Engine Horsepower

Written by Jerry Ratzlaff on . 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)

Where:

 Units English Metric
\(\large{EHP}\) = engine horsepower \(\large{\frac{lbf-ft}{sec}}\) \(\large{\frac{Btu}{s}}\)
\(\large{ET}\) = elapsed time (time to finish quarter mile) \(\large{sec}\) \(\large{s}\)
\(\large{ET_1}\) = initial elapsed time (time to finish quarter mile) \(\large{sec}\) \(\large{s}\)
\(\large{ET_2}\) = final elapsed time (time to finish quarter mile) \(\large{sec}\) \(\large{s}\)
\(\large{s}\) = speed \(\large{\frac{ft}{sec}}\)   \(\large{\frac{m}{s}}\)
\(\large{ \tau }\)  (Greek symbol tau) = torque \(\large{lbf-ft}\)   \(\large{N-m}\)
\(\large{v}\) = velocity \(\large{\frac{ft}{sec}}\)   \(\large{\frac{m}{s}}\)
\(\large{v_1}\) = initial velocity \(\large{\frac{ft}{sec}}\)    \(\large{\frac{m}{s}}\)
\(\large{v_2}\) = final velocity \(\large{\frac{ft}{sec}}\)  \(\large{\frac{m}{s}}\)

 

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Tags: Power Equations Horsepower Equations