How is horsepower in a car measured?

The horsepower of a car is typically measured using a dynamometer. A dynamometer is a device that measures the torque and speed produced by a rotating shaft. In the context of measuring car horsepower, the dynamometer is connected to the car's engine or driveline, and the car is put through a series of tests to measure its torque and speed at various engine speeds.

The basic principle of measuring horsepower with a dynamometer involves using the following formula:

Horsepower = (Torque × RPM) / 5,252

where:

- Horsepower is the measure of power output in horsepower (hp)

- Torque is the twisting force produced by the engine in pound-feet (lb-ft)

- RPM (Revolutions Per Minute) is the engine speed in revolutions per minute

To perform a dynamometer test, the car is typically secured to the dynamometer's rollers or sensors. The dynamometer then simulates different driving conditions, such as acceleration, steady-state cruising, and inclines, to capture data points across the entire engine speed range. The dynamometer measures the torque and speed produced by the engine or driveline, and calculates the horsepower using the formula above.

It's important to note that there are different types of dynamometers, and the specific methods and equipment used to measure horsepower may vary depending on the type of dynamometer and the purpose of the test. Dyno testing can be performed on various types of vehicles, including cars, trucks, motorcycles, and even engines on a test stand.