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Wheel Horsepower Formula:
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Crank Horsepower (CHP) refers to the power produced by the engine at the crankshaft, while Wheel Horsepower (WHP) is the actual power that reaches the wheels after accounting for drivetrain losses. WHP represents the true performance power available for acceleration and speed.
The calculator uses the Wheel Horsepower formula:
Where:
Explanation: The drivetrain efficiency accounts for power losses through the transmission, driveshaft, differential, and other components between the engine and wheels.
Details: Understanding the difference between crank and wheel horsepower is crucial for vehicle performance evaluation, tuning modifications, and accurate power comparisons between different vehicles and drivetrain configurations.
Tips: Enter crank horsepower in hp and select appropriate drivetrain efficiency (0.85 for FWD, 0.87 for RWD, 0.90 for AWD typically). All values must be valid (CHP > 0, efficiency between 0.85-0.95).
Q1: Why is there a difference between CHP and WHP?
A: Power is lost through friction and mechanical inefficiencies in the transmission, driveshaft, differential, and wheel bearings before reaching the wheels.
Q2: What are typical drivetrain efficiency values?
A: Front-wheel drive: 85-87%, Rear-wheel drive: 87-89%, All-wheel drive: 90-95% depending on vehicle design and condition.
Q3: How is WHP measured?
A: WHP is typically measured using a dynamometer (dyno) that measures torque and rotational speed at the wheels, then calculates horsepower.
Q4: Can drivetrain efficiency be improved?
A: Yes, through lighter components, better lubricants, reduced friction bearings, and proper maintenance of transmission and differential fluids.
Q5: Why do manufacturers quote CHP instead of WHP?
A: CHP represents the engine's maximum potential and provides consistent comparison between different engines, while WHP varies based on drivetrain configuration.