Exhaust noise after install.. video included.

[FoFoJoe]

2001 Boxster, 2.7l manual 119k miles.

The exhaust system is all from TopSpeedAuto, with the headers, midpipes, and muffler.

*Protip* Never change the headers on your Boxster. Trust me, not worth the hassle. If I had a time machine I would stop myself from doing this. But I'm past that point now.

Anyways, so I recently "finished" (i.e. spent too much time and energy) my exhaust by installing TopSpeedAuto headers. The system has no cats. Feel free to bash me for ruining the environment.

The system is probably 5% louder than I would like but whatever, I'm stuck with it now but honestly its fun and rowdy when driving in the higher RPMs.

My only gripe is a new noise that I can best describe as a "clattering" or chugging almost at low RPM's from the drivers side header. Or that's where I think it's coming from atleast.

https://youtu.be/GsKi9Rp5-lw

The noise goes away over about 2.5k RPMs while driving. You can faintly hear it when accelerating from about the 2k and up range when driving. And the noise can't be heard (or is faint enough it blends into the ehxaust noise) when the car is on a lift and running.

It's most prominent when going from a stop -> first gear. First and reverse are both the same volume level for the noise.

My first thought was an exhaust leak, but on 2 different occasions we've had the car up on the lift listening and feeling for an exhaust leak and we can't find anything. The header bolts have been retorqued to factory spec twice now. We've removed and reinstalled each exhaust clamp, and I even installed the Torca Easyseal clamps to replace the factory midpipe clamps. The O2 sensors are tight as well. I also installed Car Chemistry baffles to reduce some of the raspy sound, and those are clamped where the Torca easyseals are located. After a good 2 hours of revving and listening with two other people helping, we couldn't find a leak anywhere. And again, the noise isn't present when the car is on the lift and revving.

I'm stumped, any insight on what's causing the noise?

[maytag]

Clue is that it's not there when on a lift.
I'm betting your header or mid pipe is hitting a cross member or sway bar. Mine did, before i got creative with heat and ratchet straps on the header. They're so cheaply made that they're "close to fitting" but not quite.

Sent from my SM-G970U using Tapatalk

[FoFoJoe]

Originally Posted by maytag

Clue is that it's not there when on a lift.
I'm betting your header or mid pipe is hitting a cross member or sway bar. Mine did, before i got creative with heat and ratchet straps on the header. They're so cheaply made that they're "close to fitting" but not quite.

Sent from my SM-G970U using Tapatalk

Now that you mention it, I did notice the mid pipe was touching one of the support arms. I was fixated on it being a leak, so I disregarded it. But I will definitely try that out. Did you basically bend the mid pipe?

I would probably pull the mid pipe before I mod it to avoid stressing the header bolts. 2 of the header bolts broke off and had to be drilled (not a fun day) so I don't want to risk the threads.

[FoFoJoe]

https://youtu.be/mO3-TtcMO7M

Here's a quick look at the rear end. The transmission mount arm and the midpipe are close, but there is a small gap. I'm thinking it could be the top bolt of the header-midpipe flange as well, since it's a tight fit up there.

[itsnotanova]

Has the front engine mount ever been replaced? The motor might be moving enough that the exhaust is rubbing.

[FoFoJoe]

Originally Posted by itsnotanova

Has the front engine mount ever been replaced? The motor might be moving enough that the exhaust is rubbing.

Yes, that was one of the first fixes I did when I got the car almost 3 years ago now. At the time there was a vibration when driving at about 3k RPM's.

The trans mounts were replaced as well about 1.5 years back when I did the clutch.

[FoFoJoe]

Here is a screenshot from the video showing the gap between the midpipe and transmission mount bracket on the drivers side. I will check out the top flange bolts between the header/midpipe next time I am under there as well, that was the only other tight clearance I can remember.

[FoFoJoe]

In revisiting my old posts, I realized I never posted my solution to this problem.

I had used the included gaskets with the headers I installed, not realizing they were basically crap compared to the proper OEM gaskets that are stamped sheet metal designed to fit the stock exhaust ports/channels. The noise was fixed by installing new OEM exhaust manifold gaskets, and besides some light raspiness when cold the exhaust sounds great when warmed up.

I'll post a startup and driving video here soon.

Lesson learned, use the right gasket the first time.