2.5"-3" or full 3"

[13secGST]

ok I eventually plan for big 16g a supporting mods and I have a Tanabe RM 3" cat-back right now. I want to get a test pipe and downpipe. My Tanabe necks down just after the cat and then opens up. To be able to do full 3" I would have to cut a piece of the Tanabe off and have a 3" part welded on with 3" flange right? and then for emissions I would have to find some kind of 3" cat right? Well anyway I was thinking do I need full 3" or would it be good to go with 2.5" dp and tp so I could switch the tp and cat easily and not have to mess with cutting my Tanabe. Would the 2.5" cause me to have more boost creep? Just want opinions and experience, Thanx

 

[red91GSX]

you should be able to shake off the 13's with a 2.5" dp and test pipe - but if your prone to getting hooked on power, just go with the 3" dp also and port the hell out of your manny/turbo/o2 sensor. they're usually about the same price anyways.

i have a stock dp into a high flow 2.5" cat into a full 3" catback and i have no boost creep

 

[13secGST]

wow, fast reply. Thanx yeh I only plan for low 13s and then if I want more maybe 12.5's which has all been achieved and is proven with a big 16g and supporting mods. Basically I guess my first question was how much of a pain in the ass would it be to do all that stuff with the exhaust. and where the hell will I find a 3" cat, or will I pass emission with a 3" high flow?

 

[zac83]

if you have a 'high flow' as we like to call it: no ... all that is is just a little glasspack muffler. 3 inch cat = large vehicles... something you might try is to get a larger vehicles cat. i would sudjest a lightning (if they are single exaust...) or another high-po larger block engine that comes with single exaust. one thing you might look into is a celica GT-S, the stock exaust on thoes is monster... like 2.75 or 3 inch out of the header i believe...

but i have seen crazier stuff, if your AWD, you shouldnt have to worry about emissions if you can tune your car with an afc or computer... awd = no rolling dyno tests, just idle butt dynos... and idle butt dynos, while sounding dirty, are so simple to pass... ive seen crazy modded 02 SS camaros with strait pipes pass butt dynos with flying colors...

change your oil before you dyno.... mist water into your intake from a squirt bottle every time you run your car for a few days before you dyno it, dont put garbage-trash octane boosters in your fuel... run goooood gasoline from the same station for atleast 2-3 full tanks before you dyno... make sure your heated 02 sensor works.... remove your o2 sensor and test it with propper methods. take off your twankeys if your running them and your on a fwd car that they can dyno. make sure your car is warm.. no... hot when you take it in... drive it calmly before you take it in, i would sudjest steady freeway driving at 70 mph before emissions dyno.

if you dont pass, slip the ####ers 50 bucks and be on with your day

 

[Black_90TSI]

I have a 3in ATR from the downpipe back it sems to do the job great w/ the big 16g.