Diver Demand Tables

I am looking for some clarification on what the driver demand tables on a C7 do.

Robert,

The driver demand tables function similarly across a broad range of GM vehicles so this info will hopefully help you and others.

One axis is generally engine speed or vehicle speed. This won't always be clearly labelled, but if it is engine speed, you'll see values up into the thousands typical of engine speed. If the axis values only go up to a number under 1000, it's likely vehicle speed. As an example a C7 z51 auto has x axis values from 0-260, so we can safely assume this is vehicle speed not engine speed.

Then the other axis is accelerator pedal position, in percent, from 0 (pedal not pressed) to 100% (pedal pressed all the way down).

The z data, or main table data between the axes, is related to an amount of torque you're requesting at that combination of engine/vehicle speed and accelerator position. Depending on the vehicle, the z data may look like torque values in lb ft, or the values may trend in similar fashion, but not resemble engine torque values you're expecting.

Whether the z data values look like reasonable lb ft values or not, I suggest reviewing the trends across the table as a starting point. Typically you'll see values increase from low to high as accelerator pedal input increases from low to high. Trends with changing RPM and vehicle speed will vary more between vehicles.

Next if the vehicle has multiple driver demand tables, see if they're different, then specifically what is different. Drive in different modes to see what you like and don't like about each one. I suggest logging while doing so you can go back and see what engine speed, vehicle speed, accelerator pedal position (APP) you were at when you liked one more more than another. Then you can go back to the tables and see how the values differed between modes.

After that, the next step is making changes yourself, at your own risk. You'll need to be extremely careful because a mistake made here can cause unintended, unwanted, and unsafe acceleration. Ideally you would perform all testing of these changes on a dyno for safety, but by making careful appropriate small incremental percent changes, some people do have success altering this without a dyno. Again, please be careful. Avoiding increasing z data in 0% APP areas would be a good start so when you're expecting negative torque, you still get it.

Regardless of the z data units, if your personal preference suits a couple percent more engine output at a given speed and APP, add that percentage to that cell in the cable. If you want a few percent less engine output in an area, subtract a few percent.

I suggest always making sure z data values are increasing as APP is increasing. For example you don't want to have 350 at 40% APP and 400 at 30% APP because when you reduce APP while driving that would increase engine output, when you were likely expecting a decrease.

Again, be careful, and if you have a specific question, please let us know.

Thank you for the response. I am looking at these tables for two reasons. The first is the famous C7 throttle lag. I have a 2015 Camaro and the throttle response is much sharper than in my 2014 corvette. I have played with the DD tables and it has helped this some but not perfect. The second reason is that when using rev match (manual) the downshift is perfect but it also affects the behavior when shifting up. The RPM will hang a bit. I do not see any way to adjust the rev match behavior in the tune as I can with the Gen 5 camaro.

Robert,

Increasing engine output with throttle input is certainly possible with adjustment of that system, so I think with some more time you'll achieve your desired result. The throttle can physically move quicker than you'd ever want it to, so it's a matter of calibration.

I'm not clear what you're describing in the second half of your comments, but if you increase TQ desired in low APP areas, you will get rev hang regardless of up or downshift.

If you haven't adjusted those areas, some measure of rev hang often exists in stock form for emissions purposes.

Then some measure of rev hang is due to the mechanical nature of inertia of the internal components combined with clutching in which removes load from the engine.

With more specifics on what you've adjusted and are asking, I may be able to provide further info.

Another things to keep in mind, which might help with your mention of auto rev matching, is that sort of factory function, as with any function, hasn't necessarily been reverse engineered and then exposed in the software you're using to calibrate a factory PCM with. A function or set of tables may exist on a particular ROM, but may not be able to see/alter the functionality causing the behavior you're wanting to change. I suggest work with what you do have access to, and you'll figure out whether the change you want to achieve is possible or not with your current software access.

There's a great deal of ECU code and tables which are not exposed for adjustment in these ECUs. Tuning software providers try to focus on the functionality their customers are most likely to want first, then make additions based on feature requests as they have time and customer interest to warrant it.

Best of luck in your adjustments!

This is very helpful. Why the hell did I wait so long to sign up with HPA. Pouring through endless forums of misinformation was killing me.

I did increase map A a bit from 16 - 38. Perhaps I have gone the wrong way and need to go back to stock and pull a little out. It only hangs when rev match is on so I know for sure its a byproduct of this function.

I am attaching my tune for reference.

Robert,

I'm glad to hear you're enjoying HPA!

If you post the stock file as well, then we can more easily identify where you've made changes.

A trick that might help, is deciding on a behavior you'll execute to indicate you liked how the car responded vs. didn't like it, which is easy for you to find when you review datalogs. For example if you want less output in an area next time, you could tap the brake pedal 3x quickly to note that. You would datalog brake switch to see that later. If you log clutch switch, accelerator pedal, you can clutch in and stab the accel pedal quickly after a vehicle behavior where you want more response next time.

Whatever "code" you come up with to help you identify when behaviors occurred, and which direction you wanted to change them, this generally helps avoid editing areas you didn't actually want to, or in the opposite direction you intended.

You can also wire switches or buttons in and use the pro features with HPT to log them as a potentially more elegant way of noting things for later review in logs.

That is a great suggestion. I will try that in my next log.

Stock file attached.

Have you tried reverting your Clutch Fuel Cutoff table changes to stock to see if the rev hang goes away?

I have not. I absolutely will though.