DFCO and Autos

[MadMax]

OK, this may have been discussed in the numerous other threads on DFCO and fuel economy; but I was hoping I could get some clarification on how to get DFCO to work with an auto.

In an earlier thread on DFCO, it was believed that you had to tap the brake lightly to get the auto to downshift and engage the DFCO. Is this still the case, or can you simply let off the gas and let it kick in? Or, do you have to manually downshift into 3rd gear to get it to work?

Right now I am "only" getting 35 MPG, but I do have bigger, wider tires (215/45ZR17 Riken Raptor ZRs) which will drop the fuel efficiency a bit; but I drive it very conservatively and mostly at highway speeds, so I was hoping for a little better (and yes, I do adjust my computations for the larger tires). I am hoping that I could utilize the DFCO capability better to improve my mileage.

Cheers! M2

[MadMax]

Voodoo

I do add 7% for the added dimension of the larger tire (I had an earlier thread and someone provided a web site that gave me that number), and that is calculated into my figures.

It would seem logical that the DCO would kick in when you let off the gas, but I was wondering if anyone has ever tested it with a ScanGauge II on an auto...

Cheers! M2

[PreciousPups4U]

I have an auto and a scangauge. Like voodoo said it kicks in automatically when you take your foot off the gas. DFCO is just a fancy name for coasting seems to me. Course you get the most benefit when going down hill so as not to lose too much speed, but it works when approaching traffic lights and stop signs as well.

I am only averaging 34 mpg by the way with the stock 15" alloys that came with the car. Not much highway driving for me though. Pretty much all city or at least traffic area.

[MadMax]

PP4U

Thanks, that's the kind of info I was looking for!

Since I also have a Jeep Wrangler with an auto, so I am always trying to wrangle (pun intended) better mileage out of it. I get 15-16 MPG, another reason I wanted a Yaris to offset it!

Cheers! M2

[drummerboy2004]

DFCO occurs in the auto whenever you are above 1100 RPMs with your foot off of the gas. I have a scanguage, and watch it happen every time. I am not sure about 1st gear though... I never see it happen when I am driving in my neighborhood less than 15 mph. It will read around 50 mpg when I am below 15 foot off the pedal. Hope this helps...
Any other questions feel free to ask.

Matt

[drummerboy2004]

Originally Posted by voodoo22

Thanks for the feedback about pedal off and slow moving scanguage numbers. I was wondering it foot off the gas and slowly rolling in parking lots and towards stop signs was worth it.

I usually FAS to lights and home, but only do it below 30 mph and less than 100 feet. I have not had any problems, and am sure none will appear. If nothing else, yes, letting off the gas is what I do if I have to slow to light where I will not be stopped for more then 15 seconds (light about to turn green). It is a heck of a lot better than idling because my numbers went from 35 in the city to 45 most days.

Matt

[drummerboy2004]

Originally Posted by voodoo22

That's an amazing example about how much of a difference effort can make. Way to go.

I've started FASing to my parking space since I start work before nearly everyone. It's kind of fun when you screw it up a little and end up just crawling into your spot.

I have had to push my car into the spot like three times... I WILL NOT turn the car back on ... The thing that gets me is the wind, so beware. Oh, and I also try to keep my speeds between 30-40 (19tps)... but not 18 because unless you are on a downgrade you will slow quick. Hope that helps too...

Matt

[GeneW]

Originally Posted by drummerboy2004

I usually FAS to lights and home, but only do it below 30 mph and less than 100 feet. I have not had any problems, and am sure none will appear.
Matt

If some one else doesn't say it I will - do not FAS with an AT. The AT relies upon a pump to maintain internal lubrication, and that pump needs a turning engine. Shut off the engine and you're basically exchanging gasoline savings for transmission repair money.

Gene

[drummerboy2004]

Originally Posted by GeneW

If some one else doesn't say it I will - do not FAS with an AT. The AT relies upon a pump to maintain internal lubrication, and that pump needs a turning engine. Shut off the engine and you're basically exchanging gasoline savings for transmission repair money.

Gene

Thanks for the heads-up Gene... I have the lifetime powertrain on mine (perk from Toyota when I bought it), but still has a 100 deductible after the original warranty... I guess I will have to rethink my game plan. Doesn't NICE-on coasting essentially do the same thing? I have found mixed answers on the subject.

Thanks,

Matt

[drummerboy2004]

Originally Posted by voodoo22

Hehe, yeah, I almost didn't make it to my spot today because of all the rain water in the parking lot. Thanks for sharing.

No prob bob, and thanks for all of the info... Keep on FASing... well partially

Matt

[MadMax]

OK, I'm a noob...what is FAS and NICE-ON coasting?

Cheers! M2

[Revsson]

I had to look them up myself.
Another explaination is at their glossary page:

http://www.cleanmpg.com/forums/glossary.php

FAS = Forced Autostop
ICE = Internal Combustion Engine
NICE-on coasting = Coasting with the car in neutral while ICE running

Whew....learn something new everyday.....hmmm didn't my parent's tell me that?

[drummerboy2004]

Originally Posted by voodoo22

CleanMPG is a great resource full of an extremely mature group of helpful people.

Visit that place enough and you'll be surprised what rubs off on you.

He's right...

This is where this magician got all of his tricks

Even better than going to the site... try to find videos of Wayne talking hypermiling with reporters... It is 90% acronyms.

Matt

[yarswiss]

To answer the OP, DFCO can be engaged whenever the RPS are sufficiently high, the ratios of which (according to my Scangauge estimates) are 2nd:1700rpm, 3rd:1800rpm, 4th and Overdrive: 1800rpm. As a general rule of thumb, though, DFCO will engage whenever the rpms are significantly high and your car uses engine braking to slow down. For example, I live on top of a steep hill, so whenever I driver down in the morning, I go into 2 and the rpms will be around 2400, and DFCO will kick on, even though I'm only in 2nd gear.

Sometimes when I'm cruising about town, my DFCO will not engage, so I find giving a quick, light tap on the gas and then taking my foot off again will "force" the car into DFCO. This works best when you are on a long, smooth downhill where momentum keeps you between 30-40mph.

At freeway speeds, if you drive a hilly commute with steep enough downslopes that won't slow you down too much with engine braking, use DFCO whenever you go downhill. DFCO is also great to use whenever taking an exit, slowing to a traffic light on a slope, stopping at a stop sign, and coasting down any steep slope.

[GeneW]

Originally Posted by voodoo22

Nice on coasting causes no damage at any speeds in our cars.

My Scanguage indicated that NICE uses more fuel than DFCO. I agree with you that keeping the motor on keeps the pump turning but I didn't see any advantage to doing coasting while the motor is running.

Originally Posted by voodoo22

Some cars require you to rev match when shifting back to D, but as long as you shift back into D before you are going back up a hill(You don't need to, but it works better), the Yaris transmission will smoothly choose the correct gear. The Yaris manual states that our AT is flat towable for short distances at low speeds on flat surfaces. FASing to your parking space will cause no damage either, but FASing at hwy speeds or for long distances will cause you future transmission issues.

The manual says it pretty explicitly - "No Dinghy towing". I am not sure what "short distances" mean, but as best as I can recall the manual suggests using the rear wheels to tow or use a flat bed. I suspect that towing on the front wheels is used because the car must be removed rather than as a preferred towing option. Especially if the car was struck in the rear and cannot be towed any other way.

Not to be a smart ass, but you can also run your motor without oil for brief periods of time too. There is enough residual lubricants to keep things good for seconds worth of total operation, at least until one of the cylinders seizes or one of the bearings seize. An AT is a bit different in that it doesn't have as much heat generation as an internal combustion engine.

The AT uses the fluid for several purposes - lubricant, to operate the torque converter and to remove heat. Don't run that pump and you're letting the parts conduction cool. You will accelerate wear doing this.

I do not recommend FAS for any AT. I think the trade off of lowered reliability isn't worth the marginal fuel savings.

Best way to save fuel is to drive at "optimal" highway speeds, avoid heavy acceleration, reduce vehicle weight and keep the car in good working condition. Pulse and glide is also a good idea. I think many of the advanced techniques are almost in the domain of "diminishing returns", good when gasoline is horribly expensive or scarce but otherwise not terribly practical (though they are fun to do, as a challenge).

I live in a state where FAS is illegal. I drive at times of the day when the bars close and the drunks and hooligans are out and about. A car the size of a Yaris survives because of its maneuverability and agility. You cannot maneuver or be very agile in FAS.

I treat my Yaris as a motorcycle with a sheet metal skin, as I did with my CRX. So I don't use techniques that reduce maneuverability or require vigilance that takes away from my primary need of avoiding collision or losing control of the car. So even if I could FAS I would not do so on the road.

Gene

[GeneW]

Originally Posted by yarswiss

To answer the OP, DFCO can be engaged whenever the RPS are sufficiently high, the ratios of which (according to my Scangauge estimates) are 2nd:1700rpm, 3rd:1800rpm, 4th and Overdrive: 1800rpm. As a general rule of thumb, though, DFCO will engage whenever the rpms are significantly high and your car uses engine braking to slow down. For example, I live on top of a steep hill, so whenever I driver down in the morning, I go into 2 and the rpms will be around 2400, and DFCO will kick on, even though I'm only in 2nd gear.]

Laptops are getting cheap again.... I've so much wanted to plug one in and do a formal DFCO run. These aren't bad estimates though I think a laptop with logger software would do a better job.

Originally Posted by yarswiss

At freeway speeds, if you drive a hilly commute with steep enough downslopes that won't slow you down too much with engine braking, use DFCO whenever you go downhill. DFCO is also great to use whenever taking an exit, slowing to a traffic light on a slope, stopping at a stop sign, and coasting down any steep slope.

I tend to use DFCO this way too. I treat it as a "jake brake", which is used by truckers to reduce speed without consuming brake lining.

Gene

[drummerboy2004]

Gene,

Thanks for all of the insight. Oh, and I use NICE-ON coasting if I am going downhill or need to coast longer than the DFCO will allow. Yes, DFCO uses less gas, but you cannot glide for that long. There is a section when I am going to school... that if I time it right, I can NICE coast for almost two and a half miles into the school from the main road. DFCO would kill the speed about 3/4 of a mile into it. Then I would have to work my way through the gears again, which uses enough gas. They both have their advantages, and I use both when they are needed. I am not being a smart as when I say thanks for the insight either... It is people like you that help people get more from their cars, whether it be mileage or life... so thanks

Matt

[GeneW]

Originally Posted by drummerboy2004

Gene,

Thanks for all of the insight. Oh, and I use NICE-ON coasting if I am going downhill or need to coast longer than the DFCO will allow. Yes, DFCO uses less gas, but you cannot glide for that long. There is a section when I am going to school... that if I time it right, I can NICE coast for almost two and a half miles into the school from the main road. DFCO would kill the speed about 3/4 of a mile into it. Then I would have to work my way through the gears again, which uses enough gas. They both have their advantages, and I use both when they are needed. I am not being a smart as when I say thanks for the insight either... It is people like you that help people get more from their cars, whether it be mileage or life... so thanks

Matt

You're welcome.

Gene