LT4 Bigger pulley tuning

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.

Not familiar with the LT4 ecu at all, is this your primary driver demand map? This is in Nm, right?

I can't read the files, but it seems to be a protective torque limiter, usually found on automatics but may be for the clutch or input shaft on a manual. The loading is different in different gears and inclines, it may be only just hitting it when the loading is sufficient to slow down the acc'n inertial losses within the engine.

About all i can suggest is having a search for torque limiters for the ECU you're using.

Hi Michael, Gord, thanks a lot for your replies. I invested more than 100 hours working with the DRVDMD tables and all the other tables and parameters that seems to be related to torque limiters, I took the car to the Dyno three o four times, testing diffents configs. My last hope is that somebody in the blog has deep experience with LT4 engines and can help me. Thanks both again for you help.