rztmartini Posted November 27, 2007 Share Posted November 27, 2007 can someone put in the sticky or somewhere the correct formulas for calculating engine air flow? I trust you guys here a lot more than other random websites, and using thier numbers im not getting consistent answers... one i saw was (displacement*RPM*0.5*Ev)/1728 disp. in ci, Ev=volumetric efficiency, and i dont know where they got the 0.5 or the 1728. another site gave the same, just manipulated the constants: flow=(displacement*RPM*Ev)/3456 oh and btw, would 70% volumetric efficiency be a safe number to use? (who knew getting good information was this hard?! ) and i better not get this stupid smiley!! hahaha nah nah! Quote Link to comment Share on other sites More sharing options...
HLS30RACER Posted November 27, 2007 Share Posted November 27, 2007 First convert the displacement of the engine to cubic feet by dividing the number of cubic inches by1728 (the number of cubic inches in a cubic foot). Ideal flow will be the cu.ft. displacement multiplied by the engine RPM divided by 2 (divided because its a four stroke engine). Now factor in volumetric efficiency to determine actual flow in cubic feet per minute. Displacement(cu.in.) x Engine RPM/2 x Vol. Eff. = CFM 1728 cu in./cu ft. Hope that clarifies the issue a little. Quote Link to comment Share on other sites More sharing options...
zguy36 Posted November 28, 2007 Share Posted November 28, 2007 Check in the downloads section. I have a spreadsheet that will calculate the airflow through your engine based on fuel consumption and air/fuel ratios. With guessing a VE of a certain percentage, you may as well be guessing your airflow. Quote Link to comment Share on other sites More sharing options...
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