Question about exhaust pipe sizing formula (math)
01-02-2007, 04:03 PM
#1
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?
but is this the same formula you would use for the header primaries?
Last edited by senicalj4579; 01-02-2007 at 04:32 PM.
lol 
01-03-2007, 11:13 AM
#4
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?
01-03-2007, 11:19 AM
#5
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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.
01-03-2007, 12:34 PM
#6
Per a post by J-Rod:
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.
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.
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.
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.
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01-03-2007, 12:58 PM
#8
Originally Posted by Ragtop 99
Per a post by J-Rod:
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.
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.
very good stuff thanks.
