Horsepower and the work ratings it can produce.

One horsepower will produce a fluid flow of 1 Gallon Per Minute (GPM) @ 1,500 Pounds Per Square Inch (PSI). back pressure.

An electrical conversion in an electric motor is said to be true horsepower and is base for calculations.

One horsepower will produce a current flow of 746 Watts and it takes 746 Watts in electrical current flow (Amperes or I in electrical formulation) to produce one horsepower of work.

One horsepower is equal to a person lifting 550 pounds for one second. An engine produces two things, work potential and heat. In example a person would have to hold over their heads a weight to determine their horsepower and it's a linear equation. Half of 550 is 275 so that would be 1/2 horsepower, half of the 275 psi would be 137.5 or 1/4 horsepower.

Work has two factors, pressure and time - psi per second (psi/sec). An engine needs to produce it's rated horsepower consistently and steadily so the production of work in time should be a constant.

One horsepower for one second would require approximately 179 calories for a person. Work completed from an engine then becomes a division of GPM - PSI - Time and subtracted is the heat developed and dissipated through conduction.

At mechanics basic and fundamental goal of taking a fuel or animal or human and translating it's motion into a useable force for others is to simply translate horsepower into motion. The more work load in pounds per square inch the more horsepower is needed and dependent on the time constraints applied to a process.

You can do a specific amount of work like move a bail of hay upward to a height of 50 feet in 50 seconds with less horsepower than lifting it 100 feet in 50 seconds. So three factors are there weight, distance, and time. The faster you want to do something the more horsepower will need to be translated from the primary mover (engine) to the output device (final drive).

When an internal combustion engine is rated at 100 horsepower at 1,000 RPM (revolutions per minute) the actual horsepower delivered through the final drive may actually be 60 horsepower. The internal combustion engine and it's optimum horsepower rating at any specific RPM is dependent on fuel and octane rating, air to fuel mixture ratio, temperature, lubrication, and any one or all of those contribute to the efficiency factor of the engine. A 100 horsepower engine may only produce 30 horsepower as temperature rises and fuel is low on octane rating.

An electric motor no matter what the horsepower is constant with 746 watts electrical energy volume so the electric motor is basis for all calculations when designing equipment needing torque and horsepower.

For instance in an actuating situation a one horsepower electric motor will lift 550 pounds straight up for a period of time the primary mover (motor) is consuming 746 watts. So the resistance is in weight and the more load the more heat as a by product. Heat can be used to calculate efficiency of an engine. The more heat or thermal energy dissipated the more in-efficient the engine is said to be. Most problems hard to identify usually can be found with an infrared temperature gun, the problem place will be hotter than the rest of any operating system on the device.

For example an internal combustion engine does not have the power or sound like it used to when it was performing well. With a temperature gun you can shoot the spot on each exhaust manifold and tell just what cylinder in the engine is not running as well as the others. The cylinder not running will be cooler than the others. Also in a hydraulic situation if there is a problem with internal leakage that spot will read hotter than the rest of the system. It is easy to find the source of the problem with a temperature gun.

All this knowledge reduced into advanced mechanics reality is this fact, a regular taillight bulb (1157 with both elements working) will draw about 3 amps and depending on the resistance. 3 amps times 12 volts is 36 watts per second. With additional lighting and power amplifiers running as well as auto electrical operating the alternator robs one horsepower for every 746 watts of electrical current consumption. 746 / 12 = 62 amps. which requires fuel to operate each second.

The engines of the past and across the American manufacturers board a 350 / 351 cubic inch carbureted engines rated at 250 horsepower in all applications would get around 10 to 12 miles per gallon turning around 1600 to 2200 RPM. So going 60 miles per hour for one minute would net one mile of travel so the carburetor was flowing at a rate of 5 gallons per hour divided by 60 would be .0833 gallons per minute. A 460 cubic inch engine would get approximately 8 to 10 miles per gallon of gasoline burned. A 1000 cc motorcycle engine or 61 cubic inches would get approximately 32 to 38 miles per gallon. When the V6's came out a 2.2Litre or 123 cubic inches would get around 18 to 24 miles per gallon.

The newer fuel systems are getting way more efficiency compared to the carbureted models prior 1979. Fuel injection and computer controllers have made it possible to get higher fuel mileage per gallon by newer metal running at higher temperatures as well precise amounts of fuel determined by load and speed.