Using DFCO to increase your MPG

[STC]

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]

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]

Originally Posted by micahsyl

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]

Originally Posted by micahsyl

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.

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]

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]

Originally Posted by advocate

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]

do the spark plugs still fire as well?

[Yaris Hilton]

Yes.

[KrazyDawg]

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]

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]

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]

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!

[Maxh91]

Originally Posted by imjustagirl8_05

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!

-Yes you yaris have DFCO
-As your yaris is a 2007, you need to be in 3th or lower to activate the DFCO.
The 2008 and newer can do DFCO in every gear.
-You car need to be in gear (L,2,3) to activate the DFCO AND you need to be above 1100RPM

[Yaris Hilton]

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]

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]

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]

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]

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.