DIY_EFI Digest V4 #593

[Gary Derian]

The flow capacity of things like throttle bodies or carburetors cannot be
considered a single number.  The number is OK for comparison purposes but
should not be thought of as some kind of limit.  These things will flow more
at a higher pressure drop, less at a lower one.  A gasoline engine consumes
close to 140 cfm for every 100 hp.  A 400 hp engine therefore consumes 560
actual cfm.  A device rated at 650 cfm at 1.5 in. Hg will have a pressure
drop of (560/650)^2*1.5 or 1.1 in. Hg.  If you want less restriction, a 750
rated device will have only 0.84 in. Hg pressure drop on a  400 hp engine.

The flow ratings are merely a point on a curve.

Gary Derian <gderian at oh.verio.com>


> > >Currently my engine only consumes somewhere around 625 cfm max...I
believe
> > >that the BB TBI's flow 670 cfm so I too have thought about a BB
TBI...Holley
> > >makes a SB TBI manifold good for 6000 rpm as well...I'll have to check
it's
> > >height though?