STI Exhaust Part Number - Page 2 - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

nikitopo · 05-10-2021, 03:59 AM

I have several logs on my car with the stock muffler and a few more with the STI muffler. In all the logs the maximum power appears after the change to be always 200-300 rpm higher, meaning that the engine breaths a bit better. So, the statement that there is a 13% lower airflow resistance looks to be true and measurable. I would say that this could be translated to a 2-3 bhp improvement at top end, but it is difficult to notice in daily driving. I haven't seen any other change in performance.

Dirty Harry · 05-10-2021, 04:28 AM

Quote:

Originally Posted by nikitopo

I have several logs on my car with the stock muffler and a few more with the STI muffler. In all the logs the maximum power appears after the change to be always 200-300 rpm higher, meaning that the engine breaths a bit better. So, the statement that there is a 13% lower airflow resistance looks to be true and measurable. I would say that this could be translated to a 2-3 bhp improvement at top end, but it is difficult to notice in daily driving. I haven't seen any other change in performance.

I thought something like that would be the maximum, I have heard catback exhausts give around 5hp on a twin. But yeah I don’t really notice it at all. I found a bigger difference in response by putting the lighter forged alloy wheels on.

gpvecchi · 05-10-2021, 04:12 PM

I had improvement in low torque. Perhaps it's because the STi muffler has longer piping than other exhausts?

RayRay88 · 05-10-2021, 04:46 PM

Quote:

Originally Posted by gpvecchi

I had improvement in low torque. Perhaps it's because the STi muffler has longer piping than other exhausts?

Maybe it's the throttle response from less restrictive muffler/piping that everyone is feeling. Piping length that far from the engine isn't going to make any difference. I bet back to back testing with the oem unit would give gains within the margin of error for a dyno. 1-2hp/tq max.

It's definitely an attractive part but the MXP SP is a fraction of the cost for a true cat back which makes it hard to justify the STi premium.

nikitopo · 05-10-2021, 05:03 PM

Not sure if it has been posted before, but the main reasons to go with the STI muffler is firstly the sound and secondly the appearance. It is not easy to understand the sound via a video, but there is an intensive explanation below (incl. English subtitles). Performance-wise the difference is so small that it doesn't really matter.

JCC · 05-11-2021, 02:09 PM

Awesome video. Thank you for sharing. Do want the STi exhaust for my BRZ if I can find it.

Elliotw · 05-17-2021, 10:34 PM

Video of 5k Rev with 2017+ STI muffler.
Full setup: EUL Catless header, Tomei OP, OEM Front Pipe, OEM Mid Pipe, STI Muffler

Chuckls · 05-18-2021, 11:55 AM

Calum · 05-18-2021, 02:29 PM

The only reason I went to an aftermarket muffler is because my factory muffler shit the bed. If thye factory muffler would last with a decent header I would have kept it.

Kauf · 02-20-2026, 07:41 AM

If anyone is curious like I am, here's an excellent comparison of the STI performance exhaust only (axle back) without other things added into the mix.

Takeoff & flyby:

And another:

Kauf · 02-20-2026, 07:47 AM

Quote:

Originally Posted by Calum

The only reason I went to an aftermarket muffler is because my factory muffler shit the bed. If thye factory muffler would last with a decent header I would have kept it.

I'm jokingly waiting for mine to go bad so I can excuse getting a new exhaust, but mine is still going strong from the factory after 12 years, several of which were driven in winter with all the road salt, etc.

02-20-2026, 07:41 AM	#24
Kauf Member Join Date: Nov 2012 Drives: 2014 SSM BRZ Location: FL Posts: 56 Thanks: 7 Thanked 14 Times in 8 Posts Mentioned: 0 Post(s)	If anyone is curious like I am, here's an excellent comparison of the STI performance exhaust only (axle back) without other things added into the mix. Takeoff & flyby: And another: __________________ Last edited by Kauf; 02-20-2026 at 07:57 AM.

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05-10-2021, 03:59 AM	#15
nikitopo Senior Member Join Date: Mar 2014 Drives: '15 BRZ RA Location: Greece Posts: 3,787 Thanks: 2,417 Thanked 1,947 Times in 1,263 Posts Mentioned: 29 Post(s)	I have several logs on my car with the stock muffler and a few more with the STI muffler. In all the logs the maximum power appears after the change to be always 200-300 rpm higher, meaning that the engine breaths a bit better. So, the statement that there is a 13% lower airflow resistance looks to be true and measurable. I would say that this could be translated to a 2-3 bhp improvement at top end, but it is difficult to notice in daily driving. I haven't seen any other change in performance.

05-10-2021, 04:12 PM	#17
gpvecchi Senior Member Join Date: Mar 2018 Drives: Toyota 86 GT Limited PP (Model G) Location: Italy Posts: 1,057 Thanks: 414 Thanked 361 Times in 203 Posts Mentioned: 14 Post(s)	I had improvement in low torque. Perhaps it's because the STi muffler has longer piping than other exhausts?

05-10-2021, 05:03 PM	#19
nikitopo Senior Member Join Date: Mar 2014 Drives: '15 BRZ RA Location: Greece Posts: 3,787 Thanks: 2,417 Thanked 1,947 Times in 1,263 Posts Mentioned: 29 Post(s)	Not sure if it has been posted before, but the main reasons to go with the STI muffler is firstly the sound and secondly the appearance. It is not easy to understand the sound via a video, but there is an intensive explanation below (incl. English subtitles). Performance-wise the difference is so small that it doesn't really matter.

05-11-2021, 02:09 PM	#20
JCC Member Join Date: Feb 2020 Drives: 2016 ice silver metallic Location: US Posts: 77 Thanks: 47 Thanked 17 Times in 13 Posts Mentioned: 0 Post(s)	Awesome video. Thank you for sharing. Do want the STi exhaust for my BRZ if I can find it.

05-17-2021, 10:34 PM	#21
Elliotw Senior Member Join Date: Sep 2017 Drives: '18 BRZ tS, '18 GTI SE, '11 RS Location: Seattle Posts: 505 Thanks: 232 Thanked 392 Times in 224 Posts Mentioned: 7 Post(s)	Video of 5k Rev with 2017+ STI muffler. Full setup: EUL Catless header, Tomei OP, OEM Front Pipe, OEM Mid Pipe, STI Muffler

05-18-2021, 11:55 AM	#22
Chuckls Moutain Runner Join Date: Aug 2018 Drives: BRZ Location: Atlanta, GA Posts: 487 Thanks: 23 Thanked 301 Times in 166 Posts Mentioned: 2 Post(s)

05-18-2021, 02:29 PM	#23
Calum That Guy Join Date: Dec 2011 Drives: 2013 asphalt FRS MT Location: Halifax, Nova Scotia Posts: 4,865 Thanks: 5,058 Thanked 2,868 Times in 1,499 Posts Mentioned: 82 Post(s)	The only reason I went to an aftermarket muffler is because my factory muffler shit the bed. If thye factory muffler would last with a decent header I would have kept it.

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