Inliners International Forums General Discussion Hi Performance Suggested head flow

Guys:

Can anyone point me to a formula that predicts (or more correctly, suggests) what intake and exhaust flow should optimally be to support a cylinder of "x" cubic inches at "y" RPM?

For example, what approximate intake and exhaust CFM flow would you need to achieve, given an inline 6 cylinder of 300 cubic inches (or 50 cubic inches per cylinder) operating at (say) 6500 RPM - obviously NOT a street motor?

Is there a general formula that approximates this? I'm guessing you also need cam specifics. And how does VE (volumetric effeciency) play into the calculation? Do you provide VE as an assumed value or is it a derivative of the calculation?

Thanks for any direction you can give.

Russ

Russ, an engine of this type you are describing should do well with about 1 CFM per cubic inch(300 CFM) on the intake ports. But even if you were in the 280-ish CFM range, that would still be good.

CNC-Dude:

Thanks for the response. My gut was telling me about the same thing. Did you come to this by years of experience or did you have some reference material at your disposal?

I've been trying to come up with a (relatively) simple computation that will get me in the ball park for any given cylinder size and RPM range. So far, I'm missing something because the answers I get are either nowhere near enough or way too much flow. Probably some dumb computational error when converting units of measure (either time or volumn).

But at least you have confirmed a target CFM range so I will make another stab at a formula, knowing approximately the answer it should provide.

Thanks again.

Russ

I like to use: http://www.wallaceracing.com/Calculators.htm

There's enough here to take up a lot of time and answer a lot of questions.

Arr

Armond:

Thanks for the "heads up" on the Wallace Racing web site. I'll sure spend some time over there and see what I can gleen.

Russ

Armond:

I poked around on the Wallace Racing (Caclulator) web site and it has just about everything you'd want - including just the head flow calculator I was interested in. I'm sure I'll be back to that site from time to time. Thanks again for the help.

CNC-Dude:

The Wallace Racing calculator estimates just shy of 280 cfm for the example I used in my original post. Good call on your part!

Russ

Russ, I kinda' have a more unique approach that I learned from Headrick, but im glad to see it is sorta' confirmed by more advanced methods :D.