BACKFIRE WHEN I SHIFT IN HIGH RPMs??

[Timshadi]

Hey guys, is it normal to hear a loud pop when I shift gears at high rpms???? I do back fire quite a bit when I rev the engine up to high rpms, and it rumbles when my car isn't warmed up, but I just noticed the pop when I shift. I know im running rich, but is there anything I could do to fix this??
mods are COBB SRI, Forge BPV(blue spring) , Stock downpipe, testpipe, and deleted both resonators, stock plugs and no tune. its a 2008 ms3. Any insite would be great!

 

[Ninkumpoop]

From my knowledge, turbo cars run slightly rich during boost to help keep the combustion chambers cooler. Deleting cats would promote backfiring since there wouldn't be anything there to clean up the excess, unburnt fuel. Not sure what resonator deleting would do for backfiring. Shorter exhaust piping will also promote backfires since exhaust gases cool while passing through the piping. I'm currently running both cats deleted, single resonator, and one muffler and I do backfire once in a while. I've noticed that after I get on it hard a few times, I tend to backfire regularly. That's not to say that I have ridiculously loud ones every time, but it just happens more often after I've built up my exhaust temp.

 

[bluwheelbeauty]

Also if your running VTA on your forge creates it as well.

 

[Spiced MSP]

i agree, when I got my catless exhaust I would get an occasional backfire and it only got worse when I went VTA. It gets annoying sometimes, other times it is funny to watch the reactions on everyone's face when I pass by because it scared the crap out of them. When driving normally and downshifting, I get a few small pops and a low rumble. When boosting sometimes or just accelerating quickly, I get a loud backfire. Gotta love the echo under bridges and in tunnels. I try to stay away from driving beside cops because I don't want to experience that one time my car has a loud backfire and I get pulled over for being catless or something crazy. Maybe a tune will help tone it down. Thanks to the pig rich air/fuel ratio

 

[714ms3]

It is due to not having the resonators. I have the identical setup to you OP, and it only started when I removed the resonators.

 

[Saskatchewan17]

I backfire and I have no resos and both cats still in place. I've always ran recirc. I've noticed it more in the cold weather... after getting on it for the first time (dipping a bit into boost, shifting at around 3,500 RPM) after the car is warmed up I'll get some nasty backfires sometimes.

 

[liquidflem]

This is totally normal for turbocharged cars. My car does it often when shifting at around 5.5k-5.8k. I saw a Volvo sedan (T6) the other day that gunned it hard at a light and it backfired when it shifted.

 

[SPEED DEMON]

It has to do with no cats/resonators. I have no cats, deleted the rear resonator and the "muffler" and now I get a backfire and flames at wot between shifts.

 

[MSMS3]

At WOT don't lift and it won't backfire. LOL.

Seriously, I don't recommend flat shifting, but it is the sudden let up and press back down on the accelerator pedal during the shift that contributes to making a pig rich AFR worse due to the temporary change in engine load, throttle position and fuel demands during the shift.

If you are catless and have no resos, the occasional backfire comes with the territory, IMHO. With a catless exhaust system, I do get it too, except when I flat shift -- something which I do not recommend except in competition.

 

[liquidflem]

Totally normal, who here watches WRC

 

[massiespeed3]

im running kinda the same set up just a cpe nano insted of cobb i have the stock cats no resonators and i pop all the time i recirc my forged bov with blue spring 2 shims. even cruising at 50-60 mph if i push the clutch in my car will pop laud as hell. first time it did it i had the radio on kinda laud and it sounded like a blew a tire

 

[djthom]

keep that forge lubed at each oil change

 

[RC08MS3]

pfffttt, backfire? thats it? i get about a 3 foot flame

 

[SPEED DEMON]

pfffttt, backfire? Thats it? I get about a 3 foot flame

+1

 

[bigdaddy]

this does happen to me occasionally, and I personally think it sounds pretty sweet, although of course, it is a backfire.

 

[justanothermp5]

normal, and sounds uber JDM

 

[hectik1]

Since it has been colder mine pops and backfires when downshifting. Reminds me of my old Evo, without the flames!

 

[shpankey]

i have one cat deleted. i noticed with the cold weather it started doing it for the first time. used to not do it. like this last summer, i had the cat gone then too but it would rarely if ever backfire. but with the crazy cold temps it has started to.

 

[liquidflem]

Mine has started to pop during high RPM shifts now that it's cold too, everytime now. It's around 35 or so here during the day.