chimmike

Back from my Nissan days, guys just starting really hardcore tuning the SR20 for n/a and messing around with the SR20VE tried throwing on 3" exhausts with aggressive cams and ended up really making some power.

Anyone other than Krazik running a larger diameter exhaust?

I know most JDM exhausts are 60mm, which is about 2.36". Probably decent for a street car, but if a custom expanding runner header was made to match up better with a 3" exhaust, say with a megaphone by burns stainless welded in for torque................could make for a very free-revving high hp S2000..........

or am I way off?

Say, larger throttle body with stock intake mani and 2.75" or 3" intake.........

AssassinJN

70mm exhaust is just over 2.75" (see amuse, j's racing, etc), 80mm = 3.15" (see feel's etc).

This car has nitrous, but i'd be curious to see what it runs NA.
http://www.hondatuningmagazine.com/feature..._jdm_parts.html

Generally the consensus seems to be anything over 70mm, or even 60mm on our car does not make significantly better hp compared to the increase in noise.

dparm

I doubt you need 3" on an NA S2000, unless you're running some crazy high CR. Too big and you destroy flow quality.

chimmike

one could easily argue that 11:1 stock compression is ridiculously high.

I know what you're thinking and I used to think the same thing, but I'm thinking under the proper setup, 3" exhaust could definitely make power.

Krazik (name right?) is running 3" exhaust, look in the dyno thread.

Q8s2k

This is interesting, recently i'v been visiting the K20 forums coz i wish to do a K20 swap into a civic Hatch and i noticed that most of them are using a 3" exhaust setup..

On the K20 forums, they have dyno sheets of a 3" catback vs 2.5" catback... This guy gained 10whp going from 2.5"(63mm) to a 3"(76mm) with a K-pro tune..

"The 211whp run was from June 16th. The 217whp run was the preliminary pull with the 3" exhaust, and after some tuning, the final number was 222whp, only 30 minutes apart."

http://www.k20a.org/forum/showthread.php?t=46317

Mods: stock internal K20A2, an RBC intake manifold, 11" intake with velocity stack/filter combo, long-tube Tri-Y header, and tuned on K-Pro.

The K20A2 has a compression of 11.0:1, almost the same as our S2k's..

HvRRZ

I was running a custom 3" system on MY04(and will be again soon on MY07), and had no issues of loosing torque or hp.

The car made power throughout the entire powerband with the exhaust system and full bolt ons.(all on stock ecu) made upwards to 230whp and peaking at 170wtq. In the lower rpms I was consistantly around 150-155wtq until vtec engagement.

Bottom end felt great, but top end is where the car really came to life. The car ran much smoother, and it took a lot less effort to climb to redline.

I had a hytech header, and made the 3" system using a transition pipe which started as the same size as the collector of the header, and went into a 3". From there the rest of the system was 3" piping. For my 07 it'll be matted to a custom header that will have a 3" exit also.

If you can go 3" then do it....don't believe the nay sayers.

chimmike

The problem now is, the naysayers don't have any evidence.

This is how I view it. Over the past 8 years, small engine development has gotten so advanced that small engines now flow levels normally held for older larger displacement vehicles. Allowing the velocity to be maintained on exit from the motor via the 3" exhaust allows the 4 bangers to breathe better and pump more efficiently than before.

I'd be interested to see an f20c with the mods I described.

Maybe I'll have to build a 3" exhaust from my berk header back and test it out sometime.

Q8s2k

Inlinepro have a 3" exhaust for $695, Looks like a great piece...

would be nice if some dynoed it on a stock S2k or with Bolt-ons..

Ryan2lot

3" exhaust on a NA s2000 will make power, but lose torque without a tune. If you can stand the loudness, go for it!

chimmike

You can run a good resonator and muffler with 3" exhaust and it won't be too unbearable, IMO. Either way......without a tune nothing would do any good!