Question about exhaust pipe sizing formula (math)

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Jan 2, 2007 | 04:03 PM

senicalj4579

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Question about exhaust pipe sizing formula (math)

I know exhaust pipe sizing is = PI x R x R = Area x 115 CFM / 2.2 CFM Per HP
but is this the same formula you would use for the header primaries?

Last edited by senicalj4579; Jan 2, 2007 at 04:32 PM.

Jan 3, 2007 | 07:58 AM

senicalj4579

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it must be the math

lol

Jan 3, 2007 | 08:35 AM

Ragtop 99

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I've seen header primaries calculated using a formula that accounts for rpm and displacement to calculate the length and diameter.

Jan 3, 2007 | 11:13 AM

senicalj4579

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Quote:

Originally Posted by Ragtop 99

I've seen header primaries calculated using a formula that accounts for rpm and displacement to calculate the length and diameter.

do you know how the formula goes? or do you just know theres a formula?

Jan 3, 2007 | 11:19 AM

lsx24

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I've seen that formula somewhere too, but I don't know what it is. Fwiw the formula you quoted will calcualte the potential flow rate, but it will not calculate the optimal header dia and length.

Jan 3, 2007 | 12:34 PM

Ragtop 99

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Per a post by J-Rod:

Quote:

The formulas I have are:

Header pipe length (in inches) = ((850*(360-EVO))/RPM – 3
Header diameter (in inches) = ((cylinder. disp. * 16.38 / ((hdr len + 3) * 25))) * 2.1

EVO - Exhaust Valve Opens (gross)

These formulas are from A. Graham Bell’s Performance Tuning in Theory and Practice.
For a street engine, the RPM used should be the peak torque RPM. For a race engine, the peak hp RPM should be used. I find that the peak tq numers to be insanely long. So, I use peak HP.

Other possible links:
http://www.headerdesign.com/login/header.asp

http://www.popularhotrodding.com/en..._exh/index.html

http://www.popularhotrodding.com/en...h/photo_04.html

There is a software called pipemax which I've seen recommended to.