brake horse power & others
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I had a question that has been bugging me for awhile about brake horsepower. I can't put in perspective of what it essentially means or looks like. How does it differ from horsepower and what does horsepower mean? how do these differ from torque and what does torque mean? Noob questions i know, but its better to be a seeking information noob then just a noob all in it self.
sorry if its in the wrong thread. i couldn't think of where else it might go and this generally relates to the 350z and any other car.
sorry if its in the wrong thread. i couldn't think of where else it might go and this generally relates to the 350z and any other car.
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Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components such as power steering pump, muffled exhaust system, etc. Brake refers to a device which was used to load an engine and hold it at a desired RPM. During testing, the output torque and rotational speed were measured to determine the brake horsepower. Horsepower was originally measured and calculated by use of the indicator (a James Watt invention of the late 18th century), and later by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake. Although the output delivered to the driving wheels is less than that obtainable at the engine's crankshaft, a chassis dynamometer gives an indication of an engine's 'real world' horsepower after losses in the drive train and gearbox. This gives a reasonably accurate indication of how a wheeled vehicle engine will perform once on the road.
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Horsepower (hp) is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.[1] Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the output of piston engines, turbines, electric motors, and other machinery. The definition of the unit varied between geographical regions. Most countries now use the SI unit watt for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is only permitted as supplementary unit.
Last edited by trodis; 01-25-2012 at 12:56 PM.
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Brake Horsepower (BHP) is measured at the engine. Not to be confused with Rear Wheel Horsepower (RWHP) that is measured at - get ready! - the rear wheels. There is generally a significant loss between the two - anywhere from 20-30%, maybe more. Car manufacturers claims are almost always BHP. When you see claims here, they are generally from a chassis dyno that measures it at the rear wheels.
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Brake Horsepower (BHP) is measured at the engine. Not to be confused with Rear Wheel Horsepower (RWHP) that is measured at - get ready! - the rear wheels. There is generally a significant loss between the two - anywhere from 20-30%, maybe more. Car manufacturers claims are almost always BHP. When you see claims here, they are generally from a chassis dyno that measures it at the rear wheels.
Brake HP is also referred to as crank horsepower, or power at the crank. Sometimes called engine horsepower.
Torque is important in getting the car off the line. Let's say you have 2 identical cars (same chassis, transmission, tires, even the same powerband) but one car has 500whp and 100wtq while the other has 400whp with 300whtq. The car with more torque will get off the line quicker. This example could never happen in real life; it's theoretical.
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Don't forget about FWHP or AWHP. I use "WHP" (wheel horsepower) as a blanket term.
Brake HP is also referred to as crank horsepower, or power at the crank. Sometimes called engine horsepower.
Torque is important in getting the car off the line. Let's say you have 2 identical cars (same chassis, transmission, tires, even the same powerband) but one car has 500whp and 100wtq while the other has 400whp with 300whtq. The car with more torque will get off the line quicker. This example could never happen in real life; it's theoretical.
Brake HP is also referred to as crank horsepower, or power at the crank. Sometimes called engine horsepower.
Torque is important in getting the car off the line. Let's say you have 2 identical cars (same chassis, transmission, tires, even the same powerband) but one car has 500whp and 100wtq while the other has 400whp with 300whtq. The car with more torque will get off the line quicker. This example could never happen in real life; it's theoretical.
I've seen a few earlier 287 HP pull 230 on the dyno, sometimes less. So 30% might be a stretch with a 350 but 20% is probably close. I think dyno's are worthless except for comparisons, but still.
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