PTS Flowbench Forum

coulterracn wrote:

Flow = ( CID * RPM * .000978474 * Ve% ) / ( Cylinders * 127.5 )

When i did the math i got 165 cfm for my 3L at 95% ve 7k rpm

When i figure my max power for my engine via this engine dynamic calculator
http://www.turbodriven.com/performancet ... sin=92044&
I get 372cfm for the whole engine, which is 25.77 lb/min of air which is consistent with the power I would expect.(~10lb/min for every 100bhp) That correlates to 62cfm per port which is way off from the equation.



Is the cfm low for the calculator because that math equation is figuring that the engine is only pulling air a partial of the full otto cycle? therefore the engine needs more air potential than an open pipe with constant suction would need?
2.67 * 62cfm= 167cfm






Thanks for the info
Fox

Flash,

The 1.5% difference in the speed of sound at your location will make just that a 1.5% difference or very small. The port speed will be directly tied to port cross sectional area, the higher the VE the larger the cross sectional area. The speed at the SSR is critical if too high the port will be very turbulent, fuel will not want to stay with the air flow. Slow the SSR by making the SSR wider or giving it more vertical room.

Someone commented on not trying for "Pro Stock" ports, if that was to suggest not setting up a port for 120+% VE I agree, if it suggested not trying for a really good port I disagree. There is a lot of work in providing a really good port for a client, regardless the application. The proper port size and flow for a given engine will produce the best power under the curve likely what the customer is paying you for.

Stay tuned,

PFM