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Old 03-11-2007, 11:45 PM   #19
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@ BailOut



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!
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Old 03-13-2007, 10:30 AM   #20
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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!
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Old 03-13-2007, 10:54 AM   #21
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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?


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Old 03-13-2007, 12:09 PM   #22
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@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.
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Old 03-13-2007, 12:38 PM   #23
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Quote:
Originally Posted by BailOut View Post
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!

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Old 03-20-2007, 02:17 PM   #24
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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!


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Old 03-20-2007, 05:16 PM   #25
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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.
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Old 03-20-2007, 05:21 PM   #26
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My last tank took me to 39.69 mpg.
Yeah but you said before that you don't rev over 3k... I DO!

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Old 03-20-2007, 06:13 PM   #27
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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.
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Old 03-21-2007, 06:45 AM   #28
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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.
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Old 03-21-2007, 12:51 PM   #29
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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.
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Old 03-21-2007, 02:23 PM   #30
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Yea but the problem w/ that is that the ECU never cuts the fuel to the engine, not entirely at least.
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Old 03-22-2007, 04:33 PM   #31
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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?
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Old 03-22-2007, 04:58 PM   #32
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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
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Old 03-22-2007, 10:38 PM   #33
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@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.
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Old 03-22-2007, 11:03 PM   #34
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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
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Old 03-23-2007, 09:00 PM   #35
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"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?
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Old 03-23-2007, 10:10 PM   #36
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Quote:
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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.
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