Turbo Size Calculator

A compressor map is plotted against two things: air mass flow in pounds per minute and the pressure ratio across the compressor, and sizing a turbo means finding the point your engine asks for. Enter displacement, peak rpm, volumetric efficiency and target boost with the ambient conditions, and this returns the mass flow, the pressure ratio, the compressor discharge and post-intercooler charge temperatures and the flow corrected to the map reference conditions. A second action goes the other way, turning a horsepower target and your assumed BSFC and air to fuel ratio into the airflow and the boost that would take. This gives the flow requirement and not a part number, because every compressor map belongs to one specific wheel and housing and there is no map data in here.

Calculator Type
Displacement Units
Altitude Measured In
Only the altitude box follows this. Pressures stay in psi and airflow in lb per minute, because that is how every compressor map is drawn.
Temperatures In
Only the temperature boxes follow this. Pressures stay in psi and airflow in lb per minute, because that is how every compressor map is drawn.
How full the cylinders get. 85 to 95 for most modern four valve engines.
The air the compressor is drawing. Left blank it takes 77 deg F.
Read off the efficiency island your point lands in. 70 to 76 is typical.
How much of the heat the compressor added is taken back out. 0 for no intercooler.
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Displacement Units
Temperatures In
Only the temperature boxes follow this. Pressures stay in psi and airflow in lb per minute, because that is how every compressor map is drawn.
Altitude Measured In
Only the altitude box follows this. Pressures stay in psi and airflow in lb per minute, because that is how every compressor map is drawn.
Around 11.5 to 12.5 for a boosted petrol engine at full load.
0.50 to 0.60 for a boosted petrol engine.
After the intercooler. 120 to 150 deg F is usual on a street car, and a blank box takes 130.
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