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rallyeNate
05-29-2002, 10:20 PM
please read this post first http://3geez.com/showthread.php?s=&threadid=352

exhaust gas flow should be kept to about MACH 0.22 or 245ft/sec, and your intake airflow should be kept to MACH 0.4 or 450ft/sec. the reason intake airflow is kept to MACH 0.4 is because after that airflow is lost, and drag is increased. the only reason i can offer you is that, this is the best ratio of pressure drop to backpressure. the way to calculate that is by the equation that state, Velocity= airflow rate/area of section
thus if your car flow 500cfm of exhaust would want your exhaust pipes to be 2.5in.
V= [ 500_(ft^3/min)/pi(2.5/2)^2_(in^2) ]*[ 1/60_(min/sec)/1/144_(ft^2/in^2) ]=245_(ft/sec)

to clairify some things
pi=3.14159265359
delta= means change