Perrin 2.5” cat back issues
 

Hey all, after a bit of advice. I picked up a second hand Perrin cat back recently. The reason I searched for a Perrin is the thousands of reviews all over the internet stating it doesn’t drone.

So, now it’s installed it seems to be really ‘boomy’ between about 1800 and 3000 revs, even to the point that the garage door vibrates significantly while it’s idling. It is VERY deep in the low rev range and causes quite a bit of volume in the cabin at low revs. Outside of this zone it’s actually pretty quiet.

It was originally a non-resonated version, but the previous owner had a decent sized resonator welded in where the Perrin one would be (prob close to equivalent size). I thought this may be related, but most online feedback seems to indicate that even the non-resonated 2.5” Perrin doesn’t drone / boom. I can’t imagine the introduction of a resonator would create drone?

I saw quite a few people have had resonance issues from the clamps not being tight / aligned. I triple checked this and even had an exhaust shop check (with a stethoscope) - no leaks. The only thing left that I thought it could be is the rear muffler itself? Perhaps it’s lost its internal baffling over the years? Could this be possible? Are they repack-able? Anyone had a similar experience with a Perrin (no other exhaust mods)?

Any advice you may have would be appreciated. Thanks.

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Buy the exhaust hangers as per this thread: https://www.ft86club.com/forums/showthread.php?t=143514

Thanks heaps mate. Seems to be mostly the deep note coming from the exhaust (even when standing behind) rather than vibration coming into the cabin per se, but definitely worth a shot [emoji1360]

I've read the Perrin gets a little louder with age. Maybe reach out to Perrin to see what they suggest?

Thanks mate. I had wondered that. Seems the muffler itself is quite loud and boomy. Not sure if they can be repacked. I’ll give the hangers a go first and see if that makes enough of a difference.

It could also be the unknown resonator that was welded in that needs repacking.

For reference I have the resonated version of the perrin 2.5" but also a catless header, and hiflow catted mid-pipe. Other than on cold start I wouldn't call the setup loud or boomy. I guess we all have different tolerances and expectations of volume tho so YMMV. Volume wise I think my setup is on par with something like an HSV :iono:

Thanks mate. Yeah, replacing the resonator is another option. I figure it an unlikely cause given the unresonated Perrin doesn’t seem to drone / boom (online accounts at least), but def worth a shot if needed.

I’ve had (and still have) quite loud exhausts on other cars in the past, but main aim was to keep this one relatively tame as the daughter spends a lot of time in the back on long trips etc (recently 3500km). The noise isn’t horribly loud, but just unexpectedly boomy based on other accounts.

Hoping the hangers will make the small amount of difference needed. Resonator prob next In line following a chat with Perrin to get their thoughts.

Perrin 2.5” cat back issues
 

Ok, so fitted 5 of the exhaust hangers a day or so ago and have driven it quite extensively since. They made a slight difference, but it was minimal unfortunately. Its an improvement, but I didn’t think it was a resonance problem necessarily, more just the really deep boom that comes out the muffler at low revs. I had my wife drive the car past me and at low revs and minimal acceleration you can literally feel the boom coming out the rear as the car goes past.

Don’t get me wrong, it’s not RIDICULOUSLY loud, but between 2-3k under load or under deceleration it’s just not enjoyable. I have an exhaust on one of my other cars which is probably twice as loud volume wise (no joke), but it’s a ridiculously enjoyable noise. This is just boomy and not a nice sound. It does sound great from 3k onwards and is nice and deep at idle though.

I’m a bit stuck what the next move is. Really wouldn’t consider it to be the aftermarket resonator, but I’ll talk to the local exhaust expert about that. I’ve also contacted Perrin to get their thoughts. My inkling is, although it looks great externally (no rust, no crazy heat marks), the rear muffler has had it or lost it’s packing etc.

I am considering a Catted UEL header as at least this would make the lower noise less constant (ie the rumble might make it more enjoyable to hear). Not sure on this though.

Has anyone else with a perrin 2.5” cat back had this problem? Possibly with age?

If you're running an un-catted header, then yes getting a catted header will quiet things up significantly. I have a very similar design exhaust -Greddy Supreme SP but with catted UEL header installed 2 weeks ago.

Ironically, I have to take my wife's Mazda3 in for service in a few hours. So I was able to hear it just a moment ago driving away. Lovely quiet tone driving away. I will admit between 1k-3K mine is also a little boomy in the cabin when driving but I love it lol.

Also, a good tune will change the exhaust note a little if/once your tuned.

Thanks mate. Just stock other than the cat back. Wasn’t planning on a tune at this stage at least.

QUESTION: is anyone possibly able to measure the length of the resonator on their Perrin cat back?

Thanks in advance.

It’s about 24” from inlet to outlet. Sorry not sure why this picture is showing upside down but you get the idea.

Love your work. Thanks mate.

Those hangers made a lot of difference for me. Sorry to hear it didn't work for you. I have the "proper" resonated version though. Mine is paired with PSR UEL catless header and tuned for E85. If you can't cope with the stock header, maybe reconsider... It doesn't cover the exhaust sound, everything goes up a notch. I also have a liner in my car, it helps a bit too for longer trip, under the boot mat: https://www.carbuilders.com.au/mass-noise-liner. I think the "boominess" is just that exhaust note, you will never get rid of that note. Maybe just go back to the stock exhaust with your headers. Over here, a lot of the guys at the track don't bother with the catback as there is not much gain.