Exhaust crackle and pop through flash (Unitronic) ?

**IceSilverS4** · 12-28-2015 08:20 AM

I run a Unitronic flash, but the question can be applicable to all other flash companies.

What makes a car exhaust crackle and pop where decelerating without pressing in the gas ?
Would this be possible on the S4 with a reflash ?

Perfect scenario would be to have this feature in dynamic mode only.

**GRUMPY-S4** · 12-28-2015 09:23 AM

On an FI car thats normally happens when the car is running rich and fuel is left upon decelerating

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**IceSilverS4** · 12-28-2015 09:56 AM

I wondered if there is a way to tune this safely, since most newer performance car does it.

**tgsweat** · 12-28-2015 09:01 PM

My car does it with my awe exhaust

**Loe** · 12-29-2015 03:40 AM

the snap-crackle-pop upon throttle overrun is induced by a controlled "misfire" upon letting off the gas where the fuel injectors are still cycling without ignition spark. My E90 335i did this upon decel at times (BMW's own performance power ECU features this overrun as well) and you can actually induce it by slightly pressing on the gas when you are decelerating in gear (and I mean slighty pressing as to not accelerate). My E90 M3's EVOLVE tune featured this. Long term effect is more than likely minimal on metallic cats, otherwise certain cars would not do this from the factory. However, not sure if our cats are ceramic or metallic? With that being said, anything is entirely possible