i have a 12:5 compression, jdm itr header, jun 3 cam itr... and am considering either getting a new 2.25" exhaust from teh header back... or 2.5" piping to a 2.25" muffler... or 2.5" piping back. The thing is... the only reason id even consider the smaller piping is because:

i can get an itr catback for cheap
i like a quiet exhaust
im low on cash

so... how much performance gains do you think id lose with teh small piping... or just small muffler.

 

jun recommends 3" straight through. lol.
id stick with 2.5"... prob is youll lose even more low end then with 2.25"..i guess it just depends on the application.

 

i'd say stick with any catback exhaust system thats 60mm
which is bigger than 2.25 inches just a tad.

when u go to a bigger bore as in 84mm+++
then it'll be time to go with a bigger exhaust for more gases your burning
2.5 inches would be needed than

 

Do your exhaust once. It will be cheaper in the long run. If you don't have the money for a 2-1/2" system now, just stock with what you got but at a minimum get rid of that bottle neck, especially if you are running a JDM header.

 

Sam, the ITR system is more like 2", not 2.25"

 

I was running into the same question...I have 60 mm piping exhaust w/ JDM header & test pipe. I was thinking of re piping it to 2.5, but still wouldn't there be a bottleneck where the piping meets the muffler? Would that be just as bad?

 

well igot a full itr exhaust for 150$... so im gona use that