Odd STFT issue - Random -10%

[bdevlin]

Hey everyone,

I hope you can help point me in the right direction on where to start with trying to isolate this issue.

The issue is I get these random high negative STFT values (LTFT's have been disabled completely).

I can crank the car, bring it to operating temperature log a 10 - 15 minute drive and the values are ALL within -2 to -4%. Then without making ANY changes to the MAF Frequency table, turn the car off, turn it back on, and right away I get this consistent large negative values and it continues even past idle.

This car was tuned twice before, and I'm just now trying to learn how to make adjustments myself. But it's hard when without making changes I see so random of trims that I can't adjust accordingly. So far I've not made any changes to the tune file (except for changing my rear gear size).

This occurs with both the MAF only tune file and the current tune file in the car.


It's a 2015 Camaro SS

Mods:
Texas Speed 231/236 cam
Long Tube Headers
Cold Air Intake
GM NPP Exhaust
Electric Cutouts (Cutouts were closed during the test)


Thank you ahead of time, I truly appreciate it.

[Higgs Boson]

evap purge probably needs to be filtered out of your log

[bdevlin]

evap purge probably needs to be filtered out of your log

Thank you for the reply. I'm not able to test this at the moment as I'm not near my computer. I do have a couple of follow up questions.

Is there a VCM control I can use to temporarily disable EVAP from purging for testing?

If I wanted to filter out purge from my log, would I use the Commanded EVAP Purge PID and filter based on that?

I can see how this would affect the trims for sure, so I'm glad you brought this up.

[Higgs Boson]

Thank you for the reply. I'm not able to test this at the moment as I'm not near my computer. I do have a couple of follow up questions.

Is there a VCM control I can use to temporarily disable EVAP from purging for testing?

If I wanted to filter out purge from my log, would I use the Commanded EVAP Purge PID and filter based on that?

I can see how this would affect the trims for sure, so I'm glad you brought this up.

used to be you could filter out the evap airflow mode but I am not sure on GenV stuff

[bdevlin]

After more searching, I've found the issue.

https://www.hptuners.com/forum/showt...h-after-Flash/

It appears to be related to the injector tip temp table. A update was released, zeroing out that table should clear the issue (will test it tomorrow).

[Higgs Boson]

That was a GenIV issue, I haven't had that with any GenV cars. It's also a rich after flash issue, not a rich after every start.

[GHuggins]

Well his is a 4th gen calibration and if it has large injectors the injector tip temp table not being dialed in will cause rich after start issues too as the ecm always defaults to the high restart values for quick restarts - if you let it sit for 30ish minutes it cranks on the 60ish Celsius temp values... If you don't have injectors then look at injection timing for the cam as it is directly temp dependent...

[Higgs Boson]

Well his is a 4th gen calibration and if it has large injectors the injector tip temp table not being dialed in will cause rich after start issues too as the ecm always defaults to the high restart values for quick restarts - if you let it sit for 30ish minutes it cranks on the 60ish Celsius temp values... If you don't have injectors then look at injection timing for the cam as it is directly temp dependent...

woops, maybe this thread should be moved to the correct forum....

[GHuggins]

woops, maybe this thread should be moved to the correct forum....

Yeah, I was scratching my head reading the problem too until I opened the tune Only time I've ever seen DI motors go richer when hot was when the injection timing was really screwed up or when the idle tq controls were going bonkers throwing timing way off... Otherwise never happens...