Anybody else have issues with exhaust coming into the interior under hard acceleration?

My '03 MCS has been doing this since I had the dealer install a MiniMadness catback (and pulley) last October; at the same time they did a warranty flywheel replacement. This is most noticeable going up hills, but I think that is due to the prolonged period of driving under load.

At first the exhaust leaked audibly, which the local Midas traced to a stripped clamp near the mufflers. With this replaced, they could find no other leaks, but the exhaust smell is still present under hard acceleration.

I just had it into the dealer yesterday for a detailing and to address this issue, and they came up with this explanation:

"No leaks in the system. Due to increased emissions from the modified engine, exhaust is coming in through the rear cabin vents under hard acceleration going up hills".

Sounds like a load of crappola to me. The vents they pointed to as the culprit are, as explained to me, there to ease closing of the tailgate when the doors and windows are rolled up (cabin is airtight), and are basically gravity/pressure activated flaps. As such, when going up a hill they flap open, allowing exhaust gases from the negative-pressure area at the rear of the car to come into the cabin.

Again, this condition is present on all grades, and I think that the dealer may be trying to feed me a line.

Any thoughts? I've had my car in to two different places six times now to fix this, and I'm getting really tired of it.

cheers

greg v.

 

when i pull my MCS out on a cold dry day, the vapors from the exhaust
will literally cloud up the rear window the first 5-10min of motoring.

therefore, it could be possible that is is coming from the rear of the car.

 

Yup, its the negative pressure area at the rear of the car that tends to keep things swirling around back there, hence why my Mini seems to get far dirtier in the back than anywhere else, including road silt & other debris.

That part of the explanation I'm not debating, its just the whole "flap" detail that has me wondering.

Let's put it this way; if everyone with a JCW style catback (which is what most aftermarket catbacks to be patterned after) had an issue with exhaust gases coming into the interior under hard hard & prolonged acceleration, then you'd think it would be a well-known & oft-discussed issue, but it doesn't seem to be.

So perhaps something else is going on....

greg v.

 

Does your exhaust tip extend beyond the lower bumper fascia? The gases generally rise and any leaks below the body will rise into the cabin.

It is very bad to be breathing your exhaust. This needs to be fixed.

 

Yup, the tips extend past the bumper by about 3/4".

gv

 

I just measured them, and the tips protrude about 1.25" from the top of the cutout, which is about 3/4" from the mean face of the bumper. However, the tips are angle cut, with the tops being out further than the bottoms.

I think the next step will be to tape up the two vents in the trunk and see if that prevents the exhaust from getting inside; if it does, then bingo. If not, back to the drawing board.

gv

 

Temporarily taped up the two vents in the trunk, and so far no exhaust smell....

So can I leave these vents taped up indefinitely? Anybody know exactly what they are for?

I'll do some disassembly over the weekend and see if I can eyeball any missing parts or deficiencies in the general area. The Mini had a quarter panel replaced at 1200km (before I owned it), so maybe there was something assembled incorrectly.

gv

 

My 03S used to have a smell with the stock exhaust of and on. Once I put a n aftermarket exhaust on it seemed to go away.