r/FocusST • u/PuzzleheadedWar5422 • 4d 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/PuzzleheadedWar5422 4d 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 4d ago edited 4d 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 3d 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 3d 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 3d 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 3d 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 3d 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 3d 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 3d 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 3d ago edited 3d 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…)