Acceleration

Acceleration is the process of changing the rate of velocity or movement. This is the result of available power from the engine. Usually, the bigger the engine, the power it makes. However, a turbo charged or supercharged (forced induction) engine provides an exception to the rule. When air is forced into an engine using a turbo/supercharger it can produce more power and improved acceleration with a smaller engine.

Whenever you hear someone mention horsepower the first thing that usually comes to mind are cars; fast cars with extreme torque, muscle cars with lots of power, and vehicles capable of extreme speed. But why is horsepower so important? James Watt, a famous 19th century engineer, created the term "horsepower" in 1782 as he improved the power of the steam engine. While watching horses haul coal out of a coal mine he came up with the idea of defining the power exerted by these animals, thus the term "horsepower" was born.

He calculated that a normal horse attached to a mill that ground corn or cut wood walked in a circle that was 24 feet in diameter. He then calculated that the horse pulled with a force of 180 pounds. Watt noticed the horse could make 144 trips around this circle in an hour. That is 2.4 trips per minute. Using these numbers he calculated that the horse traveled about 180.96 foot per minute then rounded up and came up with 181 foot per minute. He then multiplied the 181 foot per minute by 180 pounds of force the horse exerted and came up with the number 32,580 foot pounds per minute then rounded up again to the number 33,000 foot pounds per minute. This number is equal to one horsepower.

Mr. Watt used his new term to rate the power of the steam engine. Since most people were unfamiliar with the steam engine he had to come up with a comparison measurement that the farmer of the day would understand. As with any measurement there are different variations and different methods of measuring horsepower or hp. The normal measurement of horsepower is called mechanical horsepower.