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How to decide what size DP?

1K views 16 replies 5 participants last post by  97stanger97 
#1 ·
Ive been trying to research online but can't really find much. Is there a specific formula or anything I should be considering when deciding what size DP to run? Obviously every car is different, but it seems like most people just run a certain size and end up changing it down the road and seeing how the car responds. My build is a built 2v 4.6, 10:1, TF 38 cc heads with MHS stage 3 turbo cams, edelbrock manifold, and E85. Planning on the turbo setup to consis of a PTE 7675 CEA and CG Fab hot side. The hot side comes standard with a 3" DP, and I will most likely just run open DP. Does anybody have any thoughts if the 3" would be good enough or should I look to be going bigger? Goals for the car are 800+ through an auto.
 
#2 ·
IMO, For "only" 800hp with your combo I don't think it's going to matter a whole lot whether you go 3" or 4" if you're running open DP. A bunch of people making well over that with a 3" so I would run whatever fits. Where do you plan on dumping the exhaust?

ks
 
#4 ·
Watch local rules if you want to race heads up. Around here they ban front exits and sometimes require exhaust to the back axle or behind driver.
 
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#6 ·
Since the CEA 7675 has a 3" outlet, would there be any benefit to going with a 3.5" or 4", or would it be most efficient to stick with the 3" to match the outlet?
 
#8 ·
I had horrible back pressure issues with 3 inch down pipe. I had to buy a boost controller that could handle duty cycle to keep the boost from tailing off. Went to 4" off the turbo and all my problems went away.

This is my current setup. I am running custom Lunati turbo cams... 225/229 at .050, .494/.496 Lift, Cut 115 LSA With A 105 ICL

Cold Side With Mishimoto R Line Intercooler, Garrett GT4094R Ball Bearing Turbo 1.06 A/R With Tial "Q" BOV & Dual F35 Wastegates, Swaintech Coating On Hotside Piping & Turbo Hotside Housing,

707 HP on 13 psi.

Good luck with your build.
 
#9 ·
Thanks for the info man. I'm getting complete different answers as to which size to go with, but at the end of the day it's not a difficult swap or expensive change so if its something I have to play around with it's not the end of the world. Just would have liked to address the correct parts up front. If the outlet of the turbo is 3", how would say a 4" provide any different benefit than a 3"?
 
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