The math looks good to me, but can You superenginebuilderextraordinaire's check it for errors in theory. To figure VE of an engine in a given application, You'll need to run a test of airflow. To keep it simple, run the engine @ 7k rpm while measuring the amount air drawn into the intake manifold (lb/min or cfm), and the temperature of the air (IAT). Now, bear with me: Density: t1 / t2 = d2 / d1 t1 = temp for air of know density (32* F @ 0.0808 lb/ft^3) in Rankin t2 = IAT (in degrees of Absolute Rankin, F* + 459.67) d1 = density of air for known temperature (0.0808 lb/ft^3 @ 32* F) d2 = Density of intake air charge AVF = Actual Vol. Flow Rate (calculated): Mfa/d2 Mfa = Mass air flow actual (measured) d2 = air density actual (measured) Calculating Theoretical Max Airflow (cfm): TAF = (ED*RPM*VE) / (ES*C) rpm = Operating engine speed TAF = theoretical airflow VE = Vol. Efficiency (100% theoretical ) ED = Engine Displacement (in^3) ES = Engine Stroke (2-stroke = 1 / 4-stroke = 2) C = conversion factor from in^3 to ft^3 (1728) Calculating Volumetric Efficiency: (AVF/TAF)*100 VE = Vol. Efficiency (calculated) AVF = Actual Vol. Flow Rate (calculated) (ft^3/min) TAF = Theoretical Airflow rate (calculated) (ft^3/min) So, we have our equip tested. We come up with: 17.14 lb/min --OR-- 243.8 cfm @ 7000 RPM with our 122 (in^3) engine. The IAT was reading 72* F. Now, do the math: Density: t1 = (32+459.67) = 491.67; t2 = (IAT+459.67) = 531.67; d1 = 0.0808. So: 491.67/531.67*.0808 = 0.0747. AVF: 17.14/.0747 = 229.43. TAF: rpm = 7000; Displacement = 122. So: (122*7000*1)/(2*1728) = 247.11 So, 229.43/247.11 = 0.9284 or 93% VE @ 7000rpm. That about right? Thanks, -Nick
