Exhaust - Downpipe Diameter - Ford Powerstroke Diesel Forum

 
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post #1 of 7 Old 01-01-2008, 05:25 AM Thread Starter
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Exhaust - Downpipe Diameter

I heard recently that a smaller downpipe will allow the turbo to spool up quicker at lower RPMs - however, a larger downpipe will reduce backpressure. What are your opinions? I'm fixin to spend some Christmas money on a system.
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post #2 of 7 Old 01-01-2008, 05:51 AM
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My 2 cents get a 4 inch downpipe all the way back to the tailpipe so you can lower your egt's if you choose to get a chip or tuner down the road.

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post #3 of 7 Old 01-01-2008, 05:58 AM
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Don't put a smaller one on because if you do add a chip your egt's will go through the roof.

Pat

2000 F250 Carpenter's Union local 2214 LOOKING FOR SIDE JOBS

Mac intake,5" exhaust with6" tip,Zoodad,foil delete, ts chip, WW

96 E350 bad trans mod NO MORE.
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post #4 of 7 Old 01-01-2008, 05:59 AM
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I agree get the 4". For a long time I had the stock exhaust straight piped and put in a 3.5" down pipe. When I switched to the 4" system, I noticed further EGT drop (25-50 degrees at highway speed) and faster turbo spool up.

Chris

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post #5 of 7 Old 01-01-2008, 06:55 PM
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Don't put a smaller one on because if you do add a chip your egt's will go through the roof.
You definatly dont want smaller than stock, but believe it or not a 3" dp (stock) will flow enough for 600rwhp. How do i know??? I made nearly 600rwhp on my obs truck with a 3" dp on fuel only and well over 600 on spray. FWIW I run a 3.5" dp on the superduty, it is the only option with the aftermarket turbo.
post #6 of 7 Old 01-01-2008, 08:53 PM
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I run the same turbo mounting system as Luke however I do not make the power that Luke makes.

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post #7 of 7 Old 01-02-2008, 04:42 AM
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Yeah I know that they will flow enough for big power, but what were the egt's at those levels on a 3" downpipe. Just wondering. I read it as he was going to go smaller than stock, and IMO that would be a mistake.

Pat

2000 F250 Carpenter's Union local 2214 LOOKING FOR SIDE JOBS

Mac intake,5" exhaust with6" tip,Zoodad,foil delete, ts chip, WW

96 E350 bad trans mod NO MORE.
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