if it is a problem, once you notice it, it's too late.

tim584

08-14-2007, 04:25 AM

Hi all
i want to know if the 2NZ FE engine is equiped with DFCO? (1.3 VVTi engine, like european yaris) :iono:
Thanks

BailOut

08-14-2007, 09:24 AM

tim584,

Please run the test outlined in the first post in this thread in order to determine if your vehicle has it or not. It should, but there's only one way to verify. :smile:

tim584

08-14-2007, 10:01 AM

Yes iknow that, but can i damage my engine when i do the test?

Pavel Olavich

08-14-2007, 02:39 PM

For auto transmissions, here is what you can do to get into DFCO mode:

When going down an incline, tap your brake lightly. This will cause the "grade logic" in the auto tranny to down shift a gear automatically, something that Honda pioneered years ago. Then you will find that the car experiences some resistence as you glide down the hill. The rpm's will increase, and if you have a scan gauge, the GPH value will often be 0.3 or 0.2. I suspect the car is in DFCO, as the MPG is 200+. I think the ScanGauge will never post less then 0.2 GPH, so even though your car is in DFCO, the GPH shows 0.2. I could be wrong on this, and also, the auto will not necessarily run the "Grade Logic" routine unless the conditions are ripe, in regard to incline, speed, acceleration, that sort of thing. I think that working with "grade logic" is better and safer then placing the auto in nuetral. I suspect long term tranny damage to do the nuetral thing. It is my guess that if the auto Yaris in fact has DFCO, then after it enters DFCO mode, it will pop back out at the point that the movement of the car no longer is able to pressure-turn the engine (via the transmission).

If DFCO works as I think it does, then it is far better then placing the auto in neutral, because keeping the car in D with grade logic auto downshifts will (1) maintain your speed, using the compression of the motor (2) allow you to drive your auto as intended, and probably eliminate damage from neutral coasting (3) DFCO mode turns off the injectors...while coasting in neutral does not, as the idle feed of gas is still maintained.

Oh before I forget, BailOut: Nice write up, but you have the "disengage" and "engage" terms mixed up....a manual transmission is engaged when the clutch pedel is out, and DIS-engaged when the clutch pedel is pushed in...but your point is not lost to us. ;-)

adamschneider

08-14-2007, 07:24 PM

joe keeney

08-14-2007, 07:42 PM

Its called hyper driveing.

Pavel Olavich

08-15-2007, 02:56 PM

I drove over the mountains twice last week and experimented with engine braking quite a bit on the downhills. (I have an automatic transmission.) I was experiencing the same thing that AustinYaris mentioned a few months back: with the exception of a few really steep hills, downshifting to 3rd slowed me down way too much, so I was having to put it in neutral to pick up speed again. As I understand it, DFCO doesn't kick in at all when you're in 4th ("D") in an AT, correct?

So, basically, when going down hills, I was in 3rd gear on the steep parts (which had the dual effects of activating DFCO and slowing down the car so as not to get out of control!), then I would bypass 4th and go into neutral for the shallower inclines. I didn't use D unless I needed to give it some gas. Does this sound like the best way to do it?

EDIT: I just saw Pavel Olavich's most recent post. Pavel, are you saying that the Yaris AT does go into DFCO mode even in 4th gear?

I believe that keeping the shifter in D can activate DFCO if you allow the tranny to automatically downshift, caused by the "grade logic" of the tranny....in this way, your shifter is in D, yet the tranny is in 3rd, and DFCO can happen, given the right circumstances of course. When I find myself driving down steep hills, I tap the brake a tad, and this often causes the tranny to automatically downshift, and I think when it does this DFCO is happening....but my car does not necessarily lose speed...it often just holds the speed constant, and this is often what one wants in these circumstances.

Pavel Olavich

08-15-2007, 02:59 PM

Honda uses the term "Grade Logic"....what does Toyota call their's? Anyone know?

adamschneider

08-17-2007, 12:32 PM

I believe that keeping the shifter in D can activate DFCO if you allow the tranny to automatically downshift, caused by the "grade logic" of the tranny....in this way, your shifter is in D, yet the tranny is in 3rd, and DFCO can happen, given the right circumstances of course. When I find myself driving down steep hills, I tap the brake a tad, and this often causes the tranny to automatically downshift, and I think when it does this DFCO is happening...
I just experienced this yesterday without even trying to: I was headed down off Mt. Hood, tapped the brake, and it definitely downshifted. The question now is whether this causes the fuel to be cut off.

By the way, how did people even learn about DFCO? A google search only turns up results on this forum, the cleanmpg.com forums, and a few others!

Pavel Olavich

08-17-2007, 12:39 PM

http://books.google.com/books?id=2MMAq5mIlE4C&pg=PA63&lpg=PA63&dq=decrease+fuel+cut+off&source=web&ots=cGtyfYYFl0&sig=oHRjguBZTMC1dbHb3SsYgZrhQQ4#PPP1,M1

BailOut

08-17-2007, 12:58 PM

By the way, how did people even learn about DFCO? A google search only turns up results on this forum, the cleanmpg.com forums, and a few others!

I can't claim credit for "discovering" DFCO as there are a lot of ECU/ECM programmers around the world that know about it even better than I do, but I never heard of it until I saw a post somewhere about someone rigging up a switch for their fuel injectors. I ran a search on something like "cutting fuel injector flow" and found the document that Pavel linked earlier: http://www.autoshop101.com/forms/h43.pdf

There's a section in that white paper titled "Deceleration Fuel Cut", and I latched onto it. I thought up a way to test for the presence of DFCO (covered in the first post of this thread) and confirmed it on the 2007 Yaris with the 1NZ-FE engine (I had quite the pucker factor on that first test... hehe).

Once I did that I posted it on CleanMPG and two of the folks there hooked up an indicator light on their fuel injectors (a 2002 Elantra and a 2004 Honda Civic) and verified that the injectors lost all power in a DFCO state. A 3rd person with an older vehicle (I can't remember what model, but it was a 1994) tried the same thing and found his injectors stayed on full-time.

I then spent some time figuring out how to trigger it and how to make it stop, and once all that was done I wrote it up here.

So, while I can't at all claim that I "discovered" DFCO I may be the first "Joe Six Pack" that tested it, confirmed it, found a way to turn it into a purposeful FE booster and then went public with it.

steved

08-17-2007, 02:17 PM

Maybe someone in this forum could hook up an indicator light on there Yaris to see if the injectors really do cut off. (especially an automatic)

This way there would be 100% proof that DFCO really works on our cars.

I would do it, but someone living in an mountain area would be better at testing this. ( and I'm useless in electronics and wiring)

ECHOKnight2000

08-17-2007, 03:36 PM

Honda uses the term "Grade Logic"....what does Toyota call their's? Anyone know?

I think Toyota referrs to it as uphill/down hill shift logic. For automatics at least. The engine won't gear hunt as much going down hill or up hill (granted if you're gradually going up a hill. I don't know if that has to do with what we're talking about but I bet it has some relation as far as DFCO.

I don't have a Yaris but the ECHO (auto) has a similar set up obviously not the up to date version like the Yaris. I have one question though. I have a scanguage II and I have one of the read outs on closed or open loop. The fuel loop or whatever...anyway I read that when the loop is open it actually means the ECU cuts off fuel to the engine to save gas...so like when I cruise from about 55 and up and just let the car go even in drive the loop opens for a bit until I get to a certain speed. It really opens up either when I floor it or downshift to a lower gear like coming off the highway. I was wonder if this is DFCO cause it cuts off fuel or at least I think it does. Can anyone help me on this who knows about cars? Thanks!

Pavel Olavich

08-17-2007, 04:42 PM

I think Toyota referrs to it as uphill/down hill shift logic. For automatics at least. The engine won't gear hunt as much going down hill or up hill (granted if you're gradually going up a hill. I don't know if that has to do with what we're talking about but I bet it has some relation as far as DFCO.

I don't have a Yaris but the ECHO (auto) has a similar set up obviously not the up to date version like the Yaris. I have one question though. I have a scanguage II and I have one of the read outs on closed or open loop. The fuel loop or whatever...anyway I read that when the loop is open it actually means the ECU cuts off fuel to the engine to save gas...so like when I cruise from about 55 and up and just let the car go even in drive the loop opens for a bit until I get to a certain speed. It really opens up either when I floor it or downshift to a lower gear like coming off the highway. I was wonder if this is DFCO cause it cuts off fuel or at least I think it does. Can anyone help me on this who knows about cars? Thanks!

I think DFCO and Grade-Logic are two completely different processes, and are not related, although this is not to say that they don't cooperate together.

As for open/closed loop, when open, the ECU uses "maps" for determining ignition, and other stuff. When the loop is closed, the ECU uses realtime calculations to control everything.....I could be wrong, so maybe someone has a much better explanation, as my sources are a bit flakey on this. I write this because I don't want to spread info if I'm not 100% sure about.

songa

12-03-2008, 05:11 PM

i know this is an old thread but still very important and relevant...and im also sorry for not having read the entire thread yet as i am in a bit of a hurry so im sure im missing some details but i have one quick question..

DFCO is great, but say you are coasting downhill and you want to pick up as much speed/momentum as possible so you can continue coasting once the road levels off a bit. if you stay in DFCO, you will feel that it is holding your car back a bit, aka "engine braking." this scenario is only good because the DFCO is cutting off fuel. However, because of the DFCO you are not taking full advantage of gravity from the downhill slope and are therefore losing out on some added speed/momentum that you would get if you were to coast in neutral instead. this is a trade off...an opportunity cost issue. does this make sense?

so to my logic, if you really need that extra speed and momentum that you would get from gravity going downhill, neutral coasting is more beneficial. you use minimal fuel for a much faster speed and larger momentum that you will benefit from once the road levels off. this way, you can take advantage of much longer distances for a lil bit of fuel.

if you dont need the extra speed and momentum, DFCO would be more fuel efficient because you are not using any fuel at all. however after the downhill, you may not be able to coast much longer as you have limited your speed to an extent. this means you can coast for a shorter distance than the neutral coasting method, but you will be doing it at no fuel cost at all.

does this make sense?

Sodium Duck

12-03-2008, 05:31 PM

DFCO is just ONE driving tool. Like all fuel saving tools and techniques, is to be used in certain situations -- not all. Your point has bassically already been discussed before.

To be a hypermiler, you use a combination of all different driving techniques and styles to attain a maximum MPG. Sometimes you use DFCO on one hill, and shift into neutral on another. Or whatever else it is that you do.

Bullet120

12-04-2008, 12:38 AM

voodoo22

12-04-2008, 06:59 AM

DFCO down hill, gain some speed, use no fuel at all.

Neutral down hill, with car on, gain a little more speed and burn fuel otherwise not burned.

Hmm, no fuel, or some fuel. Which sounds more efficient?

Not to mention neutral coasting and autos don't like each other. However, ICE off neutral coasting in a MT is very efficient.

Like Sodium Duck says, it's a combination of techniques based on your situation. In situations where you don't want to slow down, but the decline is not steep enough to allow you to use DFCO without losing speed. That's when you want to use N.

You are also wrong about coasting in N in an auto. Most newer autos have no problems and incur no damage from doing this. You don't need to rev match or anything.

It really doesn't matter how efficient a maneuver is with a MT when you're driving an AT. Most AT's cannot ICE off coast without incurring damage, but some can. For the masses who can't N-ICE on coasting is their best choice when DFCO isn't suitable.

Sodium Duck

12-04-2008, 07:03 AM

*thinking - thinking - thinking* Oh snap, you're wrong!

On initial thought, you're scenarios make sense. But -- you have to look at the big picture. As I said before, it depends on the situation which driving technique/tool you should use. There is no one perfect, end all - be all, thing to do to save gas. It is a mix of things that you do and when you do them. Now, you tell me which one of my scenarios is more efficient.

Going down a small hill, that levels out at the bottom for 400 yards, until you get to a stop sign.

You COULD use DFCO, use no gas at all on the small hill portion, then be forced to use gas at the bottom because you would have no momentum left.

OR

You COULD shift into neutral and simply coast to the stop sign - not touching the gas once.

OR

You COULD build up some speed on the other side of the hill, and turn your car completely off at the crest (granted you have a manual).

OR

You COULD do whatever to get down the hill, then use hang time to get to the stop sign.

OR

You COULD go crazy, remove your spare tire, rear seat, stereo, interior plastic, go on a diet and lose soem weight, etc. Drop a couple hundred pounds of weight from the vehicle and just drive over the hill normally.

I don't feel like digging out the numbers, because, as I said before, this has been discussed many, many times here before. DFCO is the most fuel efficient thing to do when you use it in conjunction with ALL driving techniques/tools. There are many things you can do to get better MPG, but DFCO is not always the best. You have to consider the bigger picture!

Sodium Duck

12-04-2008, 07:04 AM

Like Sodium Duck says, it's a combination of techniques based on your situation. In situations where you don't want to slow down, but the decline is not steep enough to allow you to use DFCO without losing speed. That's when you want to use N.

You are also wrong about coasting in N in an auto. Most newer autos have no problems and incur no damage from doing this. You don't need to rev match or anything.

It really doesn't matter how efficient a maneuver is with a MT when you're driving an AT. Most AT's cannot ICE off coast without incurring damage, but some can. For the masses who can't N-ICE on coasting is their best choice when DFCO isn't suitable.

*clapping* Thank you!

And umm, what's ICE stand for? All I can think of is "in car entertainment."

BailOut

12-04-2008, 10:10 AM

ICE = Internal Combustion Engine :smile:

songa

12-04-2008, 10:18 AM

silver_echo

03-08-2009, 07:10 PM

found out last night that my 01 echo does have DFCO! sweetness!

Slick

04-23-2009, 02:41 PM

Alright, I read all six pages and noone stated the answer to my soon to be question. It has been stated that the A/T will not enter DFCO in D. Then it was stated that it might inter DFCO in D, or at least enter "grade logic". It was discussed that shifting between N and D or 3 and D may or may not be harmful to an A/T.

Soooo, in order to get best results on a non-grade road, should I downshift 3,2,1 (in order to keep the RPMs up) in order to stay in DFCO while coming to a stop? If so, this isn't bad for the transmission? Or is it that as long as i'm not winding the tranny up to 4 or 5k on a downshift it will be fine?

Would ya'll recomend just shifting from D to 3 and just riding that for as long as possible?

Thanks in advance for any help or advice.

MadMax

04-23-2009, 04:22 PM

Maxh91

04-23-2009, 06:21 PM

Slick

I've been led to believe that the AT will cause the DFCO to kick it but not as quickly as a manual would. However, I downshift to '3' and even down to '2' to maximize the DFCO savings. It seems to help...and it should not cause any problems with the transmission as long as you aren't downshifting to '2' at 70 MPH...

Cheers! M2

I'm not an Transmission pro (AT) but how much high the RPM can be in 3th when downshift to 2? I only downshift at 1300 to be sure. I don't want to destroy my AT if i downshift to early! I don't really know how much the AT can rev safely when engine braking. :thumbdown:

MadMax

04-23-2009, 06:35 PM

I wouldn't pop down to '2' above 40 MPH, that's about my upper limit...your car will let you know if you downshift too early!

Cheers! M2

Slick

04-23-2009, 06:36 PM

It has been my experience that the best way to tell when to downshift an automatic (don't flame me hypermilers) is to accelerate slowly starting in 1 and listening to the engine. When its starts to whine medium-loud then you know you should move it into 2. Repeat all the way to drive. After this, you should be able to guesstimate when its safe to downshift. eg. Shift from D to 3 anywhere under 50. 3 to 2 anywhere under 25. 2 to 1 under 15. This example is probably not at accurate shifting speeds, its only an example.

Darb

05-08-2009, 11:06 AM

Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.

Whoa whoa, question. Doesn't the AT require you to be in park (P) in order to restart the engine? Or are you just shifting down to 3 and L? *confused*

BailOut

05-08-2009, 11:20 AM

Whoa whoa, question. Doesn't the AT require you to be in park (P) in order to restart the engine?
Hello Darb,

No, you can start it from N(eutral) as well. However, if you would like to do it from P(ark) you still have your power brakes after the engine is off for at least 4 touches.

Marthos

08-04-2009, 05:38 PM

Lets make this simple.

DFCO is for slowing and/or stopping the car,

If you need to stop at the bottom of a hill, or you want to go slower down a hill, DFCO is for you.

Start down the hill, Auto Trans people may need to tap breaks or even downshift into 3, Manual people just let off the fuel pedal.

The engine will start to try to slow the car, at this point your not using ANY GAS (DFCO).

When at or near the bottom apply brakes, when stopped put trans back into D (which is really OD). If you were just slowing the car some, just pop it back to D and hit the go pedal!

You saved gas.

If you were to bump the car into neutral, all the stopping would be on your brakes and the engine would Idle (use some gas) all the way down.

If you need to coast after the bottom of said hill, DFCO is not for you! Coasting on flat ground requires forward momentum, DFCO Scrubs forward Momentum.

If DFCO slows the car to much and you find yourself back on the Go Pedal before the bottom, you are not saving gas.

DFCO stops your fuel injectors from injecting fuel into the cylinders.

R2D2

08-04-2009, 09:57 PM

Yaris Hilton

08-04-2009, 10:42 PM

The AT downshifts to hold back the coasting car if you touch the brake. Touch the gas and it upshifts to coast freely.

Marthos

08-08-2009, 01:01 PM

Also, the tranny will not down shift till rpms are safe.

I have tried it on a 1/4 mile, big downhill grade leaving my home lots of times, with a stop sign at the bottom.

i pop it into 3rd going 40, and it downshifts right away and revs ups a tiny bit, when i pop it into 2nd it almost always downshifts right away (2nd goes past 50mph if ya floor it from a stop) rpms go up, sounds kinda cool, then when im at around 25 i pop it to 1st and have to hit the brakes for it to downshift. I think it shifts down when im around 18 to 20 mph.

I dont have a tach, but I am sure it never revs past 5k after it downshifts, I think there is some kinda over-rev saftey lock out possibly?

The whole process seems very nonharmful to me, and i know im saving a little gas and a lot of brakes.

Marthos

08-08-2009, 11:36 PM

Tested this today while cold light was on and when popping into first at 25 mph it went right to 1st gear, still dont think it reved much maybe 4k.

Edit = I guess i should mention, this is a steep hill, im on the brakes pretty good when I did shift it to 1st, revs droped fast, I have no tach and am guessing at the rpms.

Edit = Tried again cold light on, into 1st at 30 and it shifted right away, the trans acts totally different when the cold light is on, wonder if this means the shift points could be remapped?

Marthos

08-09-2009, 09:16 PM

Guess I can quit testing, found this in owners manual.

Pg 126 (c) using engine braking

"The transmision will downshift to second gear when the vehicle speed drops down to or lower than 53 mph."

First gear is 26 mph.

GMKing

08-31-2009, 04:54 PM

I just bought my toyota yaris this last friday and I love it, but one thing has been bothering me and I think it may be this DFCO

when I coast my vehicle (automatic, btw) without going into neutral it seems to "drag" kind of like engine braking, but when I coast it in nuetral there's no drag. I was wondering is this "drag" the DFCO? and if it saves on fuel then why does it cause the vehicle to slow down at a faster rate than in neutral?

Yaris Hilton

09-01-2009, 12:22 AM

Yes, it's the DFCO. Yes, it slows down the car faster than coasting in neutral, because the car's momentum is spinning the engine with no power being generated, just drag. It's not meant for increasing gas mileage, but for eliminating exhaust emissions while the car is coasting. If it's coasting down a steep enough hill to overcome the drag, you're saving gas over having the engine still running at idle power. If you're on level ground, you'll save gas whenever you're coasting toward a stop and would be using the brakes sooner without it. But it won't always save gas. Under conditions where it makes you slow more than you want to and you have to give it more gas to make it up, you may lose a bit.

GMKing

09-01-2009, 03:34 PM

exactly the issue i've been having. the fact that it slows down quicker as I'm trying to coast really aggravates me, screw emissions, I'm trying to get somewhere, guess I'm just gonna have to get into the habbit of putting in neutral

Yaris Hilton

09-01-2009, 05:21 PM

I've gotten used to the DFCO and pay little attention to it. But at the moment I'm travelling with the family in my old minivan that doesn't have DFCO, and it's startling how slowly it decelerates on flat ground with the engine idling! I have to use the brakes a lot more.

09Yarisguy

09-02-2009, 02:49 AM

I appreciate this thread and forum...I had no idea my new car had this system so I've been throwing it in idle on long downhills or rolling to a stop and being proud of the 38.5 MPG average I've gotten so far. I will try this with my next tank for comparison and let you know exactly what this does for me.

Just FYI though, there are a few places I'll still be coasting since there's a couple of half mile lengths on the highway where I can roll without losing any momentum. I figure I save a bit on gas for idling instead of gassing and I get a nearly free mile out of each trip to work.

BailOut

09-02-2009, 09:42 AM

It sounds like you're off to a great start, 09Yarisguy. :thumbsup:

127.0.0.1

10-20-2009, 09:56 AM

2010 yaris 5dr HB,

I find that scangauge cutoff set to 16 most accurately represents DFCO and 21 did not.

21 reported 9999 when I was not DFCO, merely foot off gas at 60mph which is not DFCO...there is still some fuel running to keep my decel rate from dropping too much. 16 now it never misreports.

I watched TPS. TPS lowest number is 15, but DFCO still will not always occur at TPS 15. But DFCO cannot occur anywhere
16 or above, so cutoff at 16 is perfect. when i drop to 15, scangauge reports some high mileage 180 or so, but won't
flash me the 9999 until I feel (with me arse dyno) the actual DFCO condition. so...I think...at least for my piglet, cutoff 16 is accurate.

Yaris Hilton

10-20-2009, 10:00 AM

Foot off gas at any speed with the torque converter locked up and engine spinning over about 1000 RPM puts mine into DFCO. I can feel the sudden small increase in drag after about 1/2 second.

jtcoop

10-22-2009, 08:59 PM

OK everybody I bought a Kiwi MPG and now I am having difficulty seeing or believing the DFCO theory. Traveling at say 40 mph going down hill, I let off the gas and the IMPG reads 165 MPG. If I push the clutch in the reading jumps to 180 or higher. The more speed I gain going down a hill with the clutch in the higher the IMPG reads. I have even tried tapping the brakes. Am I missing something? I will try and see what the LOD reading are tonight. I know at idle the LOD reads 16. I am not sure what it reads when I take my foot off the accelerator at 40 mph versus foot just touching the accelerator.
Regardless I am looking forward to my further education on the subject.

Yaris Hilton

10-22-2009, 11:50 PM

DFCO's not a theory. If your Scangauge isn't showing it, it's improperly set.

jtcoop

10-23-2009, 02:34 AM

For those who have a Scanguage, ( I do not ), when it is displaying Instant Gas Mileage, you take your foot off the accelerator, you get a large increase in the MPG being displayed. If you depress the clutch, do the numbers go up or down. With my experience it is going up. I, like most am trying to get the most bang for the buck. It makes sense to me that if the numbers go up with the clutch depressed, then I am getting more bang.
Yaris H, could something be wrong with the car? I am trying to find someone in my area that has a Scanguage to compare the IMPG.

Yaris Hilton

10-23-2009, 07:17 AM

I doubt anything's wrong with the car. DFCO's supposed to kick in after about 500-700 milliseconds. Are you waiting for it? You don't need a Scangauge to feel the sudden drag, it slows the car down.

127.0.0.1

10-23-2009, 08:55 AM

DFCO kicks in when

there is something in the transmisson keeping the engine spinning so the engine
doesn't actually stop turning

and when

the decel rate DFCO will make won't spill your coffee. it is programmed to kick in
but not make it buck. hence...in an automatic, it won't always kick in when foot
is off gas.

Yaris Hilton

10-23-2009, 10:25 AM

the decel rate DFCO will make won't spill your coffee. it is programmed to kick in
but not make it buck. hence...in an automatic, it won't always kick in when foot
is off gas.
It never makes it buck. But you can feel a small jerk when the fuel cuts out. It's definitely slowing down. The automatic usually has the torque converter locked when you're cruising around at light throttle, even poking around town at 25 MPH. Watch the tach. When the torque converter's unlocked, the engine speed will swing up and down with more or less pressure on the throttle. With it locked, the RPMs stay in strict lockstep with the speed on the speedometer.

Older automatic Yarises before mid-2007 model year may not have DFCO in Drive.

jtcoop

10-24-2009, 01:25 AM

When the RPMs reach 1100 and I actually feel the fuel cut back on, if I just let the car continue to coast. So I am pretty confident DFCO is working. I did notice today that the Load was reading 18 at one point on a long down hill run on the expressway. When I depress the clutch it went to 16. I thought I read somewhere in this post that Load had to be at 15 or 16 before DFCO would start. Right or wrong?
Everybody I again just want to say "Thank you" for your patience!

My bad....just reread very first post! Bail Out answered the Load question

Yaris Hilton

10-24-2009, 08:19 AM

Mine doesn't seem to kick in DFCO below about 1100 RPM, but also doesn't kick it back to idle power till it drops below about 800 RPM on the tach once DFCO's on. (I think at the same time it unlocks the torque converter.)

jjonrofl

12-16-2009, 03:12 PM

BailOut

12-16-2009, 03:19 PM

I've read most of these and think I finally know what it is- is it when I go down a steep hill going about 40-45, and when I touch the brakes, it buzzes and begins to brake steadily down the hill? If so, should I try to make this happen?
You don't have to touch the brakes to make it kick in. It will happen by itself shortly after you take your foot off of the gas pedal.

jjonrofl

01-01-2010, 03:21 PM

Brian- then what is the noise the engine/transmission/something makes when I begin to brake at about 45mph down a hill? And the car stays at about 40mph?

supmet

01-01-2010, 03:25 PM

Brian- then what is the noise the engine/transmission/something makes when I begin to brake at about 45mph down a hill? And the car stays at about 40mph?

DFCO doesn't make a noise, it just sounds like the engine revving from a downshift.

I'm not sure what the buzzing you are talking about is.

Yaris Hilton

01-01-2010, 04:56 PM

DFCO doesn't make a noise, and it doesn't rev the engine or downshift an automatic transmission. There's just a sudden slight deceleration as the idle fuel is cut off. You have to be paying close attention to feel it.

There is a separate function in the ECU that downshifts the transmission if you're coasting downhill and apply the brakes. It increases the "engine braking" so you don't have to use the brakes as much. Touch the gas pedal and let it off, and it'll upshift to high gear and let you pick up speed coasting.

jjonrofl

01-02-2010, 09:58 AM

Ah you're right, it must be the engine braking. is that bad for gas mileage? :wink:

jjonrofl

01-20-2010, 07:16 PM

Yaris Hilton

01-21-2010, 05:12 PM

Exactly. Lift your foot off of the gas.

127.0.0.1

01-21-2010, 05:19 PM

I still don't understand DFCO.. if it's seamless and you don't have to do anything, then how do you do what you said in the instructions?

"As soon as you hit an exit ramp off of the highway go into DFCO all the way to the end of the ramp." By doing what? Driving like you would normally?

yes it just means take foot off gas, so that

if the conditions are correct for DFCO, it will kick in.

it will not kick in if
you shift to neutral
or
have any gas pedal input

it really doesn't matter a ton for real world, single use... other than reduce emissions a little bit, and improve mileage a very little bit.

but over the life of the car x how many cars have DFCO, it matters a lot...the end user doesn't need to know
squat about it, it is computer controlled.

the end user can induce DFCO conditions more often than 'natural driving' would
by adjusting how they use the kinetic energy of the vehicle, and the gas pedal and gear choices.

why?

01-22-2010, 12:10 PM

it can improve gas mileage a lot if you plan to use it.

Yaris Hilton

01-22-2010, 02:52 PM

Keeping your foot off the gas usually does. :smile:

Falconia

02-25-2010, 08:48 AM

I just read ecomodder 100+ Tips for better fuel efficiency and I saw this:

Braking tips ...

44) The most efficient way to slow down

When you *have* to slow down, here's an approximate heirarchy of methods, from best to worst.

1) coasting in neutral, engine off (ie. roll to a stop);
2) coasting in neutral, engine idling;
3) regenerative coasting (hybrid vehicles)
4) regenerative braking (hybrid vehicles)
5) coasting in "deceleration fuel cut-off" mode (in gear, above a certain engine RPM)
6) conventional friction braking (non-hybrid or hybrid)

Choosing the right method depends on traffic conditions (following vehicles) and how quickly you need to stop.

REALLY?! Is it really more efficient to coast in neutral, with engine idling than using DFCO?! I thought DFCO cuts the fuel and it is better way to slow down...

BailOut

02-25-2010, 10:28 AM

REALLY?! Is it really more efficient to coast in neutral, with engine idling than using DFCO?! I thought DFCO cuts the fuel and it is better way to slow down...
Hello Falconia,

There are times and places for both techniques. If you only have a short distance to worry about, or you are going downhill, or you know you are likely going to stop then DFCO is best as it allows you to decelerate without fuel usage.

But if you would rather maintain more of your speed over a longer distance then coasting in neutral is better as it takes much less fuel to idle for a short while than it does to re-accelerate from a major momentum loss.

forgedinflame

03-03-2010, 01:09 AM

It's a good read, and I'll definitely pay more attention to how the car performs.

BTW, New guy here. Congrats on the sweet community you guys have made and I'm glad to add myself to it, I've already read tons of great tips.

pawsplus

03-05-2010, 02:43 PM

So . . . on the MT, avoid downshifting?

Loren

03-05-2010, 04:00 PM

So . . . on the MT, avoid downshifting?
Downshift when you need to when cruising or accelerating. (like if you don't have enough power to get up a hill in the gear you're in)

Delay downshifting on deceleration to prolong your DFCO coast. (downshifting earlier gives you more engine braking, which you don't want if you're trying to coast as long as possible "for free")

pawsplus

03-05-2010, 04:09 PM

Alrighty! Thanks!

Oh, and I'm assuming that my goal is to stay around 2000 rpms, right? I.e., upshift before it gets TOO far beyond that?

BailOut

03-05-2010, 04:44 PM

Alrighty! Thanks!

Oh, and I'm assuming that my goal is to stay around 2000 rpms, right? I.e., upshift before it gets TOO far beyond that?
High RPMs don't hurt much when you're in DFCO. I routinely go a little above 4k RPM while in DFCO in the mountains.

Loren

03-05-2010, 05:12 PM

Alrighty! Thanks!

Oh, and I'm assuming that my goal is to stay around 2000 rpms, right? I.e., upshift before it gets TOO far beyond that?

If you're upshifting, you're not in DFCO at all because you're accelerating. That's a topic for another thread. :wink:

If you're decelerating/coasting in DFCO, simply don't bother to downshift unless your revs get below 1500.

My typical DFCO maneuver is to just stay in 5th to about 2k or so (I don't really look at the tach), and then skip 4th and downshift to 3rd for the majority of a decel. If I can stretch it further (the light ahead of me is red, or traffic isn't moving), I might grab 2nd and try to maintain enough momentum to stay in 2nd and never have to stop or downshift to 1st if I can avoid it.

The short version of that is: Always coast for as long as possible in DFCO, and always try to time your position within traffic to maintain as much momentum as you can and avoid slowing/stopping unnecessarily.

sbergman27

03-08-2010, 10:31 PM

DFCO is not some exotic new feature. It's been a standard feature of most FI systems for at least 20 years. Many of the electronic feedback carbs of the 80s had it. What *has* changed is that its implementation has gotten more aggressive over the years. On my carbureted 1988 Chevy Sprint Metro, it doesn't kick in unless the engine is above 2500 rpm (about 56 mph in 5th) whereas, apparently, 1100 rpm is sufficient on the Yaris.

Also, it is not some magic feature that you can "use" to get better fuel economy. It does one simple thing: When conditions require *less* power than that produced by the 0.2 gal/hour that the Yaris engine consumes at idle, it eliminates that tiny bit of consumption. If that power is needed, e.g. to keep the engine idling, or even to maintain your desired speed when descending a hill, then the fuel is duly provided, and should not be considered to be any sort of waste.

talnlnky

03-09-2010, 11:49 AM

seemed pretty magic to me, i instantly saw a 10% (4mpg) increase in mpg's after I started using it.

sbergman27

03-09-2010, 10:56 PM

seemed pretty magic to me, i instantly saw a 10% (4mpg) increase in mpg's after I started using it.

You mean... after you started consciously aiming toward decelerating over a longer distance and using the brakes less?

Reality check: Consider that if you manage to stay in DFCO mode for a full hour, you've only saved about 0.2 gallons of fuel (specifically due to DFCO) since the Yaris' engine uses about 0.2 gal/hr at idle. To get a 10% improvement in fuel economy over the course of a tank of gas, you would have to spend over 5.5 extra *hours* in DFCO mode. Do you think that you are managing that much?

-Steve Bergman

BailOut

03-09-2010, 11:40 PM

You mean... after you started consciously aiming toward decelerating over a longer distance and using the brakes less?

Reality check: Consider that if you manage to stay in DFCO mode for a full hour, you've only saved about 0.2 gallons of fuel (specifically due to DFCO) since the Yaris' engine uses about 0.2 gal/hr at idle. To get a 10% improvement in fuel economy over the course of a tank of gas, you would have to spend over 5.5 *hours* in DFCO mode. Do you think that you are managing that much?

-Steve Bergman
You have quite the attitude about all of this, Steve. DFCO may have existed for a while but it is/was far from common knowledge. Just because you knew about it earlier doesn't turn the rest of us into bumbling idiots, or negate the uniqueness of me discovering and proving it on my own.

While what you say may be technically accurate you completely overlook the fact that fuel efficiency techniques bleed into and overlap each other. It is nigh impossible to extricate an intertwined technique from its siblings, so striving towards DFCO usage will invariably lead to more efficient usage of brakes and deceleration and downhill throttle control while simultaneously making the driver more FE-aware in general. If it is easier for folks to understand that whole set of skills simply as DFCO usage please let them be.

Please try to look beyond the trees so that you can see the forest. Getting caught up in the minutiae of an easy-to-understand and easy-to-use technique will do no one any good.

Loren

03-09-2010, 11:49 PM

Valid point, Steve. We're probably seeing most of our gains in MPG simply from changing our driving habits. DFCO is a good excuse to do it, but we wouldn't be using THAT much more fuel if the engine were idling at all times.

Let's say I was driving conservatively and went 400 miles on 10 gallons of gas. (a reasonable assumption for me, I usually do much better than that in city driving) My average speed for this tank of city driving is 30 mph, so total driving time is 13.3 hours.

Let's say that instead of clutching in and letting the engine idle, I spend 20% of my driving time coasting in DFCO. How much of a difference is it making? 13.3 hours x 20% = 2.66 hours at .2 gph... call it .5 gallons.

400 miles / 10 gallons = 40 mpg
400 miles / 9.5 gallons = 42.1 mpg

Wait... 42.1/40 = 5.2% improvement!

So, yeah... the bulk of our improvements (easily 10-20% over EPA without trying hard) come from driving style changes. But, I'd say that there's a solid 3-5% or more to be gained from making good use of the DFCO feature in city driving. And for people who practice the "pulse and glide" technique, DFCO can improve their highway mpg, too.

No, it's not magic. No, it's not "new" technology. But, now that people know about it, they have developed repeatable driving techniques to take advantage of it.

Footnote: Is it possible to spend 2.6 hours of a tank of gas in DFCO? I think so. Using myself again: My typical trip is maybe 20 miles round trip. If I don't hit at least 20 stops on that trip, I'm stunned. So, for each of those stops, I'm doing a full 20 seconds or so of DFCO coasting. Call it 7 minutes for every 20 miles. 20 of those trips on a 400 mile tank gives us 2:20 just from traffic lights. That's not including the amount of pulse & glide that I do. I'd say for any given mile that I spend cruising at speed, I'm DFCO coasting at least 10 seconds. (if my cruising speed is 45, that's 10 seconds out of every minute and a half, not at all unreasonable) This might only apply to half the miles traveled (the rest of the miles are spent accelerating or decelerating due to stops), so there's 200 miles x 10 seconds each for another 30 minutes of DFCO. I think my estimates here are very conservative for when I'm seriously "hypermiling", and they've added up to 2:50 of DFCO time.

While I completely get what you're saying, Steve... you can't deny that DFCO absolutely CAN make a difference in fuel economy for the driver to takes complete advantage of it.

And it all goes hand in hand. If you're maximizing your DFCO time, you ARE driving conservatively.

Loren

03-09-2010, 11:52 PM

Brian and I were typing at the same time... and said much the same thing in the end. Brian went on to say a few things that I was thinking, but didn't say because my post was too damned long already. Heh.

sbergman27

03-09-2010, 11:58 PM

You have quite the attitude about all of this, Steve.

I believe in accuracy, and in correcting misleading and/or erroneous information. What you discovered is that brakes turn kinetic energy into waste heat and that conserving kinetic energy helps fuel economy. DFCO is a relatively minor enhancement to that.

My clarifications in no way reduce the value of the information you have provided. But having a more accurate grounding in *why* it works will allow people to make more effective use of it.

That's not "attitude". It's a simple respect for truth. I believe in calling a spade a spade.

-Steve

sbergman27

03-10-2010, 12:12 AM

Footnote: Is it possible to spend 2.6 hours of a tank of gas in DFCO?
Actually, that's not the right question. You must spend that amount of *extra* time, over and above what would have been the case had you never even heard of DFCO, in order for the changed driving technique to result in that much improved fuel economy. And modern DFCO is designed so that people *don't* need to know about it to benefit from it. (I think the RPM cutoff on the Yaris is 1100 rpm?)

As mentioned in my previous post, this is about people having an accurate understanding of what is going on. And appealing to the fact that efficient driving practice involves a lot of interacting factors is really irrelevant to that point. Because the benefit specifically attributed to conscious use of DFCO *can* be separated out, and is relatively small in the grand scheme of things.

That doesn't make DFCO bad or insignificant. It just defines its place in the landscape better.

-Steve

talnlnky

03-10-2010, 11:48 AM

You mean... after you started consciously aiming toward decelerating over a longer distance and using the brakes less?

Reality check: Consider that if you manage to stay in DFCO mode for a full hour, you've only saved about 0.2 gallons of fuel (specifically due to DFCO) since the Yaris' engine uses about 0.2 gal/hr at idle. To get a 10% improvement in fuel economy over the course of a tank of gas, you would have to spend over 5.5 extra *hours* in DFCO mode. Do you think that you are managing that much?

-Steve Bergman

no... had nothing to do with being more conscious... It had to do with coasting in neutral, vs in DFCO... that instantly bumped me up from 36's to 40's. I was trying to get good mpg's from the first day i bought my yaris... took a few months before i found out about dfco. When you are going down a nearly 2mile long stretch of 5% grade highway at 60-65mph, your engine is using more gas than at idle.... I was able to change that 2 minutes of gas in my commute every day into zero gas usage. Then you add in all the coasts on highway exits that are a quarter mile long, then all the coasts to a stop sign/stop light...etc.

It's easy to rack up time in DFCO if you were making sure you were coasting in neutral before you heard of DFCO.... The last stick car I had owned was a 86Jeep Cherokee I had in HS. It didn't have DFCO... so I always popped it into neutral when coasting.

sbergman27

03-10-2010, 01:36 PM

It's easy to rack up time in DFCO if you were making sure you were coasting in neutral before you heard of DFCO....
Another way to put that is that it is easy to rack up more time in DFCO if you drive the car the way normal people do instead of trying to be clever with hypermiling tricks like coasting in neutral. These systems are designed with normal people in mind. Thus, there are sometimes FE advantages to being normal.

Regarding relative fuel use between normal idle and 65 mph in neutral, the Yaris uses about 20% less fuel in neutral. Normal idle uses 0.20 GPH, whereas coasting neutral uses 0.16 GPH.

So in 2 minutes of DFCO, you are saving a whopping 0.0053 gal (1/187th gal) of gasoline compared to coasting in neutral. Which is about 1/2100th of a tank. Keeping in mind, of course, that it takes longer to get down the hill with the transmission in gear due to that fact that the engine braking slows you down. So the actual savings would be less than that.

-Steve

BailOut

03-10-2010, 06:44 PM

talnlnky

03-10-2010, 07:00 PM

I see that you live in Oklahoma, Steve. Please try to expand your horizon enough to realize that not everyone lives in the Great Plain. Many of us, talnlnky included, live in hilly and/or mountainous regions, and in these areas it is not uncommon at all to be in DFCO for extended periods of time.

During my own commute there are instances where I am in fuel cut for as much as 7 miles at a time, for a total of around 20 miles per workday. Considering that commuting represents 90% of each tank, calculate that and then tell me that DFCO doesn't mean anything to FE.

Well, I used to live in a Hilly/mountainous area, now it's more of an extremely slow grade... but from time to time I get to go up and down some hills, or even the Cascade mountain range.

Some of my best tanks of gas have come from commutes that involved hills/mountains, where I was able to coast A LOT in gear.

Yoda

03-10-2010, 07:08 PM

so DFCO is better than coasting in neutral? cause i get 27 mpg right now lol

sbergman27

03-10-2010, 08:00 PM

I see that you live in Oklahoma, Steve. Please try to expand your horizon enough to realize that not everyone lives in the Great Plain.
Big mistake there, Bailout. My home address is in Oklahoma. But I drive to New Mexico, and/or Colorado nearly weekly. In fact, I just got back from Grand Teton National Park, in northwestern Wyoming, just south of Yellowstone, a few days ago.

(Yes, I drive *quite* a lot.)

Nice try. But you really need to get out more before you counsel me upon "expanding horizons". I probably cover more ground in a month or two than you do in a year. And more varied (and mountainous) ground, at that.

So why don't you try addressing the facts I've presented rather than trying to sneak in a personal attack based upon your guess about my driving experience. I have made quite a number of factual points, in previous posts, which you seem set upon ignoring.

Look. DFCO is a handy tool in the tool chest. But you have overemphasized it in comparison to some of the other useful tools there. I like seeing 9999 on my Scangauge II as much as anyone. But even over extended DFCO periods, the effect needs to be kept in perspective. Because the Yaris engine easily uses 20 times its idle consumption just as soon as you start ascending the next hill.

-Steve

sbergman27

03-10-2010, 08:17 PM

so DFCO is better than coasting in neutral? cause i get 27 mpg right now lol
Probably a little. You save about 0.00004 gallons for each second you do it. But you incur a fair amount of engine braking. And any fuel that did go through the engine if DFCO were not active would go to propelling the car forward.

So it really depends. Judiciously applied, it can help. But the ECU software is designed to do best when you don't try to second guess it.

BailOut

03-10-2010, 08:20 PM

So why don't you try addressing the facts I've presented
Because your "facts" change nothing. At the end of the day everything that you've presented is interesting but completely unnecessary, and contains as much opinion as fact.

I say again, getting caught up in the minutiae helps no one. Let us agree to disagree on the best implementation and/or public understanding of DFCO and move on.

sbergman27

03-10-2010, 08:53 PM

Because your "facts" change nothing.
Tell you what. Using 0.16 GPH for coasting in neutral, 0.20 GPH for idle, and 0.0 GPH for DFCO, and ignoring engine braking factors for now... why don't you work out for yourself how much DFCO could realistically be saving you on a per tank basis? I don't really care about the answer. But I think it would benefit you to go through the exercise.

Sorry if you feel I stepped on you toes regarding your "discovery". But the numbers I have presented cut to the very heart of this matter. If you disagree, then please present an alternative model.

why?

03-10-2010, 09:48 PM

wow dude you're just being a jerk. This is the real world, not some lab.

skoolafish

03-21-2010, 12:19 PM

awesome. i did not know this

STC

04-20-2010, 06:35 PM

I appreciate this Forum Thread. I’ve been using DFCO all the time since I read this thread. FE improvements have been incredible. Presently, I’m near making the 50 mpg range. This is a goal of mine to reach, before I use more advanced techniques.

I have a silly question? Does any one know?

There is a long mountain grade I drive every day. I let off the gas and use DFCO when I go down it. The long grade starts to level and my vehicle’s RPM drops down to around 1,000 – 1,100 RPM. But, then the grade steepens quickly causing my RPM to go back up to over 1,800. My MPH does drop down when I reach 1,100 RPM, but there are hardly any drivers, so I can do this...

Does DFCO kick back in automatically when the RPM goes back over 1,100? Or do you have to give it some gas (accelerator tap) over 1,100 RPM and then let the grade take over again? Is the Yaris ECU software designed to do this automatically? When the RPM gets just below 1,100 RPM and then climbs up again, I do nothing... just coast in the gear till I have to slow down and come to a stop at the bottom of the mountain.

Cheers...

micahsyl

06-29-2010, 08:28 AM

um,,, i think this is called "coasting" people have been doing it for decades lol i like the special name for it now... DFCO great marketing ploy!

BailOut

06-29-2010, 10:24 AM

um,,, i think this is called "coasting" people have been doing it for decades lol i like the special name for it now... DFCO great marketing ploy!
For decades, every time you took your foot off of the accelerator fuel still trickled into the carburetor or sprayed through the injectors at least at an idle-level flow. What has changed over the last decade is that carburetors have gone away and some car's computers are smart enough to turn off the injectors completely when you're in a "coasting" state.

That's DFCO - no fuel flowing at all when you coast in gear. In 65,000 miles I have never lost a fuel bar in the downhill segments of my commute (2,500 feet of elevation drop on the way to work and 4,500 feet of drop on the way home).

STC

06-29-2010, 11:04 AM

um,,, i think this is called "coasting" people have been doing it for decades lol i like the special name for it now... DFCO great marketing ploy!

Engine braking "coasting" (Deceleration Fuel Cutoff - DFCO) or neutral "coasting"? Two different coasting arenas. With the former you coast with the car in gear while the latter you manually throw the car into neutral and coast.

Today with engine braking coasting the ECU turns off the fuel injectors... the axles turn the tranny... the crankshaft turns ... the pistons then turn. Nothing new... most cars with a computer are capable of this.

:smile: Yes... neutral coasting has been done for many decades, since the advent of disc brakes some 40+ years ago. Could not do that with an old Model T...

Cheers!

advocate

07-07-2010, 12:13 AM

If the injectors are off then the car isn't burning any fuel, I get that.

But the car seems to still make a lot of noise. This is amplified by my tanabe exhaust I'm sure but my point is it sounds like the engine is still running even when coasting in what I believe to be DFCO.

'07 5 speed btw. Any ideas?

BailOut

07-07-2010, 02:58 AM

But the car seems to still make a lot of noise.
While no fuel is moving air certainly still is, meaning that in the DFCO state the engine is a compressor rather than a combustor.

advocate

07-07-2010, 03:30 AM

do the spark plugs still fire as well?

Yaris Hilton

07-07-2010, 09:16 AM

Yes.

KrazyDawg

07-12-2010, 01:40 PM

I've been doing the rollercoaster ride where you go slower up the hill and go faster down the hill while trying to maintain the same pressure on the gas pedal. Is it more fuel efficient to go down a steep grade using DFCO? This is where a ScanGauge would probably come in handy.

Yaris Hilton

07-12-2010, 02:11 PM

That's what the hypermilers call "Driving With Load." Yes, if you're going down a steep hill you'll back off of the gas and it will go into DFCO.

ChilliwackGuy

07-12-2010, 05:38 PM

I've been "coasting" or using "DFCO" techniques throughout my 13 years of driving - and mostly on 6 days a week commuting - 250KM daily totals!

The key for me has always been to minimize brake usage - and instead - focus on lifing and pressing my foot on the gas pedal. (I make it a game to coast to a red light!) Yeah - my passengers get annoyed but I have saved SO MUCH gas.

imjustagirl8_05

07-31-2010, 11:59 PM

So I just found this site and it's really cool. I am learning a lot about my Yaris! I bought my car in Jan 2007, I had no idea there were earlier models! I'm not sure if my car is 4 speed, but I think it is, since it's AT. Does this mean I have the DFCO? I haven't tested it out the way you described yet, but I definitely will! I just wanted to ask, is the ignition only to be turned off to test whether I have it? If I do have it, I would just have to lower a gear (like to 3) to get into DFCO mode, and it would stop using gas while slowing my car? Sorry, I'm slow, I had to read this post three times and search some terms to get it, but please let me know if I've understood correctly. Thanks!:help:

Maxh91

08-01-2010, 12:59 AM

Yaris Hilton

08-01-2010, 01:00 AM

Sometime in the mid-2007 model year they changed so the DFCO works in Drive. About the time yours was made, IIRC. The 2007 I originally bought for my wife has DFCO in Drive. No need to downshift. Don't switch off the key. While cruising along, let off the gas. .5-.7 second later, you'll feel a gentle deceleration as the fuel cuts off.

Maxh91

08-01-2010, 01:05 AM

I did not know about the mid-2007!

@imjustagirl8_05 I feel the DFCO after 1 or 2 second(AT). Just need to look at your RPM and you will see it slowing.

sickpuppy1

08-01-2010, 07:54 AM

I have a 2010 sedan w/AT and as much as I try to feel anything, I cant notice a thing when say I'm cruising to an exit ramp on the highway. I try to let off and notice DFCO but don't notice a thing. I'm curious, because if I keep it in gear, I can let off gas a little more than a quarter mile before the ramp and coast to the light at exit. If I just put it in neutral, I can coast at least a 1/2 mile or more and still have to use the brakes to stop. I never notice it kicking in and it seems I possibly would save more fuel by just coasting. Am I wrong here?

sickpuppy1

08-01-2010, 07:57 AM

That being said, I don't know why, but I always wonder if putting it in neutral and coasting is bad on the tranny, any thoughts, remember its an AT

Yarisduder

08-01-2010, 10:10 AM

I find you can tell if you have it just by watching the RPMs as the needle gets down to just above 1000 it will jump up a little before settling into an idle. If you don't have a Tach you can feel it quite distinctly if you brake lightly.

In my 2007 auto sedan, DFCO works in D but in the city it's mostly useless because of the low speed unless I put it into 3 just before braking, sometimes I'll drop into 2 also, but I find it more hassle than help. L is completely useless.

Maxh91

08-01-2010, 11:17 AM

That being said, I don't know why, but I always wonder if putting it in neutral and coasting is bad on the tranny, any thoughts, remember its an AT

It is not recomended that you put your transmission in neutral if your transmission is automatic. The transmission could overheat because there are no oil moving in the transmission if in neutral. Manual transmission dont have this problem.

If someone could confirm :biggrin:

sickpuppy1

08-01-2010, 11:33 AM

I know you shouldnt if the motor is not running and your coasting, but if memory serves me, the pump is running all the time, even in neutral.

daf62757

08-01-2010, 03:20 PM

It is not recomended that you put your transmission in neutral if your transmission is automatic. The transmission could overheat because there are no oil moving in the transmission if in neutral. Manual transmission dont have this problem.

If someone could confirm :biggrin:

I was always taught that moving the transmission from neutral to drive while moving could damage the transmission. The only place to move the tranny is from a dead stop.

Might be urban legend....might be for old trannys that were made by Govt. Motors back in the day....but my Dad taught me this and he was a Mechanical Engineer and I always thought his words were the rule!

So it is my rule!

Yaris Hilton

08-01-2010, 05:16 PM

BailOut

08-01-2010, 09:10 PM

DFCO is not worth giving all the attention people are giving it here. It's just cutting off the tiny bit of idle fuel that cars used to waste while coasting in gear. It's done for emissions control primarily. Nearly every car has it now. No biggie.
Actually, only around 50% of all cars have it now, and when employed willingly it is a valuable fuel saving tool. I'm surprised to hear you make such a flippant remark regarding something that so easily saves fuel.

Please also remember that for folks that live in hilly areas DFCO is even more useful. For example, when coming down the mountain I can stay in DFCO for several miles at a time. That makes a huge impact over the course of each tank.

KrazyDawg

08-02-2010, 11:46 AM

Actually, only around 50% of all cars have it now, and when employed willingly it is a valuable fuel saving tool. I'm surprised to hear you make such a flippant remark regarding something that so easily saves fuel.

Please also remember that for folks that live in hilly areas DFCO is even more useful. For example, when coming down the mountain I can stay in DFCO for several miles at a time. That makes a huge impact over the course of each tank.
That's a good point. I've seen my average MPG increase when using DFCO downhill.

Beer Jammer

08-03-2010, 10:17 AM

Hi All.

I've been insterestedin DFCO for a while now since Top Gear did a feature on it.
I have adjusted my driving style to encourage the DFCO, but my motives were not to see my MPG improve dramatically and save cash. My view is, if I have a leaky tap, (or fawcet to you guys over the pond :-)), that drips every 20 seconds, it wont add much to my water bill, but why waste the water?

Anyway, I have often wondered if the DFCO can be better used. I have an armchair thoery on utilising it, see what you think. Here is the theory:

Drive at 60mph, let the car engine break down to 50mph in DFCO, gently accellerate back to 60mph. Repeat the cycle.

Now, assuming that the decelleration and accelleration times were equal and on a flat road, would you see an overal improvement in economy, a reduction or no change?

KrazyDawg

08-03-2010, 11:25 AM

Yarisduder

08-03-2010, 08:31 PM

imjustagirl8_05

08-11-2010, 09:56 PM

I don't have an RPM gauge.. at what speeds will it be wise to use DFCO? I have been using it, but I'm not sure if it's pointless after I've already slowed.. what speeds are typically above 1100 rpm?

Yarisduder

08-11-2010, 10:25 PM

nmgolfer

08-11-2010, 10:51 PM

In "D" the engine kicks in as high as 30mph, in "3" about 20-25 and in "2" I'm not sure, but it's pretty slow. You can usually feel the engine turn on because all of a sudden you need to apply a little more brake, the car seems to surge.

I love that there's no answer to the laws of conservation of energy, I guess I'll have to raise this little flag here... :bs:

Assuming all else is equal (average speed etc) I agree with you re. COE however I'm open the possibility that while accelerating the engine is operating at a slightly better average BSFE than when running at the equivalent constant speed. Seems unlikely though and the net benefit needs to be quantified in controlled MPG testing rather than just anecdotal or scanguage feedback before I consider switching off the cruise.

rene0023

08-19-2010, 11:49 AM

Man information is great!

KrazyDawg

08-19-2010, 12:03 PM

Don't you just use the energy you saved "gliding" when "pulsing?" This pulse and glide thing sounds like it defies the laws of conservation of energy, same goes with the mountain driving. Please explain how this is possible.
When gliding you have an infinite MPG and even though your MPG will drop when slowly accelerating, the average MPG will increase overall compared to driving at a constant speed.

Resources:

http://www.metrompg.com/posts/pulse-and-glide.htm
http://www.greenhybrid.com/discuss/f22/physics-pulse-glide-3700/

brg88tx

08-26-2010, 12:00 PM

i have a early 2007 automatic yaris sedan, manufactured in june 2006. can anyone explain what this means, i copied it from the first page of this thread:

"Early versions pf the AT (Including ones sold in the U.S. until around January 2007) can only achieve DFCO with a gear selection lower than (D)rive, i.e. 3 or L, but since half way through the 2007 model year the AT can achieve DFCO in all gears.."

does this mean when i drive around in D that i am never in dfco mode, or does it mean that the dfco only kicks in as the vehicle slows down coasting in a lower gear than D (even though my shifter is still in D)? thanks

BailOut

08-26-2010, 02:13 PM

Hi brg88tx,

Perform the test outlined in the first post to see if yours kicks in DFCO in Drive or if you have to downshift:

How can I tell if a vehicle other than the Yaris has DFCO?

Be careful with this test as you may lose Power Steering and Power Brakes during it! Choose the right time and location to perform the test.

On any level or slightly downhill road get up to at least 40 MPH, then start engine braking by keeping the vehicle in gear and letting all the way off the throttle while keeping the clutch disengaged (MT) or keeping the transmission in a gear lower than D (AT). Notice the deceleration force and the sound of the engine.

Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.

If nothing was any different with the ignition turned off then your vehicle uses DFCO. If it decelerated at a different rate or pitch with the ignition off then it does not use DFCO. Do not forget to start your engine back up!

Yaris Hilton

08-26-2010, 04:15 PM

As I understand it, it means that DFCO never works when the shifter's in D. But testing it is the only way to be sure for yours. Individual cars often don't match the published specs exactly.

acutorque

03-26-2011, 05:19 PM

why set cutoff at 21, versus any other figure

flg

11-09-2011, 12:57 PM

Personally, I'm noticing that it works below 1100rpm unless I'm over 75mph. it dosen't work at all over 75mph? What is this over 75mph sh$%t getting stuck on 125-135mpg down a hill???
:frown:

jongscx

12-13-2011, 07:02 PM

I had always been curious about this. I bought a 2nd hand (AT) 2 DR hatchback, and didn't really know much about the Yaris.
By nature, I'd always coast as much as possible instead of the vroom-skrrrt everyone else did and noticed the engine sounded much different when I did.

I presumed it was engine braking or something. Good to know I'm saving gas.

charles nelson

01-16-2012, 02:33 PM

When I bought my '08 3-door...I noticed a considerable engine braking when I took my foot off the accelerator! When going to work I have to descend down a long steep hill. My Jeep Liberty always required considerable braking to keep it down to the speed limit. With the Yaris, being much lighter and DFCO, the vehicle will coast down at about the speed limit without any braking required.
I could literally feel the engine compression helping to keep the speed down.
Felt like a miniature Jack-Brake was on.
I once had a Mazda compact pickup...coming down through the mountains one time...I thought that I would have to replace the brakes by the time I had gotten down (even in low gear). The Yaris just stays at about 30-40 mph.

Edwin5000

01-22-2012, 11:45 AM

I don't have a Yaris (yet) , sorry. But DFCO can be a useful tool if/when you use it for slowing down or controlling speed on steep hills. For gliding, not so good. In my automatic Civic , it works in any gear , and at any RPM above 1000. For those who are not sure if they are in DFCO mode, you can usually feel the deceleration, or if you can't, your SG2 will show 9999 MPG (or 0.0 l/100km). You guys have ScanGauges , right ?

But I'm pretty sure that any "hypermiler" from CleanMPG doesn't try to glide in DFCO.

Edwin5000

01-22-2012, 12:04 PM

"the end user can induce DFCO conditions more often than 'natural driving' would
by adjusting how they use the kinetic energy of the vehicle, and the gas pedal and gear choices"

My keyboard is acting up ; I can't seem to make it highlight the text I want to present as a quote. This guy (127.0.0.1) seems to know a thing or two. Or at least I do not disagree with his post , lol. Does anyone know why he was banned ?
For my driving (not many steep hills) I find that invoking DFCO is most useful for driving with load (DWL) in traffic. When you maintain the proper interval , DFCO can mean you don't need to touch the brake when the person in front of you hits his. Any sudden lift of your right foot should put you in DFCO.
My findings/comments are based on my experience with my Civic automatic , which apparently works a little differently than the Yaris with regards to DFCO.

vincentg

04-11-2012, 09:09 AM

is there a video of how exactly one can accomplish this? :)

Amdkt7

05-16-2013, 02:53 PM

is there a video of how exactly one can accomplish this? :)

very simply, when you take your foot off the gas it happens, except as you slow down and the engine RPM's drop below around 1100 rmp the ECU starts supplying fuel again, to avoid stalling the engine.

Automatics do it too, but not as quickly, depending on the gear engaged.

Downshifting to slow the car when braking of course is the same thing, foot is off the gas. If the DFCO did not happen you would not get much engine braking.

It's really very simple, and you don't need to know anything about it for it to work. Knowing that it is cutting off the fuel will help you to decide to either coast with the clutch in or or out, depending on how much engine braking you need.

tooter

05-16-2013, 09:41 PM

http://troll.me/images/marty/marty-i-think-we-are-back-to-the-old-thread.jpg (http://www.google.com/url?sa=i&rct=j&q=old+thread&source=images&cd=&cad=rja&docid=Yq8TFlCSlnq2UM&tbnid=B1OWuUCOQjySWM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.troll.me%2F2011%2F06%2F10%2Fm arty%2Fmarty-i-think-we-are-back-to-the-old-thread%2F&ei=j4qVUfDoI-m0iQLoy4GoBA&bvm=bv.46471029,d.cGE&psig=AFQjCNHIJFVIj4csglhwIHY8GhP3XwWwJA&ust=1368841223223039)

:wink:

cali yaris

05-17-2013, 11:09 AM

you don't need to know anything about it for it to work

LOL

07liftback

07-24-2013, 07:35 PM

Haha this old thread was stickied so I assume it doesn't matter as much when people revive it.

Anyways, I've noticed the DFCO on the Yaris is not very noticeable on a manual transmission. With DFCO, my Yaris doesn't lug as bad as my civic did and I'm able to coast more effectively. Still getting 37-40mpg while hitting up to 85mph on the freeway and maintaining at least 70mph. Still rather impressive compared to my old civic which did around 30-33mpg.

Hayabusaboy

11-03-2013, 05:28 PM

When I brake going down a hill near my home the car feels like it downshift, it slows the car down so much that I have to accelerate to get the car to shift back to OD. I hate it, make me so mad some times that I floor board it to get going again. Is there a way to avoid this idiotic function?

nookandcrannycar

11-03-2013, 11:27 PM

Amdkt7

11-04-2013, 10:54 AM

Since you don't have a manual tranny, try sticking it in neutral so that it will roll free, if you want to coast. However, if you are braking you want the engine holdback.

If you needed to brake just a little bit, then want to coast again a small tap of the gas should tell the transmission to up shift again. Flooring it will make it want to downshift even more.

Automatics are really Nannytrannies.. they try to decide for you what you need. Manuals are for those who want to be in control!

nobodywise

09-15-2014, 09:58 PM

Is this avaliable for the 2nz-fe?

I love the back of my car, the front... not so much

Redflow2014

10-04-2014, 03:52 AM

Does the 2002 d4d have this?

Sent from my iPhone 5 using Tapatalk.

albee213

10-08-2014, 05:33 AM

It doesn't wear out your clutch to coast down hill in gear.

Brunno One

10-25-2016, 11:20 PM

I read about this DFCO thing and give it a try. 2013 Yaris Sport with manual transmission.
Got to say that I filled my tank with premium quality fuel, I over-filled it to the point of some fuel spill. I drive in the conservative zone of 40 mph to 60 mph.

Set the controls to monitor MPGs... When I lift the foot off the throttle that MPG monitor is set to 9999... I hit the throttle pedal and the MPG numbers started to flicker and constantly change. Low numbers if I press it to hard, good high numbers if I keep it in a sweet-spot of 45 mph / 55 mph.

Used the A/C just a few times minimum.

I am impressed that I was able to get over 80 driven miles on the over-filled fuel before the fuel gauge needle sets at the FULL mark and began to monitor fuel consumption.

So far I got 262 driven miles with half tank (drove a bit harsh on the weekend) and I think I can get 400 driven mikes when it goes to E (empty)

Average MPG monitor got better ratings too, from a 24.7 mpg to 38.5 mpg.

sunsanvil

08-29-2018, 06:38 AM

Is it possible that on newer models DFCO functions in 4th for the Autos?

Our 2018 will report a fuel flow of, literally, 0.0 when going downhill in top gear (not 3rd) with no foot on either pedal. The slightest press of the gas brings flow to a couple L/100 of course. Conversely with a gentle press of the break we initially still see 0.0, but as as the speed (or more likely the RPM) dips, a minimal flow is manifest at a certain point.

Seems consistent with how DFCO works, no?

kevinj93

08-30-2018, 04:15 AM

Yes, it definitely functions in 4th gear for the auto transmission.

As long as engine revs are above the minimum for the function, DFCO will operate in any gear. A couple of my regular drives each week involve hilly stretches of 70 and 80 km/h road which I usually drive on cruise control. It's easy to see the consumption drop to 0 L/100 km on the downhill sections. The transmission also changes down to third on some of these to provide more engine braking, so you don't have tomride the brakes as much.