# Handy Simple Formulas For Engine Measurements



## Sid327 (Sep 19, 2019)

Kw to HP - x 1.34

PS to HP = x .986 (100ps = 98.6hp)

Nm to Ft/lbs torque = Divide by 1.356

Cylinder capacity = B x B x S x .7854 / 1000 = capacity of one cylinder (then multiply nr of cylinders for total capacity).

HP to TQ = HP x 5252 / rpm (Imperial)

TQ to HP = TQ (lbs/ft) x rpm / 5252 (Imperial)

BMEP = TQ x 2473 / cc (200psi is a yardstick for excellent efficiency for NA engines).

CR = CV+SV / CV

CID to cc = x 16.3871

Note: The old standard for measuring HP is known as *SAE J607* which used ISA conditions of 15°C (59*°*F) 0% relative humidity and a barometric pressure of 1013.2 Mb (Kpa) or 29.92 in-Hg. This is still used in the aviation industry to my knowledge.
There is a newer standard *SAE J1349* which is widely used in the automotive industry now which uses a more realistic 25°C (77°F) with 0% relative humidity and a barometric pressure of 990 Mb (Kpa) or 29.234 in-Hg (for net certified power).

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