Calculators

NOTE:  The calculator links below will display Microsoft Excel workbooks. You must have Excel installed on your computer to view and use these calculators.

Forced Induction Calculators (Excel)

Fuel Injector Calculators (Excel)

Tire & Drivetrain Calculators (Excel)

TECH TIP:  Projecting your power increase per pound of boost is perfectly straightforward. I don't understand why people insist on making something mystical out of the process. Atmospheric pressure at sea level is 14.7 psi, so this would be the theoretical intake air pressure at WOT for a naturally aspirated engine at sea level. Adding one psi of boost increases the intake air density by a approximately 6.8%, or 100 x (1 psi / 14.7 psi), so the the percentage increase of intake air pressure resulting from 'D' psi of boost, where D is a target boost level, is as follows:

Percent intake air density increase = 100 x (D / 14.7)

For example, if we observe 9 psi of boost pressure in the intake manifold, the intake air pressure has been increased by the following:

Intake air density increase = 100 x (9 / 14.7), or 61.22%

Now, given a corresponding increase in fuel delivery to maintain the A/F ratio, we can expect to make a theoretical maximum of 61.22% more power, minus pumping losses and parasitic drag. Most twin-screw setups are about 78% efficient, so our expected net power increase becomes 0.78 x 61.22%, or 47.8%. For example, if we were making 300 RWHP N/A, we could expect to make somewhere around the following power after introducing 9 psi of twin-screwed boost:

Estimated pwr @ 9 psi = 300 + (0.78 x 300 x 9 / 14.7) = 300 + 143.27 = 443.27 RWHP

Granted, this power increase is purely theoretical, and various factors can introduce reductions to the calculated value. But it's almost exactly the power increase that many, including myself, have observed, so it's a fairly reliable rule-of-thumb calculation. Please note that the same 6.8% gain per psi does NOT apply when adjusting boost from one level to another, for example when increasing your boost level from 9 psi to 12 psi. The 6.8% constant is derived from ATMOSPHERIC PRESSURE at sea level, so the engine's naturally aspirated power must always be used as the baseline when calculating projected power increases. Always work off that baseline.