Odd 6L80E Behavoir

[Webbs]

I was doing some data logging at the track this weekend and I have some odd behavior that I can't seem to put my finger on. As you will see the run starts at Frame 737 and at frame 745 the car pulls 22.5 of timing ramps it back in and then pulls 24.5 degrees at frame 753. At the shifts I see the throttle position drop 40-50% and the timing drops to -2.5*. I expect the timing to dip due to the upshift torque management, but have not seen it drop throttle position before. Any ideas?

W~

[Rhino79]

It looks like you were spinning. What is your rev limit set at? Also what kind of shift times are you commanding at the higher load/rpm ranges?

[Webbs]

It looks like you were spinning. What is your rev limit set at? Also what kind of shift times are you commanding at the higher load/rpm ranges?

Rev limiter is at 7000 and the shift times in the higher load/rpm ranges are +/-.300. The part that messes me up is three weeks ago at the track with the same engine and trans tunes no issues?

[Rhino79]

The rev limiter is pulling the throttle closed it looks like. Has there been a gearing or tire height change? Whats the commanded shift rpm you want?

[Webbs]

I have attached a previous log file that was good accept for a lean spike at the beginning of the run due to fuel slosh.


I was shooting for shift rpms at:

1-2 6500
2-3 6900
3-4 6900

There have been no changes to the car other than a fresh tank of fuel.

W~

[Rhino79]

Hmmm, trans may be going away. Try lowering the wot shift mph by 3-4% to see if it effects it

[Webbs]

Hmmm, trans may be going away. Try lowering the wot shift mph by 3-4% to see if it effects it

Did it no change. What could cause the throttle to close? During all runs the pedal was at wot the whole time, but the log shows a reduction in tps%? Not sure what is going on in the background to cause this. Maybe the trans is on its way out.....

W~

[Rhino79]

You were hitting the rev limiter, and I bet the rev limiter in your ecm file is setup to limit via throttle.

[Webbs]

I'll check but the limiter is set at 7000 and the TPS drops at 6800ish. Unless this is a preemptive strike by the PCM? I have been doing a lot of reading and there are few people having this issue but nobody says what fixes it. Rhino79 thank you for the advice and ill give it another go

[Rhino79]

The rev limiter has a table for accel modifier that will act as a soft limiter at different accel rates. I usually 0 the accel mod out.