Charge pipe and down pipe sizing ?
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Charge pipe and down pipe sizing ? How much does a 3" vs 4" down pipe gain or loose?
I'm fabbing my down pipe and wondering if 4" will be a big benefit vs 3" @ my hp goals.
How much does a 2.5" vs 3" charge pipe gain or loose?
I ordered a 2.5" and was worried if it'll be a restriction vs a 3" at 7-800 fwhp
I'm fabbing my down pipe and wondering if 4" will be a big benefit vs 3" @ my hp goals.
How much does a 2.5" vs 3" charge pipe gain or loose?
I ordered a 2.5" and was worried if it'll be a restriction vs a 3" at 7-800 fwhp
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From: Ohio
Either size on either pipe will be fine at 700hp. Go with what's cheapest and most available for you. Honestly with the downpipe I would try to fit a 4" but if fitment is a problem you aren't going to miss your goals with a 3".
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Ok good. That rule will put me right around 4" with the 3" outlet I have. I should be able to fit a 4 incher down there. Would like to run it to the bumper, may need oval to do that, we'll see when I get to that point.
I saw a nice test once, I wish I remember what company put it together, I'll look for it later (was 4 or 5 years ago on bimmerforums).
Anyway, they tested different downpipe sizes on the same car, same turbo, but tuning for each setup, and found that downpipe and subsequent backpressure followed a number of expected trends:
-Ratio of "drive pressure" to "back pressure" was always fairly fixed (ie 10 psi turbine drive with 2 psi back pressure, with 4 psi back pressure they saw 20 psi, etc.)
-Larger downpipes significantly improved spool - even when the exhaust got smaller after mid-length (exhaust cools and shrinks in volume so no real friction increase)
-There were no downsides other than packaging and sound to going bigger - performance ALWAYS got better.
Charge pipe is a completely different story - you get into a spool vs top end debate on too many levels.
Anyway, they tested different downpipe sizes on the same car, same turbo, but tuning for each setup, and found that downpipe and subsequent backpressure followed a number of expected trends:
-Ratio of "drive pressure" to "back pressure" was always fairly fixed (ie 10 psi turbine drive with 2 psi back pressure, with 4 psi back pressure they saw 20 psi, etc.)
-Larger downpipes significantly improved spool - even when the exhaust got smaller after mid-length (exhaust cools and shrinks in volume so no real friction increase)
-There were no downsides other than packaging and sound to going bigger - performance ALWAYS got better.
Charge pipe is a completely different story - you get into a spool vs top end debate on too many levels.
