3" exhaust necessary?

[Mindz]

I have noticed that Hennessey and LPE both use Corsa 2.5" catback/axlebacks, yet most tuners are telling me that 3" is necessary for getting rid of the backpressure completely.

Have there been any tests that show if one is better than the other?
Is eliminating backpressure in the exhaust completely a good thing?
Is a 3" exhaust all the way through necessary for forced induction setups?

[danhr]

3" would be ideal imho. Backpressure is just an urban myth. I have discussed it with many mainstream shops, and they all the same. I am sure someone will chime in saying the opposite though.

Why are you thinking of a 2.5 instead of a 3? if you want a 2.5, I would just stick with the stock exhaust with a better muffler, imho.

[Mindz]

Well, I have a 3" catted midpipe that I can go one of three ways.

Custom 3" mandrel exhaust,
3" catback exhaust system
diverters (3" inlet, 2.5" outlet and keep stock exhaust).

If 3" is ideal, than it would narrow the choice down to 2 instead of 3. All three prices are the same give or take $150.

[danhr]

so for an extra $150 you can have a full 3" exhaust over a 2.5" exhaust?

c'mon

[speedster]

Mindz -

3" exhaust necessary? Ha, that's like asking "Do I really NEED 517 RWHP?"

Sometimes they go with 2.5" to keep the heat and velocity up but you have FI. Go for the 3", you won't regret it. Simpler. No reducers. Able to support any future temptation for more power...

Plus they sound great !!

[Mindz]

Originally Posted by danhr

so for an extra $150 you can have a full 3" exhaust over a 2.5" exhaust?

c'mon

extra 150 I could have 3" straight out exhaust (almost open headers) and at the flick of a switch, have a nice quiet cruising mellow note so I don't get pulled over leaving work in SF at 2 am when the bars close (I work nights).

[danhr]

electric cut outs are GAY

[urr2slo]

hey jay, as you know i worked with magnaflow very closely on this, if your making more the 500 you will make more with a 3", but to really take advantage of it you need to tune for it. once you start doing big mods, like you have, tuning is a very critical part of it. with the package your running i would go 3" and then straight to your tuner to maximize your potential.

[Mindz]

I plan on it. Just need to figure out which setup to get. The 3" comp series caught my eye, but I don't know if it'll be too loud. the 2.5 street series with LT that I heard today in person was nice and quiet.

[SummoneR]

Say bye bye to your version of "Bone Stock" LOL

BTW what little I know 3" definitely!!!

[urr2slo]

Originally Posted by Mindz

I plan on it. Just need to figure out which setup to get. The 3" comp series caught my eye, but I don't know if it'll be too loud. the 2.5 street series with LT that I heard today in person was nice and quiet.

you've heard mine, is it to loud? i have magnaflow's 3" comp series, with the dynatech l/t's. i like the way mine sounds, it's only really loud i bury my foot in it.

[AlSuwaidi]

from what i read all over it seems that 3" is when you get up to the high hp numbers.. basically FI...

so i would go for three.. 150 is not gonna harm you much in the long term

[Jontall]

Kooks has a super nice 3" stainless exhaust.

[Mindz]

Originally Posted by urr2slo

you've heard mine, is it to loud? i have magnaflow's 3" comp series, with the dynatech l/t's. i like the way mine sounds, it's only really loud i bury my foot in it.

Haven't heard your car while it's running

Originally Posted by AlSuwaidi

from what i read all over it seems that 3" is when you get up to the high hp numbers.. basically FI...

so i would go for three.. 150 is not gonna harm you much in the long term

The 150 more is for the diverters. the 3" is the cheaper.