Engine CFM

[John Dammeyer]

>Date: Wed, 1 Sep 1999 15:11:20 -0700 (PDT)
>From: "Jon V." <jon at valesh.com>
[snip]
>Yeah, I was thinking about it two ways... assuming that my Internet
>calculator skills are sufficient to the task, a 2L engine that redlines
at
>6.8-7.2K (about where mine does/would) needs ~23036 CFM to feed it. The
>1300, 12KRPM motocycle engine would need ~26327 CFM (These numbers are
>pulled from the net, and I didn't check the assumptions that went into
>them... just CID, RPM, and (a high) 95%VE), which sounds like it
>is a perfect fit and everything is WONDERFUL and I'm just wishing I
could
>figure out where I'm gonna find a Suzuki without an owner for long
enough
>to... um... anyway... I'm trying to find the parts...


Hi,

These are the types of assumptions that do need checking out, especially
if you are sizing injectors.  A 2L engine is about 121 cubic inches.
for every revolution it has two cylinders that do an intake stroke so it
requires 121 / 2  = 60.5 cubic inches of air per engine revolution.
This works out to 7200 RPM * 60.5 cubic inches per rev = 435600 cubic
inches per minute.  With 12^3 cubic inches in a cubic foot we divide
into the cubic inches per minute to get 435600/1728 = 252 CFM or 15,120
Cubic Feet per Hour.  Quite a different number from ~23036 CFM.

Now just work out how how much 15,120 Cubic Feet weighs and you should
get how many lbs of fuel required per hour at 100% duty cycle assuming
100% VE.

John