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Old 08-25-2006, 03:47 PM   #1
Scooby Newbie
Member#: 93758
Join Date: Aug 2005
Default header project

I'm considering starting a project on building a header. I read several posts that say piping 2.25" diameter is the best and anything higher like 2.5" you tend to lose low end torque because a reduction in back pressure. What is the optimal back pressure to have to maximize torque without bogging the engine down? Anyone have any ideas on how you would measure this?

I'm considering making this a full blown project of an optimized header for one of my mechanical engineering design classes, analyze with cfd programs current designs and an optimized design and build and test a proto to increase major low end torque before 3500 rpms on an NA impreza motor. Any ideas are welcomed.
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Old 08-31-2006, 12:41 PM   #2
Back Road Runner
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Member#: 60082
Join Date: Apr 2004
Chapter/Region: MWSOC
Location: Minnesota
2004 Forester STI



The article covers the entire exaust system, but there's also a handy chart for optimized header pipe diameters based off flow rate, basically tuning for a certain rpm range but near optimum scaveging for apparently a 4000rpm wide band, so the article says.
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