Had my car tuned this past summer for my current setup. I noticed after all said and done , I took it on the highway a few times and got on it and it was backfiring. Was told it was normal and as long as my a/f looked fine witch it did then its fine.

Well lately I've been kinda questioning it. Its colder out and my car was tuned in the summer and from what I understand the colder the weather the higher the chance of this happening becomes because the a/f ratio leans out from having denser air. (at least i think).

Anyhow , the question is how normal is it and is it bad? Any time I get on it usually 1-2 backfires around 8-9k before I shift almost every shift and if im at 8-9k or so and just let my car decelerate while in gear it backfires 1-3 times as its decelerating if i put it in neutral and just let it decelerate, nothing happens.

Here's my setup if it helps
1220sl comptech s/c 10 psi pulley installed
5zigen header
70mm invidia tp
70mm invidia single exhuast
1000cc injectors
tuned on a aem v.2

 

Sounds like you are hitting boost cut, in the winter the denser air helps increase the boost on a supercharged car. I would pull up your map and see what PSI you are running and check where the boost cut was entered.

Good luck

 

[QUOTE=dsddcd,Dec 25 2010, 11:46 AM] Sounds like you are hitting boost cut, in the winter the denser air helps increase the boost on a supercharged car.

 

Backfires are usually from running rich not lean in between shifts or when letting off the gas.
What afr's are you seeing?

 

Technically its called after fire