downpipe/ exhaust size?
03-27-2012, 11:09 PM
#1
Staging Lane
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downpipe/ exhaust size? Trying to finish up my 408ci s475 build and I need some input on the downpipes and exhausts size. I have 2.5" crossover pipes to a t6 s475 but I currently have a 3" downpipe. I have a base tune and have been driving the car some to work all the bugs out before the dyno tune and the car is really slow to build boost. Although I need to check for boost leaks and a good tune will help with spool I am afraid that the 3" downpipe is restrictive. Any input?
03-28-2012, 07:37 AM
#4
An idea.... Before I changed the exhaust, I'd get the tune done. Slow spool could be many things, all the way from the tune to the converter. [Assuming this is an auto.]
A bung below the turbo flange would be a good idea. That way U can check back psi when doing the dyno tests. That infor could help determine the need for a bigger dp.
FWIW, I run a 3" DP on my GN... Made 840FW, thru a pair of Dynomax turbos, out the back..
[But, that was only a v-sicks...]
A bung below the turbo flange would be a good idea. That way U can check back psi when doing the dyno tests. That infor could help determine the need for a bigger dp.
FWIW, I run a 3" DP on my GN... Made 840FW, thru a pair of Dynomax turbos, out the back..
[But, that was only a v-sicks...]
03-28-2012, 09:14 AM
#5
you will see a noticeable restriction as the power rises
on my car above around 11psi the power difference gets substaintial when i have the cutout open or closed
the exhaust is similar to yours and the cutout comes nearly directly off the turbine discharge
its not to say you couldnt make a buttload of power, just not as much as it would
on my car above around 11psi the power difference gets substaintial when i have the cutout open or closed
the exhaust is similar to yours and the cutout comes nearly directly off the turbine discharge
its not to say you couldnt make a buttload of power, just not as much as it would
Last edited by rotary1307cc; 03-28-2012 at 09:19 AM.
03-28-2012, 10:20 AM
#6
Staging Lane
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Thanks guys, I have all the hot side wrapped to help with spool too and I will check for boost leaks but I think the tune is the key. I plan on going to a 4" downpipe when I get my k member
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03-28-2012, 11:08 AM
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Or even worst, lift a head due to high back pressure. They say to try and stay within the size of the outlet within a inch. Cause the turbo was designed to flow a certain amount of air of the outlet size.
My bmr turbo k is a pain. Hard to fit a 4" pipe through the location they designed for the dp, due to the flange on the truck mani being right there. Had to run a sharp 90 of the collector for my crossover and the 4" do still hardly fits.
My bmr turbo k is a pain. Hard to fit a 4" pipe through the location they designed for the dp, due to the flange on the truck mani being right there. Had to run a sharp 90 of the collector for my crossover and the 4" do still hardly fits.
