Power
The power of an engine is often described in terms of brake horsepower (BHP), for instance the internal combustion engine of a formula 1 car is capable of producing in excess of 600 BHP. But what actually is BHP?
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Brake Horsepower is the power produced just outside the engine, that is the power produced by the crankshaft before any is lost through the gear box or drive train. This minuses away any losses due to friction. To put 1 BHP into perspective, we need to understand the idea of torque.
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"Horsepower sells cars, torque wins races"
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Torque is simply a measure of the force that causes an object to rotate about an axis.
Imagine a builder’s wrench attached to bolt, the torque is the force the builder requires to unscrew it. If this wrench is two feet long, and the builder pushes it with 20 pounds of pressure, then he is applying 100 pound-feet of torque.
1 horsepower is the amount of power it takes to perform 33,000 foot-pounds of work in one minute. [1]
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Torque causes the vehicle to accelerate and therefore is of vital importance at lower speed. Horsepower then takes over and torque is reduced. This is what the quote above is referring to.
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So now we have developed an idea of torque, we can go back and relate it to BHP. The equation that combines torque, BHP and RPM is:
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Formula 1 limits the RPM produced by the engine to 15,000 RPM although they actually rarely reach 12,000. So how does the power unit create the additional BHP seen on the track? [2]
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The secret is in the Energy Recovery System.
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A Simple Engine
Energy Recovery System