How to Convert Engine Horsepower to Wheel Horsepower?
2 Answers
Engine horsepower and wheel horsepower are converted as follows: 1 metric horsepower = 75 kilogram-force·meter/second = 735 watts. Below is an introduction to engine horsepower and wheel horsepower: 1. Wheel Horsepower: Wheel horsepower refers to the horsepower value exerted by the tires on the ground when the car is in motion. The engine's output power needs to pass through the clutch, transmission, and drive shaft to reach the car's tires. During this process, there is a loss of power, and the component that affects power the most is the car's transmission. 2. Engine Horsepower: Engine horsepower refers to the rated power of an internal combustion engine. Since engine power is usually expressed in horsepower, when discussing engine displacement, it is often represented in terms of horsepower.
I often encounter this issue when dealing with vehicle performance upgrades. The difference between engine horsepower (crank horsepower) and wheel horsepower depends on drivetrain efficiency, simply put, it's the power loss from the engine to the wheels. Generally, wheel horsepower is about 70% to 85% of crank horsepower, depending on the drivetrain layout—front-wheel drive cars have shorter power paths and higher efficiency, rear-wheel drive cars lose about 5% more due to driveshaft losses, and all-wheel drive systems are more complex and can lose up to 25%. When I help clients with modifications, I’ve found that automatic transmission cars lose 5%-10% more horsepower than manual transmissions. New cars can achieve up to 90% drivetrain efficiency, but after 100,000 kilometers, aging rubber components can drop efficiency to around 75%. Don’t trust those fixed conversion formulas online—I’ve seen two cars with the same 200 horsepower rating differ by 30 hp in actual wheel horsepower measurements. If you want precise data, you’ll need to visit a professional tuning shop and test it on a dynamometer.
