Throttle Lag On DBW

[Yaris Hilton]

Originally Posted by bronsin

Not sure what that is. The problem is: you push on the gas pedal and the car doesnt move until you push harder. Just how hard takes a while to figger out. My wifes 05 Camry is the same way. My 01 ECHO (cable) doesnt do that.

DFCO is Deceleration Fuel Cutoff. Whenever you're coasting with the engine turning much above idle speed, the fuel is completely cut off for zero emissions and zero fuel consumption. That of course drags the car down a bit faster than coasting with an idling engine. As you press the gas pedal, there's a slight free play before it recognizes that you want some power, and when the fuel cuts on it's slightly above the idle power level. You'll feel a small surge forward, and when you back off and the fuel cuts off again, there's a sudden slight deceleration. Like I said, if you're cruising slowly on level ground where very little power's needed, you'll feel it surging and dragging as it cuts the fuel on and off. That's normal behavior. The old Echo's ECU was much less sophisticated and didn't have this feature. Automatic Yarises up through about the middle of the 2007 model year didnt have it in Drive, either.

[silver_echo]

Originally Posted by Yaris Hilton

DFCO is Deceleration Fuel Cutoff. Whenever you're coasting with the engine turning much above idle speed, the fuel is completely cut off for zero emissions and zero fuel consumption. That of course drags the car down a bit faster than coasting with an idling engine. As you press the gas pedal, there's a slight free play before it recognizes that you want some power, and when the fuel cuts on it's slightly above the idle power level. You'll feel a small surge forward, and when you back off and the fuel cuts off again, there's a sudden slight deceleration. Like I said, if you're cruising slowly on level ground where very little power's needed, you'll feel it surging and dragging as it cuts the fuel on and off. That's normal behavior. The old Echo's ECU was much less sophisticated and didn't have this feature. Automatic Yarises up through about the middle of the 2007 model year didnt have it in Drive, either.

really? my 01 5spd has dfco, and i never really notice when it switches... the only reason i am sure that i have dfco is from one of the hypermiling threads... the "shut-off" test...

[Yaris Hilton]

I don't think my daughter's '01 with AT did. (At least in "Drive.") But you'll be able to feel it if it does. It's really pretty subtle, not a great lurch. You have to pay attention to it.

[kenora]

Originally Posted by Yaris Hilton

I don't think my daughter's '01 with AT did. (At least in "Drive.") But you'll be able to feel it if it does. It's really pretty subtle, not a great lurch. You have to pay attention to it.

Mine definately does it and it took awhile to realize what was going on, its most noticeable with cruise on coasting down a slight decline around 60 kph, it will accelerate (going down hill) just a bit to a speed which is above the set speed (60) then go off throttle, that causes DFCO to kick in, it decellerates to a speed just below the set speed and wants to speed up so DFCO is cancelled, fuel flows again and car speeds up to set speed at which point with the engine running it goes a bit over the set speed and DFCO cuts off fuel. The process continues until either the hill gets steep enough that it can stay in DFCO at or above the set speed or I get in the flats and the engine runs as normal.

Pretty subtle but you can "feel" it cut in and out.

[bronsin]

Originally Posted by Yaris Hilton

Whenever you're coasting with the engine turning much above idle speed, the fuel is completely cut off for zero emissions and zero fuel consumption.

If that were true the engine would stop running. The engine has to have fuel to idle. But what you say is interesting. I had a BMW F650 2001 which, at times, would not idle when you came to stop at a light. It would start and run if you gave it more throttle while cranking, but it would not idle if you relaxed the throttle to the idle position. Turn the ignition off and on, start the engine and poof, it ran flawlessly. Until the next time. I could not fix it and neither could BMW. (their main effort was to blame me for not pulling the clutch in in time)
But maybe it had something similiar to what you describe. Thats the problem with all this gee whiz neato stuff. When it breaks its pretty hard (if not impossible) to fix. Some say they dont notice this problem so maybe theirs is working properly.

[Yaris Hilton]

Originally Posted by bronsin

If that were true the engine would stop running.

Not at all. It's engaged to the driveline and is kept turning by the car's momentum. Indeed, if you turn the switch off with the car in gear and moving, the engine will keep spinning till the car eventually stops.

DFCO is very common in modern automobiles.

The fuel cuts back in at idle power level when the engine speed gets down to some preset level just above idle.

[Tamago]

Originally Posted by Yaris Hilton

Not at all. It's engaged to the driveline and is kept turning by the car's momentum. Indeed, if you turn the switch off with the car in gear and moving, the engine will keep spinning till the car eventually stops.

DFCO is very common in modern automobiles.

The fuel cuts back in at idle power level when the engine speed gets down to some preset level just above idle.

i'd like to add that this only happens on decel (per my wideband o2 anyway)

[bronsin]

Originally Posted by Yaris Hilton

Not at all. It's engaged to the driveline and is kept turning by the car's momentum. Indeed, if you turn the switch off with the car in gear and moving, the engine will keep spinning till the car eventually stops.

DFCO is very common in modern automobiles.

The fuel cuts back in at idle power level when the engine speed gets down to some preset level just above idle.

Hmm you said "turn the (ignition?) switch" off. I agree it would stop. But we're talking about taking your foot off the gas pedal and supposedly the fuel is cut off. If I took my foot of the gas of my Yaris it would slow down sure. But it would eventually go about 5 mph, not stop.

[alhope34]

Originally Posted by bronsin

Hmm you said "turn the (ignition?) switch" off. I agree it would stop. But we're talking about taking your foot off the gas pedal and supposedly the fuel is cut off. If I took my foot of the gas of my Yaris it would slow down sure. But it would eventually go about 5 mph, not stop.

That's because DFCO only works above 1100 rpm, or around there. Once you get below that rpm, it starts putting gas and spark back to the engine so it wouldn't stall. Obviously it would be a marketing horror to try and sell a car that stalls every time you take your foot off the gas. My Mazdaspeed 3 also has DFCO and I can never feel any difference when it goes on or off.

[bronsin]

Originally Posted by alhope34

Obviously it would be a marketing horror to try and sell a car that stalls every time you take your foot off the gas.

My 2001 BMW F650 motorcycle, thankyou very much BMW!

[Tamago]

Originally Posted by bronsin

My 2001 BMW F650 motorcycle, thankyou very much BMW!

shoulda bought an R bike

[Tamago]

Originally Posted by bronsin

If I took my foot of the gas of my Yaris it would slow down sure.

i think this deserves a captain obvious award.

[alhope34]

Originally Posted by Tamago

i think this deserves a captain obvious award.

Ahahaha, agree'd!

[bronsin]

Originally Posted by Tamago

i think this deserves a captain obvious award.

Erm...if you take something out of context yeah you could say that about most anything...

[Tamago]

Originally Posted by bronsin

Erm...if you take something out of context yeah you could say that about most anything...

award #2 you're on a roll!


i'm glad you can take the joke without getting upset though, that shows character !

[Yaris Hilton]

Originally Posted by bronsin

Hmm you said "turn the (ignition?) switch" off. I agree it would stop. But we're talking about taking your foot off the gas pedal and supposedly the fuel is cut off. If I took my foot of the gas of my Yaris it would slow down sure. But it would eventually go about 5 mph, not stop.

Because the ECU is monitoring the engine speed, and as I said above, when it gets down to a preprogrammed speed a little above normal idle (about 800 RPM by my tach), the fuel cuts back on with the engine running at idle power. Those Toyota engineers are pretty smart fellows. They figured we don't want our engines to just die every time we coast. On my automatic, the torque converter stays locked down to the point where the engine cuts back on. It locks (as judged by the RPM and speed staying tightly linked together) even at rather low speeds cruising around town. Mine has "learned" that I like to drive in economy mode.

[bronsin]

Originally Posted by Yaris Hilton

It locks (as judged by the RPM and speed staying tightly linked together) even at rather low speeds cruising around town. Mine has "learned" that I like to drive in economy mode.

How long did it take for the learned behavoir to kick in? My Yaris is 850 miles and two months old. Im pretty happy with the 35-36 mpg its been getting. Considering I only drive it 6 miles to work and back. But maybe theres more?

[Yaris Hilton]

Originally Posted by bronsin

How long did it take for the learned behavoir to kick in?

Couple of days at most. When I "borrowed" my daughter's 2007 S, which is used to her and her boyfriend driving it a bit more aggressively than I do, it started acting like mine pretty quickly. It was built late in the 2007 model year and has DFCO in Drive just like mine.