wanna play with the math?
(CID)x(RPM)/3456 will get you the cfm needs of your engine at a given rpm at 100% volumetric efficiency. So take your cubes, 305, multiply that by the rpm you want to run at, devide by 3456 and you have the cfm needs of your engine. So for 4500 rpm it would look like this- 305x4500/3456=398(rounded)
To get a little more precise I have heard some suggest modifying that slightly to this-(CID)x(RPM)x(V.E)/3456
V.E. standing for volumetric efficiency, in a street or lightly modified engine use 0.9, for a high performance or racing engine use 1.1. Makes a huge difference, using the same rpm and a v.e. of 0.9 you now get 357 and a v.e of 1.1 now gets you 436
Last edited by LupinusPectus; 11-03-2007 at 08:34 AM.