Another exhaust question for ls1

[johnno010684]

i have tried looking on here but cant find anything about outlets and cat sizes for my exhaust, i have a vx clubsport with standard extractors and cats, then a twin 3" cat back system which i fit myself. i plan on doing mafless tune after exhaust is finished and a cam later down the track, so was the reason for going 3". what size extractors should i be looking for? ones with a 3" outlet or not? and what size cats/cat sections should i be looking at?

[Lumps of cheese]

Headers, mabye 4 in 1's with 1 7/8 primarys would be the go.

[johnno010684]

ok, i have found a bit of info on the standard vx clubsport extractors and there are many different opinions, basically i dont want to spend 6-900 on a new set if im only gona see small gains. does anyone know how "free flowing" the hsv cats are? or should i just replace the cat sections with high flow cats and 3" pipe?

[Vt_vic]

the stock hsv stuff on the vx is crap but if you have to just get cats but they will have to be 2.5 inch in and 3 inch outlet to match the twin 3 catback.but if your getting a cam go twin 3 all the way

[QldKev]

If you are looking at cam work

1 7/8 primaries long, into 4 into 1, 3 inch collector
3 inch metal cats
your 3 inch exhaust.

The stock 2 1/4 cats can be opened up to 2 1/2 inch, but by the time you hit 3 inch your pushing shit up hill.
Also with the extractors and 3 inch your exhaust will sit lower, so you are better of with metal cats so if you bump them they will not shatter.
The cats should be at least 200CPI, or 100CPI if you can get them for a decent price. (lower number the better)

QldKev