> RPM * engine volume To be horribly pedantic, but hopefully educational, this formula misses a few factors: (1) In a four-stroke internal combustion engine,

> RPM * engine volume To be horribly pedantic, but hopefully educational, this formula misses a few factors: (1) In a four-stroke internal combustion engine, which all car engines are, there is only one exhaust for every TWO engine revolutions. Thus the formula would be: (RPM/2) * engine_volume (2) You’re also assuming the engine is being run at wide-open throttle (gas pedal fully depressed), where the intake pre-compression chamber pressure is equal to atmospheric pressure. In reality, car engines spend very little of their time at wide-open throttle (I hope!), so the average chamber pressure is much lower than atmospheric. See https://en.m.wikipedia.org/wiki/Mass_flow_sensor https://en.m.wikipedia.org/wiki/Mass_flow_sensor (3) Also missing a small ideal gas law “N” factor: there will probably be slightly more molecules in the exhaust combustion products than there were in the input fuel+air. If I had to guess, your RPM * engine_volume estimate is probably higher than reality by one order of magnitude, but not two. Not bad :)