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Thread: gas pedal "overtravel"?

  1. #16
    Registered Member Anchorman's Avatar

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    Quote Originally Posted by shadonoz View Post

    I was wondering if [and if so, how] the ECU reacts to the speed of pedal travel as well, as mentioned by Puyapim. I've heard rumors of that before.
    Not really. The PCM controls engine knock and flat spots under rapid acceleration and also heavy lurching at low speeds when the accelerator is released suddenly. I think you might be getting mixed up with rapid brake pedal inputs which will be interpreted as emergency braking and lower pedal input pressure. Try it on a quiet road at 30-40 mph. Hit the brake pedal as quick as you can and it will stand on its nose without the usual pedal force.

  2. #17
    Underutilized Member shadonoz's Avatar
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    Thanks for that! It doesn't address my question, but certainly showcases the complexity.

    Do you see anything titled "drive-by-wire control" or something similar? I think that might apply.

  3. #18
    Underutilized Member shadonoz's Avatar
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    Quote Originally Posted by Anchorman View Post
    Not really. The PCM controls engine knock and flat spots under rapid acceleration and also heavy lurching at low speeds when the accelerator is released suddenly. I think you might be getting mixed up with rapid brake pedal inputs which will be interpreted as emergency braking and lower pedal input pressure. Try it on a quiet road at 30-40 mph. Hit the brake pedal as quick as you can and it will stand on its nose without the usual pedal force.
    Not thinking about braking, just acceleration. For instance, will the engine respond to full throttle differently [more quickly] if the pedal is rapidly depressed rather than gently but quickly [squeezed?]. Stomped rather than stepped on perhaps.

    Maybe I just need to do more seat of the pants experimentation.

  4. #19
    Brownd3max

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    Funny how this detent "feel" in the go-pedal reminds me of my '69 Chevelle SS I sold last year- It had a built454 with an 850cfm double-pumper with mechanical secondaries. When you hit that resistance in that gas pedal, then mashed it, the secondaries snapped open, unleashing all 600hp, frying the 295/50's! Lotsa fun...

  5. #20
    Registered Member Xeler8ing's Avatar

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    More forcefull pressing should engage this function
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  6. #21
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    Quote Originally Posted by shadonoz View Post
    Not thinking about braking, just acceleration. For instance, will the engine respond to full throttle differently [more quickly] if the pedal is rapidly depressed rather than gently but quickly [squeezed?]. Stomped rather than stepped on perhaps.

    Maybe I just need to do more seat of the pants experimentation.
    Try this to get an example of how it works. Find a decent uphill stretch of road where you can do about 30-40 mph (no traffic around is best, of course). First time up the hill, just hold the accelerator pedal steady. It won't downshift, it'll feel like it's bogging down. Slowly press the pedal to maintain your speed. You'll get up the hill just fine, but it won't downshift. Now, do it a second time and when it starts to bog, "stab" the pedal quickly about 1/2 way down, let it return to where you had it before and then hold it steady. It'll downshift and hold that lower gear all the way up as long as you hold the speed steady. Now do it a third time and when it bogs, floor it and have fun as you continue to accelerate all the way up! This is a very fun and intuitive transmission.

  7. #22
    Underutilized Member shadonoz's Avatar
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    Quote Originally Posted by minnesotaart View Post
    Try this to get an example of how it works. Find a decent uphill stretch of road where you can do about 30-40 mph (no traffic around is best, of course). First time up the hill, just hold the accelerator pedal steady. It won't downshift, it'll feel like it's bogging down. Slowly press the pedal to maintain your speed. You'll get up the hill just fine, but it won't downshift. Now, do it a second time and when it starts to bog, "stab" the pedal quickly about 1/2 way down, let it return to where you had it before and then hold it steady. It'll downshift and hold that lower gear all the way up as long as you hold the speed steady. Now do it a third time and when it bogs, floor it and have fun as you continue to accelerate all the way up! This is a very fun and intuitive transmission.
    I live up a hill, and mine does not behave that way. If I hold the throttle steady, it WILL downshift when it thinks it's bogging down, and if I give it a just little throttle, it will downshift. It is, after all, an "automatic" transmission. If I want to stay in 4 and avoid a downshift, I have to run it in manual.

    But regardless, I'm just asking about the difference between when you squeeze the throttle vs stabbing it. Since this is a drive-by-wire system, I want to know if the system takes that into account and responds differently. I'm asking about the logic of the system.

  8. #23
    Registered Member Anchorman's Avatar

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    Quote Originally Posted by shadonoz View Post
    I live up a hill, and mine does not behave that way. If I hold the throttle steady, it WILL downshift when it thinks it's bogging down, and if I give it a just little throttle, it will downshift. It is, after all, an "automatic" transmission. If I want to stay in 4 and avoid a downshift, I have to run it in manual.

    But regardless, I'm just asking about the difference between when you squeeze the throttle vs stabbing it. Since this is a drive-by-wire system, I want to know if the system takes that into account and responds differently. I'm asking about the logic of the system.
    Mine would change down too.

    I think youíre thinking too hard about what you would like to see. The pedal is dumb hardware with springs and detent to give it the right feel. The business part is the APP (accelerator pedal position) sensor which is really a potentiometer just like a volume dial - the more you turn, the louder it goes. The car employs a canbus system. Itís basically a two wire system where every component is wired together. When a signal goes out from an ecu, all the components get it but only the one it is digitally addressed to responds. The pedal is just on the other side of the bulkhead or firewall as you call it and is the drivers ďvolume switchĒ. Iíve trawled the info today and the only pdf along those lines is attached. Interestingly, the pedal input would be suppressed if it stuck wide open by pressing the brake. That would stop that Toyota sticking throttle fiasco. Iím afraid thereís nothing quite as dramatic or romantic as it being sensitive to how it is pressed. Iíd love to help but it just isnít there.
    Attached Files Attached Files

  9. #24
    Underutilized Member shadonoz's Avatar
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    Quote Originally Posted by Anchorman View Post
    Mine would change down too.

    I think you’re thinking too hard about what you would like to see. The pedal is dumb hardware with springs and detent to give it the right feel. The business part is the APP (accelerator pedal position) sensor which is really a potentiometer just like a volume dial - the more you turn, the louder it goes. The car employs a canbus system. It’s basically a two wire system where every component is wired together. When a signal goes out from an ecu, all the components get it but only the one it is digitally addressed to responds. The pedal is just on the other side of the bulkhead or firewall as you call it and is the drivers “volume switch”. I’ve trawled the info today and the only pdf along those lines is attached. Interestingly, the pedal input would be suppressed if it stuck wide open by pressing the brake. That would stop that Toyota sticking throttle fiasco. I’m afraid there’s nothing quite as dramatic or romantic as it being sensitive to how it is pressed. I’d love to help but it just isn’t there.
    Perfect, thank you very much, Anchorman!

    Actually, I was just trying to confirm or deny what I have often heard about the speed of depression of the pedal being a factor. You have pretty well debunked that, at least for the CX-5. It now enters the category of urban legend for me. I didn't want it to be true... I like to KISS! Extra complexity leads to increased failures and unintended consequences.

  10. #25
    Registered Member Xeler8ing's Avatar

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    It's just a pedal. Push it gently, punch it hard etc and the CX-5 reacts accordingly. It [computer module(s)] has enough smarts to work as intended.
    Last edited by Xeler8ing; 07-11-2018 at 05:51 PM. Reason: Typo Fix
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    Quote Originally Posted by Anchorman View Post
    Mine would change down too.

    I think you’re thinking too hard about what you would like to see. The pedal is dumb hardware with springs and detent to give it the right feel. The business part is the APP (accelerator pedal position) sensor which is really a potentiometer just like a volume dial - the more you turn, the louder it goes. The car employs a canbus system. It’s basically a two wire system where every component is wired together. When a signal goes out from an ecu, all the components get it but only the one it is digitally addressed to responds. The pedal is just on the other side of the bulkhead or firewall as you call it and is the drivers “volume switch”. I’ve trawled the info today and the only pdf along those lines is attached. Interestingly, the pedal input would be suppressed if it stuck wide open by pressing the brake. That would stop that Toyota sticking throttle fiasco. I’m afraid there’s nothing quite as dramatic or romantic as it being sensitive to how it is pressed. I’d love to help but it just isn’t there.
    Could be what some people see as a pedal response is due to the transmission shift points are somewhat flexible... There is a documented reset procedure for re-learning them (and I've done it) - it's based on the pedal. In theory it seems like it would be possible to have the car respond differently depending on how the pedal is pressed, but this would be documented. The complexity there might also cause drivability issues.

  12. #27
    Registered Member Xeler8ing's Avatar

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    It learns your driving pattern and adjusts accordingly. If you baby it all the time, it will respond in kind. Yes you are correct that it can be retrained, the transmission that is.
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  13. #28
    Registered Member Anchorman's Avatar

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    Quote Originally Posted by craigo View Post
    Could be what some people see as a pedal response is due to the transmission shift points are somewhat flexible... There is a documented reset procedure for re-learning them (and I've done it) - it's based on the pedal. In theory it seems like it would be possible to have the car respond differently depending on how the pedal is pressed, but this would be documented. The complexity there might also cause drivability issues.
    This is a very good point. When driving an auto, it does of course respond differently by either driving it hard or driving it steady. As X8 has eluded, it will maintain low gears and rev high if you cane it but then go back to keeping the revs low soon after resuming a more relaxed style. I suppose that could be interpreted as pedal feel as you certainly wouldn’t get it with a manual transmission. It would react exactly as you put in.

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