Best Exhaust Size?
Thread Starter
Teching In
Joined: Nov 2003
Posts: 19
Likes: 0
From: Winterpeg, Manisnowba, Canada
Best Exhaust Size? What would be the optimal exhaust pipe size for a stock eng.? How does one figure out if there even is a best size. Does the bigger is better rule apply here? Assume a free flowing exhaust, (no resriction to airflow) would a smaller pipe create more backpressure or is backpressure soley caused by flow restriction? How do I figure out total exhaust flow in CFM? Is it cubic inches of engine * (rpm / two) = exhaust cfm?
If that formula is correct, (If I'm wrong please tell me) then using redline rpm shouldn't you be able to figure out theoretical maximum possible flow cfm in exhaust. Knowing this, can't we figure out what flow number we need in our cats and mufflers to avoid restriction? Also knowing total exhaust flom cfm can't we also determind the exhuast pipe size required to avoid restriction?
This post was just a thought that popped into my head, I am NOT basing these theories on any actual information. Any and all corrections are welcome.
If that formula is correct, (If I'm wrong please tell me) then using redline rpm shouldn't you be able to figure out theoretical maximum possible flow cfm in exhaust. Knowing this, can't we figure out what flow number we need in our cats and mufflers to avoid restriction? Also knowing total exhaust flom cfm can't we also determind the exhuast pipe size required to avoid restriction?
This post was just a thought that popped into my head, I am NOT basing these theories on any actual information. Any and all corrections are welcome.
Thread Starter
Teching In
Joined: Nov 2003
Posts: 19
Likes: 0
From: Winterpeg, Manisnowba, Canada
revision A revision to my first post.
1 cubic foot = 1728 cubic inch
1 cubic inch = 0.0005787037 cubic foot
[engine cubic inch * (rpm / 2) / 1728] to get cfm.
So a 350c.i. eng should have about 658cfm (corrected to standard conditions 15*C/52*F @ 29.92 in/hg) exhaust flow, but thats not including the temperature. Exhaust is hundreds of degree's F. so how would I account for thermal expansion?
Has anybody measured actual exhaust flow from their car? Any ideas on stock numbers? I'm just trying to figure out exactly what I need. Would Borla or TEA have information on this? Would they repy to E-mail questions like this?
1 cubic foot = 1728 cubic inch
1 cubic inch = 0.0005787037 cubic foot
[engine cubic inch * (rpm / 2) / 1728] to get cfm.
So a 350c.i. eng should have about 658cfm (corrected to standard conditions 15*C/52*F @ 29.92 in/hg) exhaust flow, but thats not including the temperature. Exhaust is hundreds of degree's F. so how would I account for thermal expansion?
Has anybody measured actual exhaust flow from their car? Any ideas on stock numbers? I'm just trying to figure out exactly what I need. Would Borla or TEA have information on this? Would they repy to E-mail questions like this?
