gaz097 Bronze Donating Members 1,751 Member For: 13y 3m 28d Posted 03/08/19 02:55 AM Author Share Posted 03/08/19 02:55 AM Will a 3.5" be an improvement? Or do I need 4"? Link to comment Share on other sites More sharing options...
camo86T Silver Donating Members 1,810 Member For: 10y 9m 6d Gender: Male Location: SW Sydney Posted 03/08/19 04:59 AM Share Posted 03/08/19 04:59 AM (edited) Twin 2.5" has similar cross sectional area to 3.5", obviously less friction in the single but I doubt there will be your money's worth of an improvement. If you're making the move from twins to drone city, make it worthwhile and go 4" imho Edit My 2c only, interested in what the eggspurts think Edited 03/08/19 05:02 AM by camo86T 1 Link to comment Share on other sites More sharing options...
HI PSI Member 1,586 Member For: 18y 5m 24d Gender: Male Location: Central Queensland Posted 03/08/19 05:58 AM Share Posted 03/08/19 05:58 AM 3 hours ago, gaz097 said: Will a 3.5" be an improvement? Or do I need 4"? Bigger the exhaust the better. Unlike n/a engines, after exhausts turbo do not require back pressure. The back pressure is between the exhaust wheel and the exhaust valve... There are big gains to be had here.... 1 Link to comment Share on other sites More sharing options...
NA_TURBO Member 532 Member For: 9y 1m 10d Gender: Male Location: Mildura Posted 03/08/19 06:35 AM Share Posted 03/08/19 06:35 AM Twin 2.5" has similar cross sectional area to 3.5", obviously less friction in the single but I doubt there will be your money's worth of an improvement. If you're making the move from twins to drone city, make it worthwhile and go 4" imho Edit My 2c only, interested in what the eggspurts thinkI agree,I don't think the friction difference between twin 2 1/2 and single 3 1/2 would cause enough of a restriction to worry about. Link to comment Share on other sites More sharing options...
eff xr6t Member 569 Member For: 11y 1m 19d Posted 03/08/19 10:56 AM Share Posted 03/08/19 10:56 AM I'd do a simple test before you outlay the money and drop the exhaust at the dump for a test. Imo you will find it won't make a difference. I'd focus on pulling the boost back and find mbt then put boost in till you find the motor starting to choke from the small turbine. You find as the exhaust housing starts to become the restriction that you will have to pull fuel out because the VE will drop off. 1 Link to comment Share on other sites More sharing options...
arronm Dropping a turd Gold Donating Members 9,520 Member For: 17y 22d Gender: Male Location: Perth Posted 03/08/19 11:31 AM Share Posted 03/08/19 11:31 AM True. But this may not be representative if the cat is restrictive. Link to comment Share on other sites More sharing options...
NA_TURBO Member 532 Member For: 9y 1m 10d Gender: Male Location: Mildura Posted 03/08/19 11:33 AM Share Posted 03/08/19 11:33 AM Depends on size of said cat Link to comment Share on other sites More sharing options...
arronm Dropping a turd Gold Donating Members 9,520 Member For: 17y 22d Gender: Male Location: Perth Posted 03/08/19 03:08 PM Share Posted 03/08/19 03:08 PM And then replace the cat to see if it is a restriction. This is what I meant Link to comment Share on other sites More sharing options...
bjc Donating Members 2,823 Member For: 21y 2m 14d Gender: Male Location: Townsville Posted 04/08/19 01:56 AM Share Posted 04/08/19 01:56 AM Surely Gazza doesn't use a cat!? He'd do what we all do and for a hundy swap with a piece of straight through pipe with flanges so it can be bolted in and out in case of Constable/rta emergency!What auto and stall are you using again mate? 617hp? (460ish kw). 3.5" flows more than twin 2.5"...I'm with the other blokes on going the 4" and get a Varex muffler at the rear for cruising but it is expensive! I'd probably go the side dump method using old school valves for the track or if you're feeling rad...get the largest cheapish wastegates you can get and weld them onto the exhaust, have them open at whatever whatever boost level you want. To each his own though! Effy has a good point also (sorry mate Tapatalk I can't see your username EF XR6?) Link to comment Share on other sites More sharing options...
arronm Dropping a turd Gold Donating Members 9,520 Member For: 17y 22d Gender: Male Location: Perth Posted 04/08/19 02:11 AM Share Posted 04/08/19 02:11 AM Why not use a cat. Its the legal option. Exhausts with cats flow over 600rwkw so why remove it. For these cars to make big power on the least boost you need large intake, exhaust , inter-cooler and turbo. The bigger the better, NO restrictions. 1 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now