# Turbo Size

spool time in seconds = __turbo compressor wheel size__^{2}

(exhaust psi)(100)

Exhaust psi can be assumed to be 30 psi for the above calculation.

maximum turbo cfm output = __(3.14)(turbo compressor wheel size ÷ 2)__^{2}

3

turbo weight = turbo compressor wheel size + 100

The red sections indicate exhaust passages. Exhaust flows from the outer, red portion of the turbo, through the outer edges of the turbine (the thing with the blades on it), to the red center. The blue indicates intake passages. Air flows from the center of the compressor wheel to the outer edges, speeding up as it goes into the intake system. So what's happening is, the exhaust is spinning the turbine on the exhaust side, which is attached to the compressor wheel on the intake side, so the compressor wheel spins. The compressor wheel on the intake side draws air in faster than it would normally come in and packs it into the cylinder.

## What you do:

Find a balance between **turbo compressor wheel size**, turbo cfm (cubic feet per minute or
ft^{3}/min) and waste gate psi (pounds per square inch or lbs/in^{2}).
Turbo compressor wheel size ranges from 56 - 110 millimeters (mm).

Factors to consider:

spool time in seconds = __turbo compressor wheel size__^{2}

(exhaust psi)(100)

Exhaust psi can be assumed to be 30 psi for the above calculation.

maximum turbo cfm output = __(3.14)(turbo compressor wheel size ÷ 2)__^{2}

3

The HiPerMath equations assume the turbo is spooled up. The equations are:

maximum turbo boost in psi = __(14.7 psi)(maximum turbo cfm output)__

engine cfm

You can assume the cfm will range from 500 - 1500 cfm, depending on your engine specs. Calculating actual engine cfm is massive, so estimating is a good idea.

turbo weight = turbo compressor wheel size + 100

This includes all the piping and an intercooler.Definitions:

cfm = cubic feet per minute = ft

^{3}/min

psi = pounds per square inch = lbs/in

^{2}

rpm = revolutions per minute

mm = millimeter which is one thousandth of a meter.