Turbo Tech: Calculating Compressor Flow

MatchBot cranks out the compressor mass flow and pressure ratios on the EFR 67mm compressor map. Using MatchBot is a bit iterative, so I had to get the points plotted on the map first and then get the efficiency values off of the map to plug into the inputs section.

Paired with the smallest EFR 6758 turbine, this sucker will spool pretty fast.

MatchBot cranks out Actual Flow Rate pretty damn close to my calculated values. The pressure ratios matches too. The difference is due to the slight differences in intake manifold temperature. It’s nice when the math works out right? About that corrected mass flow equation. We have calculated actual mass flow based on the estimated actual temperatures and pressures. To calculate corrected mass flow to accurately plot on a compressor map, you need to know the reference temperature and pressure the maps were corrected to. We will just say our actual calculated mass flow values are close enough. With my sizing of the EFR 6758, the engine dP is about -15psi (based on my assumptions including exhaust back pressure) which is about as negative as you want to go. Notice that a big wastegate port is required to run low boost on the S2000. This is due to the high VE of the engine, so not much boost is required to make power relatively speaking. So, a ton of wastegate flow is required when a small turbo is paired with an engine with high VE.