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  • 4 years later...

Bump.

Interested in this too, new exhaust tomorrow, was originally going for 2.5", but am looking at 3" after some reading. No point going to 3" with the standard dump and front pipes if they're only 2.5"...

stock r33 is 2.5" just measured my stagea one, its ok to go from 2.5" to 3" cause after a while your exhaust gasses will cool down and expand so technically going from 2.5-3" is perfect. also a 3" down pipe costs bugger all these days.

also from memory, the top half of your dump pipe is 3" and the bottom piece is 2.5"

stock r33 is 2.5" just measured my stagea one, its ok to go from 2.5" to 3" cause after a while your exhaust gasses will cool down and expand so technically going from 2.5-3" is perfect. also a 3" down pipe costs bugger all these days.

also from memory, the top half of your dump pipe is 3" and the bottom piece is 2.5"

Cheers mate. thumbsup.gif

Searched and bumped a dozen threads looking for this answer! I'm having problems with the car dropping boost after 4000-5000rpm. Given it's only running ~5psi and dropping to ~3.5-4, there has to be a restriction somewhere, and given that a GTST runs 9psi after 4500rpm, I doubted it'd be the dump/front pipes.

So 2.5" should be perfect for my needs, and a good step-up over the N/A cat, center pipe and center muffler.

2.5" mandrel is good, but a proper 3" system is always best and will see you get better figures. i went from original to JJR 3"- 3" stainless cat 175cell- HKS hi power silent 3", made noticable difference, but currently running split front pipe, 3" no cat and a straight pipe with HKS endpot. makes even bigger difference then with a proper system, sounds nicer too, but not a very wise choice! EPA, cops, etc

if yours is blocked, try swapping out the cat, if its not that, you could have a blocked Muffler, so to recap, only go to 2.5" if you dont plan on upgrading anything! go to 3" if you want more headroom

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