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TORQUE AND HORSEPOWER
While torque and horsepower ratings are
common vehicle selling points, many consumers don't fully understand
what the ratings mean or the relationship between the two.
Torque
Most often measured in pound-feet (lb-ft), torque is a
twisting or turning force applied to an object such as wheel, crankshaft
or nut. When tightening a nut with a wrench, for example, the level of
torque placed on the nut is determined by multiplying the force applied
at the end of the wrench by it's length. Applying 100 pounds of force at
the end of a one-foot wrench translates into 100 lb-ft of torque, while
applying the same amount of force at the end of a two-foot wrench
translates into 200 lb-ft of torque.
In automotive applications, torque measures the
engine's ability to perform work. The torque created by the displacement
of the engine cylinders spines the engine crankshaft, and the
transmission applies this torque to the wheels of the vehicle, moving it
forward. The more torque applied to the crankshaft, the more work the
vehicle can do.
Horsepower
While torque measures the turning force produced by a
vehicle's engine and measures the engine's ability to perform work,
horsepower measures how fast the engine can perform the work. Engine
horsepower ratings indicate how much power an engine can produce similar
to how light bulb wattage indicates how much power the bulb will use.
Steam engine inventor James Watt coined the term
"horsepower" in the 18th century for the purpose of comparing steam
engine performance to the better-understood performance of horses, which
were used as the power sources for everything from transportation to
plowing fields and pumping water. It's believed Watt arrived at the
now-standard 33,000 lb-ft per minute (550lb-ft per second) figure for
one horsepower by measuring how quickly a horse turned a gear-driven
mine pump and estimating the amount of force the horse exerted to
perform the work over a given time.
Torque/Horsepower Relationship
Torque and horsepower are related by the following
formula:
Horsepower=Torque x Engine RPM
5252
Plugging various RPM values into the equation provides an idea about the
range of power an engine can produce. Because torque and RPM are divided
by 5252, torque and horsepower are equal when the engine speed is
equivalent to 5252 RPM, while the torque is greater than horsepower
below 5252 RPM and horsepower is greater than torque above 5252 RPM.
The level of horsepower an engine can deliver is directly proportional
to the level of torque generated by the crankshaft, which is directly
proportional to the total displacement capacity of the engine. Because
there is a limitation on the maximum displacement an engine can
generate, there is also a limitation on the amount of torque the engine
can produce, which in turn sets a limit on the engine's maximum
horsepower.
While it's been hotly debated whether torque or horsepower is more
important, it just depends on the driver's priorities. A vehicle with a
higher torque value can perform more work, providing an advantage for
pulling trailers or hauling heavy loads, while a higher horsepower value
performs work faster, making it better suited for highway driving or
racing.
T's Advanced Synthetics
Greg and Marcy Thurman
Your Nationwide
AMSOIL
Authorized Independent
Dealer
Nationwide US Warehouses,
Canada and Palm Harbor, FL
727-798-8552
E-Mail:
greg@tsadvancedsynthetics.com
If you
experience problems or have questions or comments about
our website please email us at
greg@tsadvancedsynthetics.com
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