E92 M3 Exhaust Dilemma

[cooll_m3]

Hello everyone

Around March I bought a 2011 E92 M3 and immediately ordered a full catless exhaust from Bomiz. I got the full stainless steel axel-back and catless race xpipe which is nothing more than a pipe with two resonators. It just arrived a few weeks ago and I installed it myself and it sounded good, really good, as a side, even as a huge car myself this thing was loud and made me a little uneasy about daily driving (people may call me a wimp or a fraud but that's just me).

The noise was a little over the top, but it sounded so good I got around it in no time; however, the smell was unreal. Any time the car was on it wreaked of exhaust fumes. A couple of days ago I finally threw in the towel and slapped the old xpipe and cats back on because it got to the point where I wasn't enjoying driving the car anymore. I kept the xpipe and everything for a couple of years down the road when it may become a track or weekend car and I can withstand the smell in short bursts.

I still have the straight piped axel-back system on and it doesn't smell anymore, but that sweet high-pitched V8 scream is gone and now I am left with what sounds like a c6 with an exhaust leak. I am wondering if there is a way I can get that top-end scream back without all the fumes or if that's just the price you pay for such a noise. I have looked at buying two 400 or 200 CEL cats and having them welded into the xpipe but I have been seeing mixed stories about this solution. If anyone has any suggestions it would be greatly appreciated because that sound just can't be beat.

[F4rmost]

Originally Posted by cooll_m3

Hello everyone

Around March I bought a 2011 E92 M3 and immediately ordered a full catless exhaust from Bomiz. I got the full stainless steel axel-back and catless race xpipe which is nothing more than a pipe with two resonators. It just arrived a few weeks ago and I installed it myself and it sounded good, really good, as a side, even as a huge car myself this thing was loud and made me a little uneasy about daily driving (people may call me a wimp or a fraud but that's just me).

The noise was a little over the top, but it sounded so good I got around it in no time; however, the smell was unreal. Any time the car was on it wreaked of exhaust fumes. A couple of days ago I finally threw in the towel and slapped the old xpipe and cats back on because it got to the point where I wasn't enjoying driving the car anymore. I kept the xpipe and everything for a couple of years down the road when it may become a track or weekend car and I can withstand the smell in short bursts.

I still have the straight piped axel-back system on and it doesn't smell anymore, but that sweet high-pitched V8 scream is gone and now I am left with what sounds like a c6 with an exhaust leak. I am wondering if there is a way I can get that top-end scream back without all the fumes or if that's just the price you pay for such a noise. I have looked at buying two 400 or 200 CEL cats and having them welded into the xpipe but I have been seeing mixed stories about this solution. If anyone has any suggestions it would be greatly appreciated because that sound just can't be beat.

I currently have a catless x pipe on my E92 with the factory rear section for now and don't notice the smell at all. I've had cammed corvettes etc without cats as well and the only time you ever really notice the smell in the car is sitting at a stoplight with the windows open or with the recirc off for A/C.

From experience, I have found the most common cause for smelling the exhaust fumes in the car is an exhaust leak. Replace those 2 graphite donuts at the front and really make sure the exhaust is sealed. I usually get under there while the car is running and carefully put my hand around all of the joints. Also, most of the time I retorque after driving for a little while to verify stuff is tight.

You can verify you're not running rich on top of it.

Worst case, you can get some high flow cats welded in, but that will mute some of the sound. Not all of it, but definitely some of it. It will definitely help with the smell though.

Best of luck.

[Reddevils7]

Op, are you talking about the smell from the outside or inside of the car. I also have a full catless x pipe with factory back box. I can only smell it from the outside or if my windows are both down and I'm sitting at a red light then I might get a whiff. Absolutely no smell should be coming if you're inside with the windows up. If so then I agree with the above that you likely have an exhaust leak as the smell should only be coming from the exhaust tips

Some people are more or less sensitive to the smell. It's my first car that's catless and I smelled it immediately when I picked the car up. With time I got used to it

[MShift]

I have the same issue, it seems like my car is way stinkier than any other catless M3's I've been in. If I just hang around my car while its idling my clothes will smell like gas immediately. Same thing happens if I drive at low speeds with the windows down. I tried checking idle AFR and it was hanging around 14.8 which I think its normal? Not sure what else it could be.