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What is horsepower and what does it measure?

What is horsepower in automotive lingo? Horsepower is simply a measurement of mechanical power, or the rate at which work is done. One horsepower equals 33,000 ft-lbs of work per minute. It’s the amount of power necessary to raise 33,000 pounds a distance of one foot in one minute. If you know the torque of your engine (this measurement normally requires a dynamometer), you may use the following equation to calculate its horsepower: rpm x torque Horsepower = 5252 Conversely, if you know the horsepower of your engine at a particular rpm, you may rearrange the above mathematical expression to: Horsepower x 5252 Torque = rpm Plug in your horsepower value at a given rpm, and you will arrive at your car’s torque at that rpm.

What is horsepower: gross vs net ratings

There are two forms of torque and horsepower measurement: Gross and net. The gross figures represent what the engine can do under ideal conditions. The net torque and power, conversely, indicate what the engine is able to do as it’s installed in its vehicle, with all the trappings such as, alternator, fan, air conditioning, power steering, and intake and exhaust systems attached.

1971 and earlier vehicles were typically rated by the gross system of measurement, while 1972 and later vehicles are rated by the net system. There is usually a major discrepancy between the theoretical (gross) and actual (net) figures.

That’s one of the reasons why 1971 and earlier engines tend to have higher horsepower ratings.