PID TRQTRANS, good bad or ugly?

[bobfo]

THe PID "Delivered Torque" (GM.TRQTRANS)

1. Does any one know what is used to measure it and how accurate is it?

2. Does it have a max?

3. Is it usefull for for judging how good a mod works?

4. Has anyone logged this PID on a dyno run and compared the results?


Thanks

[daveb]

I am also interested in this. I have been measuring these values which appear to be half what I would expect.

The max I see is 300 Nm on a car with 300 rwkw. The FW KW which is based on engine torque does not get above 200KW.

Has anyone else seen this?

[bobfo]

I don't think you are looking at the same PID I am. What PID's are you looking at?

I know the "POWER_RW" PID is a CALC PID and it would be low because it does not account for any aero drag. It is a calculation based on acceleration and mass.

[Blacky]

The CALC.POWER_RW will NEVER be accurate (except by chance) on a dyno. It measures acceleration and, from a known vehicle mass, can calculate force and then power. A dyno does not simulate (nor even attempt to) the vehicle's correct mass/acceleration.

Regards
Paul

[Blacky]

THe PID "Delivered Torque" (GM.TRQTRANS)

1. Does any one know what is used to measure it and how accurate is it?

That PID measures the calculated engine torque minus the torque loss from spark retard.
The torque loss from spark retard is determined by the calibration {B1902}.
The calculated engine torque is determined by the PCM from airflow, rpm and internal torque tables.

It appears that GM calibrated (or computer modelled/estimated) the torque output of the engine under various air flows, fuel ratios and rpms and stored those torque values into a table in the PCM. The PCM simply looks up the torque values in those tables based on the current airflow, fuel ratio and rpm and reports the "calculated/estimated" torque after filtering, smoothing, adjusting for spark retard etc.

Once you have modified your engine, the PCM's ability to accurately report the engine's torque output is compromised*. And therefor the value of that PID is also compromised.

*Unless you recalibrate those internal torque tables - but to do that you'd need an engine dyno. Which defeats the purpose of having an accurate PCM calculated torque value - which does not and can not exist.


2. Does it have a max?

Only in so far as the PCMs internal calculations have a max.


3. Is it usefull for for judging how good a mod works?

In my opinion, no (but I am not a tuner).


4. Has anyone logged this PID on a dyno run and compared the results?
Thanks

Not that I know of.

Regards
Paul

[GMPX]

I've heard this PID can relplace a WBO2 :lol: :lol: :lol: :lol:

[Blacky]

I've heard this PID can relplace a WBO2 :lol: :lol: :lol: :lol:

And I've heard you don't need a dyno either 8) 8)

[daveb]

BOBFO - I have been measuring the delivered engine torque and the trans torque. BTW the flywheel power uses the delvered engine torque.

Blacky - I thought there was a torque sensor measuring turning force on the drive shaft. Is this not the case? Since I have an auto torque values effect shifts and I have been keen to understand what the PCM thinks the torque is as desired shift times and trans pressure is calibrated using torque values.

I do admit it is pretty good as I have programmed the VSS changes how I like, but I do not understand when the torque values are used to determine shifts (ie D1108-D1110 & D0701-D0703).

Thanks,

[Brains]

Will you guys quit picking on John Rovner, he's smarter than all of us put together you know.... :lol:

[Dirk Diggler]

I've heard this PID can relplace a WBO2 :lol: :lol: :lol: :lol:


And I've heard you don't need a dyno either :cool: :cool:


You guys are too much. :wink: :wink: :wink: :wink:

[Blacky]

BOBFO - I have been measuring the delivered engine torque and the trans torque. BTW the flywheel power uses the delvered engine torque.

Blacky - I thought there was a torque sensor measuring turning force on the drive shaft. Is this not the case? Since I have an auto torque values effect shifts and I have been keen to understand what the PCM thinks the torque is as desired shift times and trans pressure is calibrated using torque values.

I do admit it is pretty good as I have programmed the VSS changes how I like, but I do not understand when the torque values are used to determine shifts (ie D1108-D1110 & D0701-D0703).

Thanks,

As far as I know, there is no torque sensor in the LS1 powertrain, well not one that is used by the PCM. If anyone knows differently please correct me.

All the torque PID values are calculated from other sensors and preset calibrations.
The shift times can be controlled by changing the transmission line pressure. The pressure (and therefor the shift times) can be calibrated based on the PCM's estimated torque delivery to the transmission.

Some (not all) PCMs are configured to adapt the line pressure (D0701-D0703) based on the desired shift times (D1108-D1110).

You can see the learned adapt-shift values in the EFIlive Scan Tool.
Menu: LS1/LS6->Auto transmission adaptive shift cells.

Even if the delivered torque values are not calculated 100% accurately, the PCM (if configured to) may "learn" the correct pressure to use to obtain the desired shift times.

Regards
Paul

[daveb]

thanks I'll try that.

DAVE