February 28, 2021, 02:36:22 PM

Author Topic: turbo LS exhaust  (Read 113 times)

Offline bymuhh228

turbo LS exhaust
« on: February 22, 2021, 06:00:26 PM »
Coming up to a point in my build where I need to finish running my exhaust to the rear of the car and I cant decide what route to go with. I have a stock cube ls2 with a 7675 that i plan to run about 15 psi on. I know with turbo setups that bigger is better for exhaust but the outlet on my turbo is 3'' and I am curious if running a full 3'' exhaust would be suffice for the mid 700hp range or if it would cause to much back pressure. I have my 3'' down pipe currently ran to about where the firewall is and cant decide if i should step it up to 3 1/2 at the firewall and run that all the way out or just buy a 3'' cat back and tie into it. I have read about a few builds utilizing a single 3'' and making good numbers but would like some more input for clarity. Also if anyone has a 3 1/2 inch cat back i would be interested in buying it. Thanks!

Offline shainiac

Re: turbo LS exhaust
« Reply #1 on: February 22, 2021, 06:14:12 PM »
Stepping up to a 3.5" catback would definitely help, but the biggest benefit would be to transition up to 3.5" directly off of the turbo and run a full 3.5". Having a large downpipe right off the v-band will make the biggest improvement performance, and help it spool faster as well.
A full 3" on a turbo 6.0L is just too IMO. I have a very quiet 3.5" exhaust on my turbo FC and had no issues making over 700whp.

Here's a good video showing the differences in downpipe size on a turbo LS on the dyno. The 3.5" had most of the benefits of the 4".


'88 TII -  SBE 5.3L, Twin EFR 6758s, T56 Magnum, Ronin 8.8" IRS, MS3Pro Ultimate
716whp/662wtq @1.3bar

Offline bymuhh228

Re: turbo LS exhaust
« Reply #2 on: February 22, 2021, 09:46:39 PM »
Appreciate the input! I had watched that video and it is what made me consider changing my set up. Originally i had it 3-4 right off the turbo but running a 4 down pipe under the passenger manifold was physically to big for my setup. Sucks cause i have a bunch of nice 3 and 4 ss tubing and mandrel bends but i will just buy some 3.5 inch stuff and hopefully 3rd times a charm 😂