I re-installed my OEM exhaust last week (still keeping my Joe-Z and will be installing them back on once I've bought some HFCs).

While I was looking at the JoeZ exhaust I just removed I noticed on the upper driver side header to exhaust flang seems like I was having an exhaust leak.

You can see below where the black stuff is compared to the passenger side. It would explain some of the exhaust smell I was getting from time to time and might also explain the lack of performance on my car recently.

Last time I dyno'd it made 370whp (without tune) but with Exhaust and Headers I was expecting higher numbers so this leak seems to be the culprit to some of my issues. It would have been hard to see while its on the car.



Driver Side:



Passenger Side:



Just to clear things out I'm still madly in love with my Joe-Z exhaust and don't plan on changing it anytime soon, I just need to install some HFCs.

 

Yup...that's a exhaust leak for sure. Problem solved with new gaskets. There is a power decrease and the exhaust leak looks pretty big, judging the pic of the flange.

 

Just for future reference...was the exhaust smell very prominent? How often would you notice the smell? After wide open throttle, regular driving, or once in awhile? Thanks in advance and I'm glad you caught this! Get it fixed! And re run your cousins e92 M3😉

 

forgot the thread, but someone posted some gaskets to use.did you use silicone along with a gasket? any CEL, and whats the reason for adding HFC?

 

Also how tight were the bolts and what condition were the gaskets

 

When I first installed the exhaust I had no smell, it only started after like a year or so. I figured it was the fumes coming out from the rear of the exhaust.

It wasn't always noticable, only when the car was idling in a closed space for sometime would it become noticable, which again I figured was coming from the rear of the exhaust.

and yes I've already showed my cousin the leak and told him we need a re-match lol.

Yes I used that orange silicon sealant and installed new gaskets a few months after the intitial install.

No CELs whatsoever.

You can see how the gasket wasn't ligning up perfectly on the side with the leak, seems to have been slightly low compared to the passenger side which eventually created the leak.

Reason for adding HFC is because I want to ship it to the UK and for me to pass MOT I would need to get them installed.

The bolts were tight, but could have loosened slightly with time. But not enough to make any noticable noises that there was something loose, visually they looked fine whenver I looked under the car.

I've had the exhaust on now for nearly 3 years so In theory I should have checked at least once a year and changed gaskets tbh.

 

Do you truly lose power with an exhaust leak?

 

^ Well my car dyno'd 370 Whp MAX with Full catless Exhaust and Headers and I should have been closer to 390Whp so I do believe it was a main factor for my car not getting the expected power with Headers and Exhaust.

 

Kclv numbers?

 

Ok well here is where it gets interesting.

I've only once managed to get my KCLV above 19, it sat at 20 for a week or so while data logging.

When I dyno'd the car it was around 19 that's the max I could get it.

Then I got the RR Racing Tune so my KCLV dropped and I had to do a bunch of runs to get it back up, eventually I put 103Octane in the car to see if it'll help raise my numbers.

The max that I managed to get it to was around 19.5 so even with the race fuel my KCLV wasn't above 20 (this is when I raced my cousin's E92 M3)

I'm planning on seeing my numbers now with the OEM exhaust and see how it changes and then Sea Foam the car to see if it'll help.

 

there's no need for silicone on the gaskets FYI. also, try LocTite on the bolts, but not the strongest one.

 

^ probably not needed for everyone but when installing aftermarket parts such as Headers and Exhaust from 2 different manufacturers and different installers then it does become applicable.

I'm mainly referring to the Header/Exhaust flange...from reading around I'm not the first one to encounter an alignment issue (could be down to the installation of the headers) either way the silicone gives me piece of mine and will be using it in future.

From the pics I posted you can see where I had the leak the gasket wasn't aligned center (it's slightly down compared to the passenger side) so with or without the silicone I would have still had a leak, but I'm guessing the silicone kept a seal for a lil longer until it gave way.