Novice question, but I gotta get this figured out:
What exactly is Pounds per feet of torque? Anyone have a physics answer or mechanics answer to this?
I am thinking it's the pounds per feet that the back tires exert on the groun at the given rpms. ???

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2000 Silver Lightning
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This might be more info then you wanted but its very thorough:

Dynamometers use a rotating drum of known mass, spun
by the tested automobile. The drum acceleration and
velocity results in a torque measurement (not HP). HP
is calculated using the equation below, using the
measured torque and RPM (through the test leads
connected to the spark plug wires).

HP = (Torque (ft * lb) x RPM)/5252.
So WHERE does this formula come from? Well, here is
the derivation (if you really do not care, go directly
to my Dyno Curve)

HP = (33,000 * ft * lb)/min
The term horsepower was invented by the engineer James
Watt. Watt lived from 1736 to 1819 and is most famous
for his work on improving the performance of steam
engines. He concluded that the average horse of the
time could lift a 550 pound weight one foot in one
second, thereby performing work at the rate of 550
foot pounds per second, or 33,000 foot pounds per
minute, for an eight hour shift, more or less. He then
published those observations, and stated that 33,000
foot pounds per minute of work was equivalent to the
power of one horse, or, one horsepower. It is that
strange, arbitrary unit of measure that has made its
way down through the centuries and now appears on your
car, your lawn mower, your chain saw and even in some
cases your vacuum cleaner!

Work done during one RPM = (2 * pi * ft * lb *
rev)/min
(remember, there is 2*pi*r distance in a revolution
(circle), and if r=1 ft, then the distance is just
2*pi)
For purposes of this discussion, we need to measure
units of force from rotating objects such as
crankshafts, so we'll use terms which define a
*twisting* force, such as foot pounds of torque. A
foot pound of torque is the twisting force necessary
to support a one pound weight on a weightless
horizontal bar, one foot from the fulcrum.

Now, it's important to understand that nobody on the
planet ever actually measures horsepower from a
running engine. What we actually measure (on a
dynamometer) is torque, expressed in foot pounds (in
the U.S.), and then we *calculate* actual horsepower
by converting the twisting force of torque into the
work units of horsepower.

Visualize that one pound weight we mentioned, one foot
from the fulcrum on its weightless bar. If we rotate
that weight for one full revolution against a one
pound resistance, we have moved it a total of 6.2832
feet (Pi * a two foot circle), and, incidentally, we
have done 6.2832 foot pounds of work.

Now equate HP (which is work over time) with work over
one revolution per minute:

(33,000 * ft * lb)/min = (2 * pi * ft * lb * rev)/min
and then divide 2pi by 33,000 to get:

(ft * lb)/min = (ft * lb * rev)/(5252 * min)

NOW, since HP = (ft * lb)/min
and TQ = ft * lb
and RPM = rev/min

we FINALLY get HP = TQ * RPM/5252

Therefore, when RPM = 5252, HP = TQ (that's why the
curves ALWAYS cross at 5,252 RPM, as shown below).



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Scott