First951

Hello everyone, I am getting alot of popping/backfire when getting off the gas after installing bursch testpipe and 3" sfr exhaust. I have guru 18psi chips, but only running 15psi because i am trying to find a boost leak.
Thanks

awilson40

Its normal if its not excessive. If its a lot then you may be a bit rich.

hosrom_951

Just like Awilson40 said. Since you have a test pipe, the fuel droplets are popping in the exhaust. So, it is normal.

First951

Thanks Guys

toddk911

Yea, when I first went to the 18psi chips mine did it also, then seemed to stop.

toddk911

For some reason, if it does do it, it is only right after shifting when at redline and letting off the gas.

Tom M'Guinn

My car does the same. The richer it is, the more it will do it. If you are running 15psi boost, but using enough gas for 18psi, then you are probably richer than the ol' Guru intended.

Laust Pedersen

Same here, so I am just calling it a “charming feature” and as I recall, it does not occur if you fully let off the throttle (shutting off the injectors) on gearshifts. I have noticed on my O2 sensor that just touching the throttle on overrun will make it go rich and some popping occur.

My case may be a little worse since I some time ago had to grind out the last (cracked) brick in the cat, leaving to front brick intact, which I believe does the reduction of NOx to N2 and O2 to react with the excess HC. Yes, my backend gets those ugly black spots too, requiring more washing than I like.

Laust

turbite

you could check your TPS. (search for how to do this)
It should shut off the fuel entirely when you let all the way off.

Danno

"you could check your TPS. (search for how to do this)
It should shut off the fuel entirely when you let all the way off."

Yup, it's that fraction of a second between when you let off the gas and when the TPS clicks to signal the DME to drop into the idle-maps and cut the fuel that you get excess fuel that causes the pops. This is actually due to the closed throttle shutting off air but the AFM at over 6-feet away, still has air moving past it. So no air goes into the engine, but the DME still sees lots of air flowing past it. Thus it still injects fuel for air that's not actually going into the engine. Thus the extra fuel and the popping.