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Was looking into getting new cats for my car, and thought I would check in to see what others are running with. I know certain cats don't play well with certain exhausts, so I was hoping to get some good advice from someone with experience. I just purchased a Stillen catback over Black Friday, but haven't installed yet. I like to get the opinion of vert owners specifically because I feel our cars are a bit different from the sedans and coupes.
I'm still searching for that ideal growl. :/
So far just running IPL axleback as all catbacks I've heard are too loud for my liking (or way overpriced - gthaus).
I have the Stillen cat back exhaust and now have z1 motorsport hfcs. I dont think it is too raspy or loud but that can be very subjective depending on what you like or want. From what i can tell tou cant trust Youtube videos you got to get people that have set ups to meet you and let you hear it in person.
Was looking into getting new cats for my car, and thought I would check in to see what others are running with. I know certain cats don't play well with certain exhausts, so I was hoping to get some good advice from someone with experience. I just purchased a Stillen catback over Black Friday, but haven't installed yet. I like to get the opinion of vert owners specifically because I feel our cars are a bit different from the sedans and coupes.
Which cats give the best gains and sound?
Are there really any hp gains running an after market cutback? It's still a single exhaust, restrictive system?
I like to get the opinion of vert owners specifically because I feel our cars are a bit different from the sedans and coupes.
Which cats give the best gains and sound?
Insofar as sound goes, its certainly a fair consideration when your roof is down. And while feeling unique is a special thing, regardless of what you feel about your Vert being a bit different, at the end of the day it's just a Coupe with a retractable hard-top. Now, if you had the Vert 6MT, then you'd have really short 3.916 rear gears, and that would certainly be something special when comparing different models of the same car. But in the context of exhaust considerations, it's just another G37... Coupe vs. Sedan notwithstanding.
IMO, any change you perceive in power will be a negligible difference from one aftermarket cat to the next... because any exhaust mod like this will be a compromise of small added power over noise and catalytic efficiency.
For sound, I strongly recommend resonated cats, which I believe are FI and Ark only, where FI use traditional little resonators, and Ark uses a Helmholtz design which is extremely loud, but oh-so-sexy. There really aren't a lot of options, so it should be easy enough for you to research. And I make this recommendation for resonated cats in no small part because your roof might be down.
Originally Posted by 74pantera
Are there really any hp gains running an after market cutback? It's still a single exhaust, restrictive system?
Actually, it's a header, dual exhaust with an x-pipe... two cats, two big resonators, and one giant muffler collecting and splitting the exhaust out back. The pipes on the Coupe and Vert are slightly larger than the Sedan (which uses two separate mufflers) and the in-line resonators are at a slightly different position, which is why the Coupe/Vert sounds different.
The OEM exhaust is vastly less restrictive than most cars, although more so than aftermarket designs. So yes, there will be noticable gains when modifying your exhaust...
Actually, it's a header, dual exhaust with an x-pipe... two cats, two big resonators, and one giant muffler collecting and splitting the exhaust out back. The pipes on the Coupe and Vert are slightly larger than the Sedan (which uses two separate mufflers) and the in-line resonators are at a slightly different position, which is why the Coupe/Vert sounds different.
The OEM exhaust is vastly less restrictive than most cars, although more so than aftermarket designs. So yes, there will be noticable gains when modifying your exhaust...
... even on an incredibly heavy Vert. [/QUOTE]
So, I guess I'm missing something, I was talking a catback, and you're talking about an entire after market exhaust system? Just curious, what kinda HP gains are we talking about? How much for the entire system? It's never going to be enough to propel the 2ton drop top with any oomph!
Like you said, it's a lead sled, albeit a beautiful one. It's never going to be a "fast" car. Thankfully for this OG, I have a few fast cars so my Vert is my daily driver.
Thank you for the knowledge and response!
Last edited by 74pantera; 02-09-2017 at 09:05 AM.
Reason: spelling error
OEM shorty headers dump into separate catalytic converts on both sides, which then collect and split again into resonated mid-pipes, which then collect again into a single large muffler with two outlets. To your point, it's not a true-dual exhaust because of the collector design and the single, double-duty muffler, but I sure wouldn't call it a single-exhaust.
Not sure how you would label it, actually.
When replacing cats or catback:
Increased noise from each? Yes.
Gains from aftermarket cats? Yes.
Gains from aftermarket catback? Yes.
Gains enough to notice from each? Yes.
Gains that really, really matter from a performance POV? Nah, but that's subjective.
Originally Posted by 74pantera
So, I guess I'm missing something, I was talking a catback, and you're talking about an entire after market exhaust system?
The OP was talking about cats. It's his thread. Whereas you're talking about catbacks, and I'm just rambling on about the entire exhaust.
Originally Posted by 74pantera
Like you said, it's a lead sled, albeit a beautiful one.
The coupe and sedan resonators are not in different positions. The coupe resonator is just about 5" shorter than the sedan. Same mounting point under car, same connection at y pipe. The axle back portion on the coupe uses 2" piping while the sedan uses 1.4" piping. The cheapest route to go to increase power is taking your stock y pipe and mid pipe, cut off the y section, install a x pipe and install resonated hfc's. Most aftermarket exhausts utilize 2.25" piping vs OEM 2" which probably makes no difference in power.
The coupe and sedan resonators are not in different positions. The coupe resonator is just about 5" shorter than the sedan. Same mounting point under car, same connection at y pipe.
Corrected, thanks. Filing that away it the back of my head.
AAM HFCs and also AAM Y pipe - then mapped her with Ecutex so whether you get anything just from the HFCs or whether it was the Ecutek that did it . . . . who knows.
However, I liked Rochster's comments -
Increased noise from each? Yes.
Gains from aftermarket cats? Yes.
Gains from aftermarket catback? Yes.
Gains enough to notice from each? Yes.
Gains that really, really matter from a performance POV? Nah, but that's subjective.
If the noise is better you can bet your trouser dynamometer will tell you it's going better. It feels a bit more to me . . . . but having spent $1000 on hardware and $1000 on software it's absolutely going to feel better, eh!
I always thought of the HFCs and the improved flow with a better Y as part of the same breathing improvement. It does make it louder, and give it a bit more rasp - I quite like that but it's always a personal thing.
I also found the stock sound was too quiet and the modest bhp gains were almost incidental to the sound improvement - I'd found her so quiet you had to glance at the tacho to see the revs but afterward you could hear what revs you had on - so I thought that was safer, too (I hated glancing down mid corner just to see the revs)
Anyway, I thought the sound improvement pretty good, but I guess you'd need to hear it for yourself.
(I can't send you a clip of mine as February in Manchester in the UK, she's not going to be doing anything spirited over here, I'm afraid)
12-07-2016, 01:34 PM
Filing that away it the back of my head.
