Planning to dyno the car during the off season. I have a baseline dyno, but the shop that it was done at closed down. So it won't exactly be an apples-to-apples comparison.

 

My car isnt STR, but I can speak for the difference I felt, and the sound level of my setup.

Car: 2004 S2000 AP2 (BSP)
Header: OEM, wrapped
CAT: Deleted by custom exhaust (not STR legal)
CAT Back: Custom 3" (from header flange) with Resonator and HKS Hi Power Muffler w/wo silencer
SCCA Sound Rating: 94db (without silencer) 92db (with) as measured at San Diego Nat'l tour

The test pipe and 3 inch exhaust makes the midrange in my car a night and day difference from an OEM AP2 (as compared between my car and a buddy's stock CR). The tune I am currently running on KPro was tuned everything with stock (cat/intake/header/exhaust); so the car has not been tuned specifically for the test pipe/exhaust. nmrado and random1 have both driven my car (althogh some time ago now) and may be able to speak for the butt dyno difference (granted they both have AP1s), but Weldon (the CR owner) said that my car had considerably more power througout the midrange and top end than his CR.

I would imagine the power difference of someone with an aftermarket header, high flow cat, and some sort of free flowing exhaust would be SIMILAR to mine. But I do not have any before and after dynos to support this.

 

With the PLM header, Magnaflow cat, and down pipe I can confirm there is a noticeable difference in feel (torque) in the 3k to 6k RPM range. The difference is more than turn the AC on and off according to my butt dyno. You can also feel the car pull harder above 6k. My co-driver likes it because he does not have to shift to first gear as much.

On the sound volume difference I was able to run the down pipe with OEM header and cat at the San Diego Tour and not get warned. With the header/HFC installed I got a 97 dB warning at nationals, so there is a definite difference. With the second resonator behind the v-band as a muffler the sound is still quite loud and I am concerned about running at the SD Tour next year. I am now considering a new muffler to ensure no violations.

 

I am looking into building my own exhaust. The current 70mm exhausts are very expensive for what you get. Has anyone done a custom 70mm exhaust? Can you even find 70mm mufflers or tubing? Would 2.5" be better for STR? I will be pairing the exhaust with a Berk 70mm cat and a PLM header, then tunning with Hondata.

Jeff Cawthorne

 

Go with a 3 inch system. I got great gains with the Berk on my car. It is a little loud but I will be putting another muffler in it just to make sure it stays under the limit.

 

just make sure you have a real muffler in the midpipe and not a resonator. My Mugen has a full size muffler in the midpipe then exits into 2 titanium canister type mufflers. That should take care of any drone that most aftermarket exhausts cause for the s2k.

 

Agree with this (3") if you are going bigger than 2.5 (63 mm). Parts are more readily available from Burns Stainless and Coast Fab right there in your area Jeff. Your are going to need a light weight racing muffler in order to improve on weight over the OEM resonator.

Burns Stainless
Light Weight Mufflers - Burns Stainless

Coast Fab
Light Weight Mufflers - Cost Fab

These are the places some of the Mod/Prepared Autoxers go for their mufflers. They also have 3" stainless tubing and other accessories.

I am considering this two stage muffler, but it is quite expensive at $460. It would go in place of the current OEM resonator.

Burns Stainless
2-stage
2.5" in and out
OD is 4.5"
Length is 17"
Weight is 3.8 lbs

 

Rob, I had the Burns single stage muffler on my M3 and I would not say it did much "muffling" of the sound level. It did make the car sound really good but it was pretty loud. The 2 stage may be better at reducing sound levels but it was just to expensive for me to justify when I made my exhaust. http://www.youtube.com/watch?v=0i6Pspes5a4

 

The cheap option: https://www.s2ki.com/s2000/topic/617...light-exhaust/
If you want to make it even cheaper, use regular 2-bolt flanges instead of fancy V-bands.

Cuts around 40 lbs off the rear of the car, sounds better than some very pricey exhausts. Resonates badly inside the cabin at 'normal' RPM, but it's stupidly easy to swap the rear mufflers back on after the event. After installing a high-flow cat, I feel it's a little too loud.

 

Anyone have a litespec, hopefully with sound measurements? It sounds like a great exhaust but I'm worried about sound levels. Locally we're supposed to be under 93 dB although they don't seem to enforce it unless it's really ridiculous. I could run a silencer locally. I'm hoping without silencer it's below 100 dB and with silencer it's around 93 dB...