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Thread: Drive by wire and throttle respoonse

  1. #1
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    Drive by wire and throttle respoonse

    I would like to know if the devs over at HPT have thought about adding a feature to adjust the accelerator pedal input smoothing?.. I am pretty sure that there is a buffer of some sort that holds a specified number of readings taken from the accelerator position sensor and it averages that buffer and that is what gets used to set the throttle.

    Having a way of adjusting the size of that buffer would be a really nice feature to have especially on vehicles that have drive by wire when it was still a newish technology. The ECM's were really not up to snuff in terms of speed and the buffers were to large so you ended up with throttle response problems. Attaching a device to the accelerator position sensor that offsets the value is not the proper way to go about doing it, and those things don't do a thing when you mash the pedal to the floor.


    I do not know how large the buffer is, what I do know is that my 2008 Pontiac Solstice takes quite a long time for the throttle to reach 96% when I mash the accelerator to the floor. I am not taking 2 second, closer to 5 or 6 seconds if not more. I would have to go back and check.

    As an example, If you have a buffer of say 40 values and all of the values are at 30 the average is going to be 30. then you add a value of 90 to that buffer. the averaged amount is going to be 31.5 it is gong to take 39 more readings of 90 before the average is a 90. That is going to cause a lag in the throttle. This is done to help improve gas mileage because it smooths out fluctuations caused by a persons foot. I don't think the people using HP Tuners care to much about fuel efficiency.

    I know that I would rather have as close to real time throttle response over MPG.

    You can thank the EPA for this wonderful gift...

    I would think that there has to be a way to adjust the size of the buffer or even eliminate it completely..

  2. #2
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    Since you didn't attach your tune file I grabbed some random Solstice file from the repository to get an idea of what you have available to work with.

    E69(?) seems to be very limited. V8 files have all kinds of stuff for Electronic Throttle.

    However it would be great if you could upload a file so somebody could see what changes you've made (and if they helped or did nothing) at Engine > Torque Management > General > Tip-in Limiting.

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    OK I attached the tune file, a log for that tune and also the scanner layout and channels files.

    The 5-6 second throttle response issues are when I let off the accelerator, The ECM actually continues to open the throttle body further for upwards of 1-1.5 seconds after I have let go of the accelerator. and it takes another 4-5 seconds after that before the throttle closes.

    On acceleration from peak of the accelerator pedal position to peak of the throttle position is it typically 1 - 1.5 seconds delay between the 2.
    Attached Files Attached Files

  4. #4
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    Does it do that for real, or are you inferring that it's doing that based on the timing of things you see happening in the logs? Because I have a hard time believing that it wouldn't be a massive scandal/recall/breaking news if that was the intended behavior and GM allowed it to leave the factory like that. Logs can be misleading, some channels update faster than others and it can look like things happen out of order when they really don't.

    I see a whole bunch of stuff changed in that tune, and not a lot of actual tuning. I can't make sense of the reasoning behind most of the changes. I would first return the tune to stock (or as stock as possible, allowing for any hardware changes) and see if it starts behaving normally.

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    I can't go back to the stock tune because of changes that have been made to the engine performance wise. The car would not run properly.

    There has always been a throttle response problem with these cars and also with the 2.4 N/A version of the car. It is a very noticeable problem while driving the vehicle. I do not understand as to why there would be logging delays as the information for the throttle position, accelerator position, vehicle speed, and RPM should be broadcast on the high speed can bus, there shouldn't be a need to send a request to the BCM on the low speed bus and then have the BCM reply.... I would hope that the HP tuners scanner is not using OBDII requests to collect this time sensitive information that a user is supposed to use to tune a vehicle. That would completely blow my mind if that is what is being done and it would make dialing in a tune hard to do I would imagine.

    I personally do not feel that I have enough knowledge to be able to safely tune a vehicle, There is a place that is doing the tune remotely, they specialize in these cars and have been doing the tunes for years. That being said, no person tuning a vehicle knows everything about tuning, they are always learning new tricks or how to adjust something. So having more eyes take a look at it there could be something that is getting missed or not being done...

    Also if it was a "delay" in the logging then the delay would be a constant, it would be the same across the entire log. the offset from the delay would be easily seen. This is not the case. the throttle delay seems to change with how much the accelerator position is changing from previous readings. If the change is large the delay seems to be less, if the change is small it seems to take longer for the change to be realized in the throttle position. This type of a phenomenon would be caused by a smoothing algorithm in the ECM, which is the reason why I asked if there is a way to alter this portion of the ECM to be able to give the driver a closer to real time throttle response.

    On my car the turbo has been changed on the vehicle, it is a significantly larger turbo then what the stock one was. The new setup now uses an external waste gate instead of an internal one. the original turbo has a 100% recirculating valve, there is now 50/50 valve that vents some of the pressure to atmosphere and recirculates the rest of it, the IC has been changed and has some 250% more cooling capacity over the stock one. map sensor has been replaced as well as the charge pipe pressure sensor to one that has a higher upper limit, charge pipes have been replaced and also the intake. The cat has been replaced with a high flow. There are also a lot of other changes made but nothing that would need to be accounted for in the tune.

    Most vehicles that were made with drive by wire during that era have throttle response problems. It is not a new thing. This was corrected in later releases of the cars by changing the ECM. The Solstice was not made long enough to have that happen. I used to own a 2005 Lotus Elise. I specifically bought the 2005 MY because the 2006 MY has throttle response problems because this was the first year they had drive by wire in the car. the 05's were mechanical.

    I know that these ECM's work on a torque demand system, they learn away any performance upgrades unless the ECM gets tuned. There are things programmed into it that intentionally reduce output power, the differential in the Solstice is not up to the task of handling the output power from the engine when "launching" the car. The ECM reduces the output power of the engine. I believe it does this until the last half of second gear, it is done so the diff has less of a chance if failing. From what information I am able to locate in the internet about these ECM's there are some 2500 tables in these things where most other ECM's have what??? 250 tables or there about.. There is a very small amount of things that can be altered via HP tuners. There are other companies that offer tunes and have access to more then what HP Tuners provides but they are "canned" tunes and not a DIY type of solution. I live at 8500 foot altitude, I need a custom tune done to get the most possible out of the setup I have.

    after 12 years of this ECU being around (and they are used in several GM vehicles) I would have thought by now there would be more available form HP Tuners. It is not a matter of having to reverse engineer them anymore, that work has already been done the knowledge is there. it needs to be added to HP tuners to allow access to them. You had stated that there are more parameters available for the V8's for adjusting throttle controls. why is that? I am willing to bet there are far more Chevy Cobalts (use the same ECU as the Solstice) that have been sold then say a corvette of the same era.. Same thing goes for the 2009-2011 Chevy Camaro with the V6 in them. once again same ECU. Cadillac CTS is another. These cars are outside of their warranty and people are more then willing to spend the money to tune them. they are also cheap to buy so there is more money available to upgrade them. This is what is taking place with the Solstice. they are cheap and the people buying them are the 40 and older crowd and have the money to put into them. HP Tuners is not used as often as it should, the reason being is the limited access. at least twice a week there is someone new on the forum and they just bought a Solstice or a Sky and are asking about tuning the car, or the throttle response. HP tuners is not mentioned. It should be the go to tuning solution especially after 12 years since the release of the car. I know that HP tuners has lost popularity over the years, most likely due to the fact that they offer access to only some functions and then they call it done and do not continue to add more. They get enough so they can add a vehicle to their compatibility chart and then development for that platform/ECU becomes stagnant.

    I would switch out the ECM for something different if there was anything that would work that was OBDII compliant. I have not been able to locate anything that would work.

    The "canned" tune options get locked. so If I wanted to get the car on a Dyno and have a shop make some adjustments to the tune it cannot be done. This is a deal breaker for me. The other thing is the whole "tool rental", I would not have the ability to flash a tune that is made for sea level and then a different one for high altitude. Only the manufacturer of the canned tune is able to do it, another deal breaker.


    As far as the "scandal/recall" thing is concerned. Never gonna happen. The Solstice uses the exact same HVAC system that the Hummer H3 uses, the H3's have been recalled for a meltdown of the wiring harness to the blower motors. This same thing is happening to the Solstice/Sky, these cars were not included in the recall and we have been fighting to get it included with no luck. The recall for the passenger presence sensor for the airbag, the fix... a piece of duct tape, and guess what that works for 2 years but since the recall has been performed on the car the owner of the car how has to foot the 1000.00 bill for replacing the sensor. This is what should have been done in the first place. Unless someone gets injured or dies it's not going to get fixed. and also because of how GM trolls through the internet looking for people that post information about their systems and if they find someone they send them a cease and desist letter for copyright or trade infringement, no one is going to be able to provide the NHTSA with concrete data about the problem. There was a group of people that hacked OnStar they could control every aspect of the car except for steering (the ability didn't exist at the time), this group privately told GM about it instead of going public and causing all kinds of issues for GM. GM's response.. The information about it got buried and there was probably a gag order put in place on the individuals that found the problem and then GM took their sweet time fixing it, 10 years.

  6. #6
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    Jesus. Have you ever owned a Fiero? (anyone who has known Fiero owners will know what I'm getting at here)

  7. #7
    Senior Tuner 10_SS's Avatar
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    Jeep Grand CHerokees continue accelerating 1-2 full seconds after you let off the throttle. It's just delay, and annoying. Not a scandal, LOL

    Regarding the "buffer", on 2010 Camaro E38, there is a table called "Opening Rate". High numbers make it respond instantly, lower numbers make it respond slower, I actually prefer a bit slower for the opening rate, but this does not affect the closing rate.

    You may want to ask if they have a "closing rate" table. There may be one, if HPT can find it, or wants to find it, that is the question.

    Logging delays come from the HPT scanner methods not being optimized to the ECU, is all, nothing else. Like my 2020 Silverado, not optimized, things like RPM update very slow. Same with the tune file not showing as many available parameters as others, HPT just hasn't spent the same amount of time on them.

    Regarding your throttle opening/closing rate, that data looks choppy, if you zoom in, it looks like stairs, where it moves a bit, then stops, moves more, then stops, etc. The logging rate in the raw data looks good, but the value is stepped like that, hard to say if the blade is acting that way.

    Also noticed you have some settings for ETC Load Damping, you may want to adjust those for now. One in particular, is ECM 33040, says set to maximum to disable, your values are as low as 10%. In my opinion, you do want some ETC smoothing, or delay, at least with Whipple superchargers, as I was getting some pretty severe boost spikes wtih stock rates, set very fast.

    as Blindsquirrel says, you can change one thing seemingly not realted to TPS, but the TPS can start acting strange, and that could be due to the torque management or this Load Damping stuff. I reduced the rate of my TPS blade just a bit, and now between shifts at high RPM, I get full on delay before the TPS blade starts to open sometimes, and sometimes not. Obviously not related to Opening Rate, but this did not happen with stock full speed opening rate, and it is not consistent, but still not a big problem, it actually helps me not abuse my clutch and driveline as much, so not worried about it.
    Last edited by 10_SS; 4 Days Ago at 09:17 AM.
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  8. #8
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    Quote Originally Posted by blindsquirrel View Post
    Jesus. Have you ever owned a Fiero? (anyone who has known Fiero owners will know what I'm getting at here)
    Hahahahaha. I get it. It was real. I have personally experienced 4 separate instances. Fun stuff.

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    Thank you @10_SS, I didn't think I was imagining it, I was starting to worry there for a minute. It drive me crazy having to wait 1-2 seconds before the car responds to what I am doing with the pedal.

    I Thought that the stepping may be what the scanner software does to fill in data gaps.. if the car responds to the accelerator position faster then it does for the throttle position there could end up being gaps in the data for the throttle position so what the software does in those cases is it fills the gap with the previous reading. This would cause a flat spot in the graph.