under pressure

iTrader: (13)

My LS6 powered project has 2.5" dual exhaust with a magnaflow bullet and a cheap single chamber muffler on each side. The sound was just too loud in the cab (exhaust exits in front of the axles) so I added a pair of 90 degree turndowns to quiet the sound. It seemed to do the trick for what I wanted but now my air fuel ratio is up over 15:1 when cruising with a lean miss and stumble. I have a wide band sensor in each side so I can verify the lean condition. I can imagine an exhaust improvement creating a lean tune condition, but why would turndowns do this? I can retune the program but I don't get why the lean out has happened. Would adding backpressure cause this condition?

HoLLo

iTrader: (17)

No way turndowns did that. Something else happened.

And backpressure is term misused, really what you need to think of is gas velocity.