Would putting an 01 ITR header and exhaust onto a 00 Civic Si give decent gains?
And does anyone know if it is a simple bolt-on or will I have to cut and weld to get a decent fit?

I know that the ITR is 2.25" but what is the size of my Si? Is it not 2.25" also?

If the Si is 2.25" also, then will the ITR header and exhaust be worth even messing with?

I'm guessing there would be a noticable difference, otherwise why would Honda put a different exhaust on the ITR versus the GSR.

I've done a search looking for info on this but I've found nothing that was helpful. Thanks for any input.

 

both are 2" not 2.25
you will see a gain over your stock system, but it wont fit 100%.

 

Is that right?
I was always under the impression that they were 2.25"


Anybody else?

 

can't you just wait until tonight when we take it all apart and measure it then? ya lazy ***!

 

NO!!!

I must know now!!!

 

I installed an ITR header and cat. on a '99 Si and found some slight gains (mostly in the upper RPM range), which wasn't bad since the mod. cost me nothing. The only difference between the manifolds is in the lower half, so I would attribute most of the gains to the ITR cat. and the slightly (very slightly) larger collector of the ITR manifold.

Before I installed the pieces I also opened the ports to match the manifold gasket openings, and I smoothed out any welds and opened up the collector slighty, so I'm not sure if that had any effect on the gains as well.

Overall - not a bad mod. if the price is right, but probably not worth it if it costs you much for the parts.

 

I hear it give TONS of gains. Now who wants to buy my stock exhaust manifold and cat?