Engine Horsepower

Written by Jerry Ratzlaff on 14 January 2016. Posted in Fluid Dynamics

Engine horsepower, abbreviated as EHP, is the estimate of engine horsepower after a quarter mile run using the trap speed.

Engine Horsepower formulas

\(\large{ EHP = W \; \left( \frac{ v }{ 234 } \right) ^3 }\)
\(\large{ EHP = \frac{ W }{ \left( \frac{ ET }{ 5.825 } \right) ^3 } }\)	(elapsed time)
\(\large{ EHP = W \; \left( \frac{ s }{ 234 } \right) ^3 }\)	(trap-speed)
\(\large{ EHP = \frac{ \tau \;\; s \;(RPM) }{ 5252 } }\)	(rotating horsepower)
\(\large{ EHP_{change} = W \; \left( \frac{ v_2 }{ 234 } \right) ^3 \;-\; W \; \left( \frac{ v_1 }{ 234 } \right) ^3 }\)	(determine increase in horsepower)
\(\large{ EHP_{change} = \frac{ W }{ \left( \frac{ ET_2 }{ 5.825 } \right) ^3 } \;-\; \frac{ W }{ \left( \frac{ ET_1 }{ 5.825 } \right) ^3 } }\)	(determine increase in horsepower with ET)

\(\large{EHP}\) = engine horsepower

\(\large{ET}\) = elapsed time (time to finish quarter mile)

\(\large{ET_1}\) = initial elapsed time (time to finish quarter mile)

\(\large{ET_2}\) = final elapsed time (time to finish quarter mile)

\(\large{s}\) = speed

\(\large{ \tau }\) (Greek symbol tau) = torque

\(\large{v}\) = velocity

\(\large{v_1}\) = initial velocity

\(\large{v_2}\) = final velocity

\(\large{W}\) = weight