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Author Topic: turbo LS exhaust  (Read 2610 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!
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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".


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'88 TII -  Rods/Pistons LS3, Twin G30-770s, MaxxECU Pro/PDM
BMW DCT Swap, Ronin 8.8" IRS

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 😂
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Offline gnx7

Re: turbo LS exhaust
« Reply #3 on: April 11, 2021, 06:23:30 PM »
When my silver turbo FD was reworked for the 88mm T4 turbo the 4" downpipe simply wouldn't fit.  3.5" is on it and makes 1200rwhp+
Even with a 3" downpipe on the previous GTS76 turbo it made 1000rwhp
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'93 FD: 441ci/AllPro LS7 heads/intake en route, T56 Mag, 8.8" IRS, HolleyHP, DavisTechTC 10.32@137mph cats/full exhaust. 165mph 1/2 mile (old LS7)
'93 FD LS9 turbo, T56 Mag, Samberg 8.8" solid axle, 9.35@163mph 197mph 1/2 mile
`69 Chevelle: alum 5.3, GTS76 turbo, ChiseledPerf A/W, T56 Magnum,Ford 35 spline 9".CTS-V interior http://www.norotors.com/index.php?topic=18234.0
old yellar....440rwhp/FD sold but not forgotten: http://www.ponycars.net/scc.htm
I sell new T56 Magnums/McLeod clutch/T56 rebuild kits/Holley EFI/FIC injectors and all BrianTooleyRacing parts.  norcalmotorsport@gmail.com

Offline Exidous

Re: turbo LS exhaust
« Reply #4 on: April 15, 2021, 03:05:06 PM »
I'll parrot the full 3.5". It's plenty.
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94 BB Sleeved gen IV LS7, MS3ProU with TC, RONIN 8.8 and LT's with custom 3.5"single to VAREX muffler.

Offline driftnfb

Re: turbo LS exhaust
« Reply #5 on: April 26, 2021, 08:13:44 PM »
Do you have an FD? What turbo manifolds are you using?

Alex
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1994 Mazda RX-7
LS2, T56, Twin Turbo Comp 6061 Air-cooled Madness, Ronin 8.8
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