Popping from exhaust at wot

Crimson6.2L · April 2, 2020

I installed a set of speed engineering long tubes on my 17 6.2L with no cats and had it retuned on the dyno about 2 weeks ago. It already had been tuned on e85 with a afe intake and mbrp catback. Ever since the long tubes and even after the retune it pops. I know popping when it shifts is somewhat normal but if I go wot from a roll it’ll crackle and pop before it shifts. What would cause this?

Edited April 2, 2020 by Crimson6.2L

CamGTP · April 2, 2020

Here is my guess.

When you do a power downshift or when the engine does any shift for that matter, the computer will pull timing and a lot of it. If this part of the calibration is mostly unchanged the computer can re-tard up to -25 degrees of timing to help complete the shift.

So you could be rolling along at 25-30 degrees BTDC and when you slam the throttle down it's now turned into -20 degrees BTDC or what it really is is now 20 degrees ATDC.

I could possibly see that the pops/crackles are from this because the spark is happening when the air/fuel mixture is no longer in the cylinder and partly in the exhaust. It's possible that some of the pop/crackle could be toned down if you lessened the amount of timing pull taking place but you can't do too much because to keep the transmission and torque mngt happy there still needs to be a good amount of ignition advanced taken away.