de VIPER » 19 Mai 2008, 23:00
Puterea la roata va fi intotdeauna mai mica decat cea data de motor. E logic, fizic si cum vreti voi.
"The power of an engine may be measured or estimated at several points in the transmission of the power from its generation to its application. A number of names are used for the power developed at various stages in this process, but none is a clear indicator of either the measurement system or definition used.
In general:
Nominal is derived from the size of the engine and the piston speed and is only accurate at a pressure of 7 lbf/in².[5]
Indicated or gross horsepower (theoretical capability of the engine)
minus frictional losses within the engine (bearing drag, rod and crankshaft windage losses, oil film drag, etc.), equals
Brake / net / crankshaft horsepower (power delivered directly to and measured at the engine's crankshaft)
minus frictional losses in the transmission (bearings, gears, oil drag, windage, etc.), equals
Shaft horsepower (power delivered to and measured at the output shaft of the transmission, when present in the system)
minus frictional losses in the universal joint/s, differential, wheel bearings, tire and chain, (if present), equals
Effective, True (thp) or commonly referred to as wheel horsepower (whp)
All the above assumes that no power inflation factors have been applied to any of the readings.
Indicated horsepower
Indicated horsepower (ihp) is the theoretical power of a reciprocating engine if it is completely efficient in converting the energy contained in the expanding gases in the cylinders. It is calculated from the pressures developed in the cylinders, measured by a device called an engine indicator - hence indicated horsepower. It was the figure normally used for steam engines in the 19th century but is misleading because the mechanical efficiency of an engine means that the actual power output may only be 70% to 90% of the indicated horsepower.
Effective horsepower / true horsepower / wheel horsepower
Effective horsepower (ehp), True horsepower (thp) or wheel horsepower (whp) is the power converted to useful work. In the case of a road vehicle this is the power actually turned into forward motion as measured on a chassis dynamometer.
"True hp" is generally 10% to 20% less than the engine's "bhp" ratings due to drivetrain losses.
Wheel horsepower (whp) is the more widely used term for effective horsepower.
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