My future plans for my 97 GSR are intake, header, exhaust, ctr or itr intake cam and a hondata s100 to tune after installing the cam. I was thinking about getting a JDM ITR 4-1 header or comptech 4-2-1. Which ever one I get is going to be followed by a high flow cat and the same size piping all the way back. I was wondering if 2.5 inches would be too much for the mild mods. Do you think I am better off going with a comptech header instead?

 

I say definately. If the jdm spec dc sports header didnt sit so low, I would go with it. but anyway, see for yourself:

http://bob123e.tripod.com/thegreatheadertest/

 

DC Jdm 4-1. Cheaper, better ground clearance(i think), and just as much power.

 

If you want a 2.5" collector and good ground clearance, go for the A'PEXi GT header for the '98spec JDM ITR. It's a 4-2-1 design so it keeps itself up from the ground more than the 4-1 designs.

You'll also need a 2.5" cat and 2.5" exhaust to get the full benefit of the header. Kteller sells what they call a "bolt up piping kit" which is essentially a set of pipes that you bolt on and add your choice of muffler (which they also sell).

If you're not modifying the engine internally, then the gains you see from a 2.5" system over a regular bolt-on header and a regular aftermarket exhuast (most are 60 mm piping which is like 2.36") will be maybe 3-5 hp tops. ITR motors and GSR motors with cams respond better to the 2.5" exhaust than a stock GSR motor.

 

I was thinking about getting the 98spec JDM ITR header because I could probably find one with heat shields and it would look stock when I go to smog my car or if for some reason I get pulled over. Keep in mind that I live in California. Is the A'PEXi GT header carb legal? If I get the JDM ITR header, 2.5" carsound cat and 2.5" piping, I should pass smog as long as I run a cat right?

 

Well, being as I'm not from California I don't know what exactly will or will not pass.

The A'PEXi website doesn't mention anything about CARB exemptions so I couldn't tell ya one way or the other on that one. My guess is that even if the bolt-on versions are exempt, the 2.5" collector version is not because it is designed for a car that was not sold in this country, that being the JDM 98spec ITR.

I'm guessing that if you have a JDM ITR 4-1 with all of the heat shields in place for the header and catalytic converter then you won't raise any eyebrows such that they would even look for a CARB sticker. If you're looking for a place to get the heat shields this is one possibility although I'm sure it's available elsewhere. Technically this setup is not legal but you should pass the sniffer test and not have any CEL codes, so who cares about a technicality? If you're trying to be stealthy I'd probably go this route.

Oh and about the Kteller exhaust: I would suggest the 2.5" stainless bolt-up piping kit with an 18" resonator, and either the 2.5" turbo-style or 2.5" dual tip muffler. They can also probably weld you up a Carsound cat with the proper flanges and oxygen sensor bungs, although they don't have it listed on their site.