When is a 4" exhaust system beneficial
- Thread starter Smutt
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GSRWRC
I am The Stigs fat cousin
When you're running a T51R sized turbo and are after more than 700hp. A 4" exhaust would be very hard to keep quiet too.
Talonfiend
Member
Hmm, why not use a shorter 3" exhaust or a 3.5" exhaust? 4" is extreme you planing on having a 800-900hp daily driver?
trippy
Member
i went from 3"with no cat to 3.5"with a cat with a 3" dump and made an extra 30hp on the same boost to shut it up i run a 3.5"varex muff.just finished my new lobster back 3.5" dump.its a full s/steel system with all joins v clamped and tigged.not cheap but worth it.
trippy
Member
yeah mate.its a custom billet turbo from mr turbo similar to gt35/40.my old dump u can see on onpsi members rides.its a 3" lobster back. i make just over 440hpatw and run 11.04 at 128.3 mph over the 1/4 10's next time.
4" is beneficial for anything over 300kw in my opinion.
I've seen a bunch of Ford Falcons XR6 turbo's see a huge gain with an increase from 3" / 3.5" to 4"....
I've done some testing and have gone from a 3" straight dump to a 3" to the muffler and I lost 50kw's at the wheels. I quickly bypassed the CAT and it gained 20kw's back. Still down 30kw's.....
It is only worth it once you start to make over 300kw's at the wheels imo. Simple rule of thumb.
If you do want a good 3.5 or 4 inch exhaust made, make sure you use a GOOD fabricator!!
The dude who did mine (BJP) made if perfectly and without any clearance issues!!
I've seen a bunch of Ford Falcons XR6 turbo's see a huge gain with an increase from 3" / 3.5" to 4"....
I've done some testing and have gone from a 3" straight dump to a 3" to the muffler and I lost 50kw's at the wheels. I quickly bypassed the CAT and it gained 20kw's back. Still down 30kw's.....
It is only worth it once you start to make over 300kw's at the wheels imo. Simple rule of thumb.
If you do want a good 3.5 or 4 inch exhaust made, make sure you use a GOOD fabricator!!
The dude who did mine (BJP) made if perfectly and without any clearance issues!!
Are we talking removing cat's on a street registered car (highly illegal)
If you see the fine's for running a decat pipe or get done with a punched out cat you'll wish you you just went for a larger i'd sized cat and copped the minor % kw loss.
If you see the fine's for running a decat pipe or get done with a punched out cat you'll wish you you just went for a larger i'd sized cat and copped the minor % kw loss.
Whats the good cats to get these days, baz you found some big ones didn't you?
How can they catch you with a cat that "blew out" anyway?
Isn't it true that they can not remove parts of the car in an inspection at the pits? or can they do it?
An insurance claim might be another matter, if they decide to check to stick you up on a claim.
How can they catch you with a cat that "blew out" anyway?
Isn't it true that they can not remove parts of the car in an inspection at the pits? or can they do it?
An insurance claim might be another matter, if they decide to check to stick you up on a claim.
