LT4 bigger pulley torque limits issues - Camaro 1968 (lot of work done). HELP!

[wdiegogarcia]

I installed a bigger pulley to an LT4 engine in a Camaro 1967.
I'm experiencing a kind of cut power between 5.200-5.500 RPM. It sounds and feels like some kind of limiter. The fails appears around these RPMs and then the engine works fine reaching the rev limiter without any problem.
The fail appears when I accelerate from 3rd gear to 4th gear and reaches the 5.500 RPM.
The fail doesn?t appears if I accelerate from 1st gear to 2nd gear and reaches the 5.500 RPMs.
Finally if I accelerate from 3rd gear to 4th gear in a descent the problem doesn't appears.
I worked a lot with different tunes, the attached one is the last one. There a couple of things that I saw in the logs but couldn?t solve:
1- PEAK ENGINE parameter reaches a maximum of 879 lb ft and no matter how much I increase the PEAK ENGINE Table it doesn't raise any more.
2- MAX ENGINE TORQUE reaches a maximum of 879 lb ft.
3- COMMANDED ENGINE TORQUE reaches a maximum of 879 lb ft.
4- ENGINE TORQUE is greater than PEAK TORQUE, MAX ENGINE TORQUE and COMMANDED ENGINE TORQUE
5- DRIVER DEMAND tables: you could see that there are some zones in the log where these parameters get closer. I raised the DRV DEMAND tables but didn't see any improvement.
6- MAX AIRFLOW tables: I increased it progressive and finally maximized.
7- MAF AIRFLOW table: I didn?t work yet in the partial throttle areas, because I want to solve first the problem in the WOT area. As you can see there are not lack or excessive fuel in the fail scope (5.200 to 5.500 RPM)
8- Virtual Torque Tables: I tried increasing it first 10%, 20% and finally 30% without any change.
9- Throttle body is not closing and the ECU is no removing advance in the problem area.
10- VOLUMETRIC EFFICIENCY AIRFLOW parameter reaches 512 g/s around 5.300 RPM and stay in this value constantly while MASS AIRFLOW (SAE) parameter continuous growing and reaching a max of 655 g/s.
11- I checked a hundred of times and never appear a DTC error.
If I use the OEM Tune the error disappears but obviously the engine performance, without any tuning, is worse than before adding the new pulley and shows a lot of lean areas.
Sorry for the long message, but I intended to bring all the info that I've.

[GHuggins]

Looks like your just WAY past the limits of your fuel system and it's saying Heck NO. Could just be because everything is so skewed and commanding super rich, but don't think your going to compensate for a 50% DC when it should be less than 25ish ideally.... It's cutting fuel when the problem is present. Those torque models and other limiter tables need to go back...

[wdiegogarcia]

Looks like your just WAY past the limits of your fuel system and it's saying Heck NO. Could just be because everything is so skewed and commanding super rich, but don't think your going to compensate for a 50% DC when it should be less than 8ish ideally.... It's cutting fuel when the problem is present. Those torque models and other limiter tables need to go back...

Hi, first of all thanks a lot for your help, I really appreciate it. I'm from Argentina and we're doing our first steps with 5th gen engines, so apologies if my questions are too rooky.

The config and scan files that I uploaded to the post are from the last test. I began working without doing any upgrade in the Driver Demand tables, peak torque, etc. and the problem always was there (around 5000-5500 rpm). Reading the The Tuning School Learning Material I began to rise those parameters to meet the
following criterias:
- Drv. Dem Axle Tq > CMD Axle Tq > Act AXLE Tq
- MAX ENG TQ > ENG TQ
- PEAK ENG TQ > MAX ENG TQ + 100
- (Est TQ + 75) < MAX Eng Tq

Was that a wrong path? I saw some improvements but I'm far away from the expected hp output and the failure is still there.

Regarding to fuel tuning, again sorry if I'm missing some basic concept due to my lack of experience, I worked using the MAF Tuning Process and in the issue area (5000-5500 rpm) I see a gap minor than 10% (please see screenshot attached) with an AFR around 12:1. Could you help me to understand which parameters are you looking at to identify that is too rich? How do you identify that the ECU is cutting fuel when the failure appears?

On the other hand, and maybe my English is not helping me to understand, what do you mean by "DC"?

Finally, If you could look at the first run to wot, I found something odd, the ECU delay the transition from closed loop to open loop up to near 5.500 rpm that is where the issue appears.

Thanks, and thanks again for your help.

VCM Scanner AFR.png

VCM Scanner Closed Loop.png

[kenand1988]

I would start over from the stock file. I'm not an expert but for your mods I think you have scaled the MAF incorrectly which is causing some of your fuel problems. You may be commanding 12.2 afr in the tune but when you are having the fuel problems your actual afr is in the 10s. I believe this is from cat over temp. The DC he is referring to is duty cycle, you have way surpassed what is considered safe for the injectors. Past 6-6.5ms is not ideal which is around 25% duty cycle and at times your pulse width even goes to 10 which is nuts.

If you want to stick with your current tune, turn COT off under temperature control and put the stock MAF curve back in it and go from there.

[ZincGT]

please log with these channels 202205 GM LT4 Camaro 1968 STEP9.hpt

[wdiegogarcia]

Thanks! I will take your advice and start from there and let you know the results. (the car is now at the upholstery guys, so I think that I'll can work in it next week). Thanks again for your help.

[wdiegogarcia]

Thanks! I will do a test with the current tune and these channels logs to get results from the current config and the I'll try with the Kernand1988 suggestion and log with these channels too. I'll back with the results next friday I hope. Thanks man.

[wdiegogarcia]

Hi guys, sorry for the delay but we were working in other parts of the car, and we couldn't tested until last friday. I follow your advices and now we get a driveable first version of tune. Thanks a lot for your help, was a really big difference for the tuning process know the 6.5ms injection time limit. There are some MAF Table areas that we need to work yet, some knock retard too but in general the car runs great. Just to give you more feedback, I'm attaching last tune and logs files for reference. Thanks again!!