Hey man,
I am only using a 3 inch from the header all the way to the tip no 4 inch anywhere.
I am supercharged so it would be different for you.
I do know that the whole back pressure thing does not matter much if at all on our cars due to the rev range.
Back pressure is for bottom end power which we dont have anyhow.

as for dyno I do have one but like I said its F/I so way different.

ACEKING,
No sound clip but I will be at Infinion Raceway next weekend for SCCA if you wanna come hear it
when on track where the sound booth picks me up its around 102 Db

 

I think Berk is working on a 70mm header back.

 

If you have access to a dyno why not play with different mufflers and piping diameter just use clamps to keep em together ; )

 

It's not back pressure that helps exhaust flow, it's the power pulses coming out of the header that create a low pressure that pulls the following exhaust from the engine. That's why a header's design is so important. Having some piping after the header junction is needed for low and mid-range power. A dragster doesn't need midrange power so they can run individual exhaust pipes for each cylinder.

Turbo and supercharged cars normally benefit from very large exhaust pipe or even a dump at the turbo, but you can go too large for a NA car.

 

https://www.s2ki.com/forums/index.php?showtopic=710752

This thread made me rethink the whole s2000 needs no back pressure.

 

It's not back pressure, it's exhaust velocity. A smaller pipe gives faster exhaust speed which helps pull the exhaust out of the engine.

 

We want to make our own circuit system, firstly to try to gain more than other ready-in-the-market systems. Secondly we dun need low-end for this system. Thirdly it will probably be cheaper. Noise level is not a concern, except for driver fatigue and inability to pick up other sounds. The track we run on is the Sepang F1 International circuit in Malaysia that is shown in my signature. There is no residential anywhere nearby so they dun slap on any restrictions.

crash: Icic...I guess FI would be totally different in application but thanx fer the input! We are staying all-motor with our build.

robrob: Thanx fer sharing the info.

Ok I think I get the whole backpressure myth and exhaust velocity theory...... In short, Maximum Exhaust Velocity with Minimal Backpressure for Target RPM range.

 

I'm thinking about running the inline pro 3" mainly because I know I'm going to boost it someday. I really can't see the S losing any more power than the stock exhaust. It's only .25in bigger than 70mm. Anyone run this exhaust n/a? Also, it doesn't have a resonator so it should shoot fireballs...