The Engines
The engine, the main component which
gives the car the power to move, is a very dynamic machine that gives off a
very high amount of work. Cars, trucks, vans and any other type of vehicle has to have an engine for it to be able to move, but the
difference in them is their power called Horsepower. (Horsepower = HP, Watt =
W, 1 HP ~ 746 W) A watt is a unit of energy in the form of Joules per second. Torque,
a twisting motion that causes rotation, is a car’s power output of an engine at
one specific point in time. Torque will usually be in foot-pounds for units. Now
that we covered the very basics of Horsepower and Torque, let’s break it down
to a car’s performance.
Let’s say the new 2014 Corvette String
Ray you just bought (which is very nice) has 460 Horsepower Let’s find out how
much power this engine has.
Take the horsepower and multiply it by
746 Watts. You can simply multiply it or use dimensional analysis.
465HP * (746 W / 1 HP) = 3. 47x10^5
W
(Horsepower)
This powerful Chevy built engine can
produce 3.47x10^5 W. That’s quite a bit of power for such a small car! But it’s
the engineering that went into it that made it the way it works.
For horsepower, it’s calculated by this
expression.
Torque
= (2 * pi * (force * radius) * (RPM) ) / (33,000 ft-lb
/ min)
RPM
= Revolutions Per Minute.
Force
– Usually measured in pounds.
Radius
– the radius from which the force is being applied.
Note:
Force multiplied by the Radius is Torque!
The
33,000 is defined from distance of 100 ft., multiplied by 330 pounds, and all
divided by 1 minute, thus giving us 33,000.
(A vector of Torque)
If you missed it, now
is the time to think that horsepower is a measure of power, and power is
defined by how much work is done over a period of time. Torque, is how much
work is being done. Thus concluding, the higher the horsepower, the faster the
work will get done and the higher the torque, the more work that will be done.
For the final example, diesels usually have more torque and less horsepower.
This is because diesels (think of tractor trailers) need to perform tasks that
high horsepower and low torque couldn’t do. Gas engines, which are non-diesel, are
more for traditional use such as traveling, sports racing, and other non-heavy
lifting duties.
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