Auto Transmission torque reference

[LSChev]

Hey all,

I have been working with a couple of the new 8 speed transmissions lately. One for a 2015 Denali and one for a 2015 Escalade. Both have TVS2300s on them.

The DD tables are represented in throttle% vs. VSS and are reporting in axle torque. From my understanding, the ecu references this table to see how much "axle torque" is being commanded. Once it has a number I'm guessing it must have some sort of transmission table that it looks at to see what gear should be requested. for example:

Cruising in 6th on the highway (1:1) requesting 400 ftlbs at 2500 rpm. If I was to then request 800 ftlbs (but the engines peak torque for 2500rpms is 600) it should then look at the transmission table and know that it can make the required 800 by downshifting to 5th? Or if that wasn't enough, maybe 4th? This would be handy since I have noticed that these motors don't need to be spun to redline all the time to make good power.

Maybe there is something like this already in place? Any help finding it would be greatly appreciated.

[Higgs Boson]

The engine makes torque, the Driver Demand table tells the ECM how much it needs to open the throttle vs pedal to make the requested torque vs pedal.

The transmission shifts based on the shift tables....MPH vs throttle based.

The Driver Demand table went to axle torque for some applications in 2015, I think all of the 2014s I saw were engine torque in kilowatts.

[LSChev]

Hmm,

Well that's where the problem is then! I'm assuming the ECM and TCM must communicate. Why wouldn't they have the transmission work off of torque as well? Pretty easy to calculate since the tcm knows the mechanical advantage each gear has to offer.

Do you know if the throttle% that the tcm references for shift points is the pedal average or actual throttle blade %?

[jtrosky]

I spent a lot of time logging to figure out that exact queston (whether shift tables used pedal average or throttle position) - in my case (6T70 transmission, T43 controller), they used pedal average.

[LSChev]

I spent a lot of time logging to figure out that exact queston (whether shift tables used pedal average or throttle position) - in my case (6T70 transmission, T43 controller), they used pedal average.

Thank you, I will do some logging on the 8 speed and see if I can figure out if it is the same or not. I will let you know what I find!

[Ben Charles]

Main thing I look at is pedal position vs ETC desired position

[Higgs Boson]

Hmm,

Well that's where the problem is then! I'm assuming the ECM and TCM must communicate. Why wouldn't they have the transmission work off of torque as well? Pretty easy to calculate since the tcm knows the mechanical advantage each gear has to offer.

Do you know if the throttle% that the tcm references for shift points is the pedal average or actual throttle blade %?

It uses requested torque to determine the shift pressure, speed, characteristics.

It does use pedal position as mentioned above.