Exhaust vibration

[Eyeman]

I picked up my recently modded One including catless downpipes. It ran great then I came up to my first stop and immediately noticed a weird rumbling/vibration. At first I thought maybe my pipes were rubbing somewhere and I'm still not positive that they aren't. I researched the subject and figured I'd start a new topic.

From my reading it seems N54's are a little prone to vibrating at idle and a little less at 1500-2000 or so rpm. Some completely stock owners on the E90 site have complained about this. Maybe they are more susceptible due to their dual exhausts with better flow.

Common sense would be that if we make our exhausts flow better that everything would feel smoother in the car but actually this increased exhaust velocity does create extra energy which is probably what causes the rumble.

Just adding an axleback I noticed I could slightly "feel" the exhaust, but it was in no way bothersome. When I added my dps, I now have a rumble. When I come towards a stop (autotrans) my car is still smooth and then when completely stopped the noise level will distinctly increase maybe 20% and I'll pick up a little more vibration/rumble. It's not bad but very distinct. I can cut on the AC and increase the effect. It's also increased when the car is stopped with the front of the car inclined (which makes me still wonder if my dps are rubbing something). As soon as I slightly change the rpm the rumble goes away. After reading about others complaining at 1500-2000 I now notice that I have that also but it's not bothersome at all to me.

It slightly brings up the issue of whether the flex portion of the stock dps actually servers to help prevent this. Some have associated it with oil changes, which I also had done when I had the dps installed.

Either way, I felt this was an issue that I hadn't read much about on this site so I brought it up. Of course comments from the experts are welcome and maybe I'll find out my issue was simple and fixable. Either way I'd still want dps for the hp gains that I plan. However, I might have waited to install the dps when I was ready for a tune if I had known that I'd pick up this rumble.

Comments?

[Nick135i]

You have exactly described what I have experienced in my car too.

I have recently installed a catless stainless steel exhaust (full). The car has stock down pipes. At Idle there is a significant vibration - and interestingly as you described - it is worse on an incline. My exhaust is almost stock noise/vibration levels between 1500 and 2000 RPM - below 1500 it has a vibration/rattle, Above 2000 it has more of a boom. I am disapointed in the sound of the exaust - because it never sounds sweet. However the performance is definitely there. Also as you describe turning the A/C on or off can change the vibration or make it go away for a short time.

It is interesting that 2 different approaches to the exhaust can have a similar effect. It sounds like a more fundamental issue.

Any one else experience this ?

[Eyeman]

I guess it's just you and me Nick..lol. Actually I'd bet many of the high performance guys this effect, but they expect it and don't even think twice about it.

It's mainly just an issue anyone modding should consider. Your car will be less civilized as you mod, performance can effect smoothness. I'm getting more accustomed to my noise now and barely notice it after only having it a few weeks now.

[Raflekt]

What exhaust brand?

I have my CP e catless dp s and I dont feel any difference in noise or more rumble it only feels...... Fasterrrrr jajajaja

Thats the problem with a 3 in complete DPs

[Eyeman]

I do have the supposed biggest dps, the AR catless ones, ceramic coated too, with the MadDad axleback, stock midpipes, no tune. But since I've read about some 335 owners complaining and having stock exhausts and this increased rumbling, I doubt it can be specifically related to any single part. But increased exhaust velocity does seem to make it more likely.

[Mega Man]

Is it exhaust rattle or valve reset?

[Jaguar66]

!

[My135]

Vibration at idle or only vibrated in the prescribed RPM range during acceleration?

[ILMOSTRO]

I have a Dinan full stainless steel exhaust with black tips. There is a little rattle at low rpms when I'm not on full throttle. Nothing harsh. It's interesting to read that people have felt there car is faster after modding their exhaust because I haven't felt any more power. Probably psychologically associated with the new sound. Sounds great though.

[LemansE82]

Maybe the mid pips might be too close to the underbrace?
Hear any clanking when you hit hard bumps?

[rcracer_tx]

Catless downpipes adds to the vibration from the exhaust. That is what you are feeling most likely...

[Eyeman]

I'm pretty sure RobMason is onto it. I'm 98% positive that none of my exhaust rubs.

The "droning" at idle is the easiest to notice and is the only part that might bother some people (to me it's no big deal, just wanted others to know about this phenomenon). Usually it goes down or away if I shift to neutral or turn off the AC, sometimes it doesn't.

In my mind, I didn't notice my intake, but for sure an axleback after the intake gave me more HP. Downpipes a similar addition. Each made the car louder though so it may just be a mental thing. I may never dyno my car, it really doesn't matter to me, so I guess for me it's fine if I just think it's faster..lol.

[MrBimmer]

Originally Posted by BR3CK

I have a Dinan full stainless steel exhaust with black tips. There is a little rattle at low rpms when I'm not on full throttle. Nothing harsh. It's interesting to read that people have felt there car is faster after modding their exhaust because I haven't felt any more power. Probably psychologically associated with the new sound. Sounds great though.

Do you have a video showcasing the sound? i would love to hear it!

[Eyeman]

I figured I had better update this post.

My exhaust "droning" at idle has definitely improved. I guess it's possible that I've just gotten accustomed to it but it's probably more likely that something else has gradually occurred. I'm guessing the exhaust getting a good inside carbon might have done it. ECU adaptation to the new exhaust might have done it. Hotter weather? More mileage after the oil change? Anyways, it's barely noticeable and often not even there now.

[rotelly]

I have the same problem. CP-E catted Exhaust/DP

[JohnL135I]

Check your downpipes and ensure they are not touching the sub frame. What will happen is when your at a light one of the downpipes might be contacting the sub frame, just slightly. When you accelerate the motor torques away from the sub-frame so you won't have any vibration.

[rotelly]

I had it up in the air yesterday and the downpipes look fine. It happens when I am just idling.

[jeremyc74]

I noticed a slight increase in highway vibration after installing catless DPs. The factory pipes have several expansion bellows on them that will absorb some vibration, and the aftermarket pipes don't have them. I suspect that's what I'm feeling. My friend who runs an exhaust shop was concerned about it when we were putting them on the car, and he was right.

Now, on my car (which is a manual) the only time I noticed it was on the highway, and right after I had changed them. It's not bad at all, but there was a noticable increase. On an automatic car the idle is probably a little lower when you're sitting at a stoplight in gear, so maybe that's the difference?

Does it go away when you go to neutral?

[rotelly]

I'll check, the chatter caused by the vibration is so bad i am thinking about going back to stock.

[Eyeman]

Give it some time, mine is much better now. I sort of doubt the stock downpipe flex section is related since some 3's get this just from opening up the exhaust from the dp's back. I think it's the exhaust velocity itself causing a droning of sorts. I still get some weird noises at times but mostly I just get great sounds and great performance now that my exhaust is broken in through multiple heat cycles, etc.

[rotelly]

I had my local shop replace the clamp and the noise went away.

[1013mm]

yep my car rumbles at idle, stock too. at first i thought it was hpfp failure, but it just what the car does... my 328i doesnt do it so i guess it has to do with the turbos somehow...