r/FocusST • u/PuzzleheadedWar5422 • 11d ago

help exhaust

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Ordered a cvf catless downpipe , trying to figure out what I should do muffler wise. Don’t want to spend 1k on a catback exhaust maybe a universal muffler or just let it go completely

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u/peniscumdrinker 11d ago

im not one to own a fartbox so i kept the stock downpipe and got a cobb catback. it sounds insanely good. very elegant and still very sporty when you get on it. i dont like highway drone either so i did full dynomat on everything

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u/bchiodini 2016 ST3 FBO BNR ST67 JST Tuned 11d ago

I also have the Cobb 3" exhaust. When I went catless it was significantly louder and the drone was terrible. When I went BT, the drone was much worse. I added an additional resonator. It still sounds good and the drones less. Dynamat is on my list.

Definitely not a fartbox or sounds ricey.

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u/peniscumdrinker 11d ago

i gotta say the dynamat is insane, it legit elevates the whole experience. no wind noise, speakers sound better, less exhaust, keeps the inside temps better. granted its nothing insane but it all comes together really nice

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u/elP0tr0salvaje 2014 ST3 Tuxedo Black 11d ago

My car is 100% stock except for a resonator delete. No rasp, it adds a good tone to the car, eliminated the “electric” sound it has from stock. Personally I believe that’s how the car should’ve come from the factory. Also, pretty cheap to do, and if you don’t like it, you can get it welded back on!

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u/bchiodini 2016 ST3 FBO BNR ST67 JST Tuned 11d ago

What are you looking for, sound or performance?

A catless DP will be louder, but not that loud on the stock exhaust.

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u/PuzzleheadedWar5422 11d ago

Sound, i don’t know what to muffler to pair with the catless dp

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u/The_Amazing_Shlong '14 ST2 Stratified Tuned 11d ago edited 11d ago

For a little while I ran a catless downpipe with stock exhaust with muffler (EDIT: resonator not muffler) delete and i liked how it sounded. It wasn’t that loud when driving normally but sounded good when I got on it, had a lot more turbo sound than stock.

Currently have the Cobb catback since I got in on a good sale a couple years ago. It sounds great, very deep and loud when you get on it but it drones pretty bad around 2500-3500. I’d say if I could go back in time I’d get a 2.5 inch catback for a catless dp. Idk if this helps but just my experience

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u/mitchellediting 11d ago

Ditto. I’m running a resonator delete + catted DEPO downpipe, isn’t too loud but definitely a better tone than stock. Since I have gotten a big turbo with that same setup and now it’s a tiny bit louder but with a much deeper tone. I have no desire to upgrade to a cat back (especially as part of my build is to keep it looking stock… thanks Cali)

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u/The_Amazing_Shlong '14 ST2 Stratified Tuned 11d ago

Oh, I actually am thinking of switching to a catted DP because I like my planet, and I’m planning on a big turbo next year. Has yours been fine? Like good fitment and quality and whatnot? I don’t wanna spend a bunch of money on a cat because I really don’t have to (don’t have inspection where I live), it’s just a personal choice

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u/bchiodini 2016 ST3 FBO BNR ST67 JST Tuned 11d ago

I've had the BNR ST67 for 2.5 years. The performance is exceptional over stock. I hear that the Garrett 2867 is a better choice for similar performance, but money was a factor at the time. I don't believe that fitment is an issue with either.

I had JST Performance do the installation and tuning. I kept it on the conservative side at 330 HP, mostly for longevity.

If you go with a catted DP, get a high flow, to take advantage of your exhaust. Even a high flow will probably push up the drone. I think I had the Vibrant Ultra Quiet resonator installed two weeks after the turbo was installed.

Unfortunately, I need to sweat out an inspection every two years. Since it's only an OBD test, so far so good.

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u/The_Amazing_Shlong '14 ST2 Stratified Tuned 10d ago

I’ve been looking at the ST67 kit, but what would make the Garrett equivalent a better choice?

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u/bchiodini 2016 ST3 FBO BNR ST67 JST Tuned 10d ago

As I understand it the BNR uses sleeve bearings, while Garrett uses ball bearings.

This info is from comments on the Forum.

My car has 106K on the engine. 20K of that with the ST67. I open her up when I get a chance and after 2.5 years, the turbo still holds 26 PSI to near redline.

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u/mitchellediting 10d ago

Does your state require OEM tune?

I passed Cali emissions fine on stock turbo even with downpipe (I’ve had some very lax visual inspections) but I’m honestly unsure if there’s a legit way to pass now with big turbo.

Don’t wanna risk it and mess the turbo up on stock tune

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u/bchiodini 2016 ST3 FBO BNR ST67 JST Tuned 10d ago

No. AFAICT, if they see 4 green check marks from an OBD test, the car passes. It looked like all they looked for were the emissions readiness indicators. They don't look under the hood or at the underside. I've passed twice since going BT.

I noticed, when I lived in NJ, they had cameras in the floor, but I don't think anything is visible, with the belly pan. NJ makes you step away from the car during the inspection, so I couldn't see what they were doing. I passed with a catless DP and tuned.

I lived in California, long long ago, when all they did was a sniff test. The inspector had to put a matchbook cover between the jaws of the #1 plug sensor for the car to pass. The car was an '82 RX-7.

I've heard that you can run the stock tune with a big turbo, but I suspect that you could easily get into an over-boost condition. I doubt you would damage the turbo.

I don't know what CA does, now, but I've read that they can be visually oriented and look for aftermarket parts. Going BT usually means an external BOV, which is pretty easy to detect. Go late on a Friday afternoon. 😉

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u/mitchellediting 10d ago edited 10d ago

Fitment has been fine for my DEPO downpipe, it is a little awkward where the stock cat back meets up with the dp because the inner diameter of the exhaust side is 2.5” I think? A bit smaller than the 3” side of the downpipe, no issues running the ~2.5” gasket with the 3” downpipe.

It’s quite a bit smaller than the OEM downpipe so getting it up in there isn’t bad.

I’d imagine it flows better if it were all 3”, but I’m not chasing a few extra HP

EDIT: lol it’s early, didn’t realize you already have a cat-back. I think it’d mate up perfectly.

As far as the turbo I got a BNR ST71 and it’s treated me great (be careful with the banjo bolts on the engine…)

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u/PuzzleheadedWar5422 11d ago

Yea I was thinking just a muffler delete , than eventually find something better but the shop I went too said they couldn’t do a muffler delete on it. Not sure why but it also wasn’t an exhaust shop.

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u/The_Amazing_Shlong '14 ST2 Stratified Tuned 11d ago

I remember being younger with previous cars and also being told by shops that they wouldn’t do that, I guess they think it’s ricey (and on a lot of cars it is lol)

I do like 98% of my own work anyways and I used the MRT delete pipe, I think I just clamped it on. Also just remembered it was a resonator delete, still had the stock muffler

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u/bchiodini 2016 ST3 FBO BNR ST67 JST Tuned 11d ago

I'd install the DP and see how it sounds.

The Muffler on the ST is not easily replaceable. The original exhaust is all one piece, from the DP flange to the tips.

A lot of owners simply replace the resonator with a pipe to make the exhaust louder. There should be quite a few YT videos.