DIY_EFI Digest V4 #387

[Gary Derian]

It takes 140 cfm of intake to make 100 hp.  Since exhaust is hotter, there
is more.  Lets assume 1100 deg F for exhaust and 70 deg F for intake.
(1100+460)/(70+460) = 2.93.  Therefore every 100 hp has (140*2.93) = 412 cfm
of exhaust.  600 cfm would be only 145 hp.  If the exhaust cools to 800 deg
F by the time it gets to the muffler, 600 cfm would be 180 hp.  The engine
could easily stand 1 or 2 psi backpressure so that muffler is good for more
than the above hp levels.  If you knew the backpressure at 1000 cfm, you
would better know the flow characteristics of the muffler.

Gary Derian <gderian at oh.verio.com>
>
> Date: Tue, 29 Jun 1999 22:58:22 -0500
> From: greg kring <joeao at flash.net>
> Subject: exhaust formulas??
>
> Is there any formulas for figuring exhaust flow by horsepower level? I
> was looking at some Dynoax mufflers and there is one they rate at 0
> backpressure at 600cfm. What horsepower level would that be? It has
> three inch inlets, so it should be fairly decent.
> greg kring
>