Background:

Soon after I purchased my car (2003 Z06) I did the zip-tie mod and though I didn't notice any SOTP improvement I did however notice that my exhaust pipes were getting very sooty. That to me indicated that I was running richer, which made sense i.e. more air in the car compensates by adding more fuel.

After about 1500 miles I stopped by 21MC for a tune, thermostat, and minor exhaust. I also replaced the factory paper filter with a K&N. The initial dyno revealed that my car was running very rich and my initial numbers were 337.9rwhp and 324.6rwtq. After tuning my numbers improved to 369.7rwhp and 350.0rwtq. The real benefits were improved gas mileage and clean "soot free" tail pipes. I went a little further with mods by replacing the OEM airbridge with the Halltech Stinger airbridge so that I would have a place to install my nitrous nozzle but that produced no noticeable effect on the car.

Very recently I replaced the zip-tie modded air box with the Halltech Stinger filter however, once again my exhaust pipes are very sooty.

So now for the question:

Is it possible that somehow my custom tune is being/has been overridden by some other computer tables within the car's ECM causing my car to add even more fuel due to the increase in airflow with the Halltech filter?

 

The PCM will have to readjust for the additional airflow, if it can. The PCM can only adjust so far, and will have to readjust everytime the battery's removed for an extended time. I would think the flow difference wouldn't be great enough to require a re-tune. Drive it for 100 or so miles and see if the soot clears up.

 

adaptive strategy will eventually learn out the trims from the subtle airflow changes from the additional mods, but that all goes out the window when you go open loop/WOT (Power enrichment). At minimum, it would be worth it to throw a Wide band on it to see where the WOT AFR is. Shoot for a PE AFR of 13:1 on your stock n/a LS6 motor.

robert / Gen 3 MS

 

Thanks for the input guys.

 

Isn't power enrichment dependant on throttle position and RPM? It begins, for hot operation, at 45% of full throttle between 0 and 1400 RPM and then only 23% at 1600 to 2400 and then 19% from there to redline. WOT is not required to hit the power enrichment curves as I understand it......but I'm still learning

 

The Stinger filter probably flows more - same situation as with the original zip tie mod. Mods that increase flow (intake and exhaust) will cause the car to run lean (as sensed by the 02 sensors). The PCM adapts by adjusting the longterm fuel trims (LTFT) to a positive number to increase fueling at part throttle.

The problem with this is at WOT, any positive LTFT's get added to the power enrichment calculation - which is what controls your WOT mixture. As the cars are usually on the rich side from the factory here, the added fueling over compensates for the mods, and the car runs even richer than stock.

Your tuner can fix this, but as you have seen, each mod really likes to be optimized. On the plus side, you should make even more power

 

Yep, this appears to be the case. I guess I didn't expect the Stinger filter to flow that much more, but all evidence indicates that it in fact does.

I'll be doing major mods (LTH with H/C or Maggie) real soon that will require a custom tune so it will all come together then.

Thanks guys