Not so spontaneous, intended acceleration - Toyota Yaris Forums

sbergman27 · 03-15-2010, 04:57 PM

OK. So all my previous cars have had carburetors... with multiple barrels which operate in a tiered fashion as you depress the pedal farther. On my old cars with Rochester Quadrajets, I've always been slightly annoyed that it seems you have to push the pedal way down before you get a reasonable percentage of total engine power.

With the Yaris, I have the opposite complaint. A tiny depression of the accelerator results in a large fraction of the engine's capacity being called to bear. And the automatic transmission also acts as though I've indicated that I want to really fly.

Now, with the drive by wire throttle that we have, the engineers could have specified any curve that they wanted. I wonder why they went with this? And what is "this"? Is the throttle rotation, in degrees, linear with respect to the depression of the pedal? Is the cross-sectional area exposed by the throttle plate linear with pedal depression? Or is the curve completely different? And if so, why was that curve chosen?

Or am I the only one who would prefer a more "laid back" calibration?

-Steve

Loren · 03-15-2010, 05:23 PM

It's a "learning" system. You may want to try resetting it to default so that it can learn YOUR driving habits.

The throttle pedal is definitely not linear. Think of it as a "demand" pedal. Where you place your foot and/or how quickly you move it are the inputs that the ECU uses to assess what you want it to do. It then uses that input and many others to determine how much to open the throttle, how to set the valve timing and ignition timing, whether to go rich (open loop) or use the O2 feedback to keep the mixture stoich, etc.

Most people complain about the opposite problem, the DBW system is not sensitive enough. And maybe that's what you're feeling? It's not sensitive to a small input, so you give it a larger one... which it then responds to.

Give it time, it should learn you and you will learn it... you'll get used to it.

Yaris Hilton · 03-15-2010, 05:40 PM

I've noticed a trend in recent years to make throttles very quick responding in the first bit of travel. It's a cheap way to make drivers think a car is very powerful and speedy. "It wants to leap ahead when I barely give it the gas!" If they have to push the pedal halfway down to get the same response, average drivers will conclude the car lacks power.

sbergman27 · 03-15-2010, 05:49 PM

Quote:

Originally Posted by Loren

It's a "learning" system. You may want to try resetting it to default so that it can learn YOUR driving habits.

My accelerator pedal is heuristic!?!?!?!?!?!?

Oh my. I was not expecting that.

What's the easiest way to go back to the defaults? I've driven 2-1/2 weeks and about 6,000 miles (yeah, I drive a lot) and have not noticed any change in its behavior.

-Steve

Edit: The *very* first bit of pedal travel does not seem to get any response at all, so I push it a little farther (not much) until I do get a response. When it kicks in, that's when it seems overly sensitive. Is that what you are referring to?

Yaris Hilton · 03-15-2010, 05:57 PM

The only learning behavior I've noticed is in transmission shift points. It trains very quickly, usually in a day's driving. No special action is needed for resetting, it adjusts to your driving style as you go. Thrash it and it'll wind up farther before shifting and downshift quicker. Drive it like a hypermiler and it'll lug along shifting when it really has to.

Altitude · 03-15-2010, 05:58 PM

Quote:

Originally Posted by sbergman27

My accelerator pedal is heuristic!?!?!?!?!?!?

Oh my. I was not expecting that.

What's the easiest way to go back to the defaults? I've driven 2-1/2 weeks and about 6,000 miles (yeah, I drive a lot) and have not noticed any change in its behavior.

-Steve

Disconnect the battery for a period of time (just how long I'm not sure as I've seen many different values mentioned.)

FWIW - Mine is a manual and I find just the opposite in that I have to goose it a bit to avoid stalling when letting the clutch out. I've considered doing the reset and stomping on it for a while to see if the ECU adapts to the new style. Let us know how your experiment works out.

Loren · 03-15-2010, 06:04 PM

If you've driven 6k in 2.5 weeks, it's probably 95% highway miles, and the ECU isn't "learning" very much. A week of stop-and-go "city" driving would really teach it something.

I'm pretty sure that disconnecting the battery for a bit will clear the short term ECU settings. Seems to work well for people who are doing things like swapping headers and such to get the car to re-learn it's new "self".

You know that the Yaris factory service manual is available online, right? You can read and learn a lot from them.

sbergman27 · 03-15-2010, 06:12 PM

Quote:

Originally Posted by Loren

If you've driven 6k in 2.5 weeks, it's probably 95% highway miles,

At least. And my Yaris experience has been a bit of an unexpected whirlwind affair. (Impulse buy, in a way.) I'm so used to knowing all the intimate details about my cars like the back of my hand... but only determined that the transmission is a sealed unit, using Toyota WS fluid, earlier today. The proper antifreeze is a non-silicate, hybrid organic acid formulation. (Not to be confused with a hybrid organic acid formulation with silicates, or a non-hybrid organic acid formulation with or without silicates.) The list of surprises goes on. What an interesting adventure this is turning out to be.

Perhaps I should change my name to Alice, for now?

And no. I didn't realize that the FSM was available online. I'll have a look. I'm sure that it will be most interesting. Curiouser and curiouser, said Alice...

-Steve

Reeves360 · 03-16-2010, 03:42 PM

Quote:

Originally Posted by sbergman27

OK. So all my previous cars have had carburetors... with multiple barrels which operate in a tiered fashion as you depress the pedal farther. On my old cars with Rochester Quadrajets, I've always been slightly annoyed that it seems you have to push the pedal way down before you get a reasonable percentage of total engine power.

With the Yaris, I have the opposite complaint. A tiny depression of the accelerator results in a large fraction of the engine's capacity being called to bear. And the automatic transmission also acts as though I've indicated that I want to really fly.

Now, with the drive by wire throttle that we have, the engineers could have specified any curve that they wanted. I wonder why they went with this? And what is "this"? Is the throttle rotation, in degrees, linear with respect to the depression of the pedal? Is the cross-sectional area exposed by the throttle plate linear with pedal depression? Or is the curve completely different? And if so, why was that curve chosen?

Or am I the only one who would prefer a more "laid back" calibration?

-Steve

I have the same issue and have reset my car multiple times. Also pushing down on the pedal feels like there is almost no resistance when compared to a pedal in an older car.

I'm assuming they made it this way on purpose because they felt people would over rev the car when switching from normal gas pedals.

03-15-2010, 04:57 PM	#1
sbergman27 Drives: 2008 Yaris Sedan Join Date: Feb 2010 Location: Oklahoma City, OK Posts: 323	Not so spontaneous, intended acceleration OK. So all my previous cars have had carburetors... with multiple barrels which operate in a tiered fashion as you depress the pedal farther. On my old cars with Rochester Quadrajets, I've always been slightly annoyed that it seems you have to push the pedal way down before you get a reasonable percentage of total engine power. With the Yaris, I have the opposite complaint. A tiny depression of the accelerator results in a large fraction of the engine's capacity being called to bear. And the automatic transmission also acts as though I've indicated that I want to really fly. Now, with the drive by wire throttle that we have, the engineers could have specified any curve that they wanted. I wonder why they went with this? And what is "this"? Is the throttle rotation, in degrees, linear with respect to the depression of the pedal? Is the cross-sectional area exposed by the throttle plate linear with pedal depression? Or is the curve completely different? And if so, why was that curve chosen? Or am I the only one who would prefer a more "laid back" calibration? -Steve Last edited by sbergman27; 03-15-2010 at 05:09 PM.

03-15-2010, 05:23 PM	#2
Loren What? Drives: 2007 Yaris LB Join Date: Nov 2008 Location: Safety Harbor, FL Posts: 1,006	It's a "learning" system. You may want to try resetting it to default so that it can learn YOUR driving habits. The throttle pedal is definitely not linear. Think of it as a "demand" pedal. Where you place your foot and/or how quickly you move it are the inputs that the ECU uses to assess what you want it to do. It then uses that input and many others to determine how much to open the throttle, how to set the valve timing and ignition timing, whether to go rich (open loop) or use the O2 feedback to keep the mixture stoich, etc. Most people complain about the opposite problem, the DBW system is not sensitive enough. And maybe that's what you're feeling? It's not sensitive to a small input, so you give it a larger one... which it then responds to. Give it time, it should learn you and you will learn it... you'll get used to it. __________________ ----------------------- Loren@InvisibleSun.org -----------------------

03-15-2010, 06:04 PM	#7
Loren What? Drives: 2007 Yaris LB Join Date: Nov 2008 Location: Safety Harbor, FL Posts: 1,006	If you've driven 6k in 2.5 weeks, it's probably 95% highway miles, and the ECU isn't "learning" very much. A week of stop-and-go "city" driving would really teach it something. I'm pretty sure that disconnecting the battery for a bit will clear the short term ECU settings. Seems to work well for people who are doing things like swapping headers and such to get the car to re-learn it's new "self". You know that the Yaris factory service manual is available online, right? You can read and learn a lot from them. __________________ ----------------------- Loren@InvisibleSun.org -----------------------

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03-15-2010, 05:40 PM	#3
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	I've noticed a trend in recent years to make throttles very quick responding in the first bit of travel. It's a cheap way to make drivers think a car is very powerful and speedy. "It wants to leap ahead when I barely give it the gas!" If they have to push the pedal halfway down to get the same response, average drivers will conclude the car lacks power.

03-15-2010, 05:57 PM	#5
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	The only learning behavior I've noticed is in transmission shift points. It trains very quickly, usually in a day's driving. No special action is needed for resetting, it adjusts to your driving style as you go. Thrash it and it'll wind up farther before shifting and downshift quicker. Drive it like a hypermiler and it'll lug along shifting when it really has to.