to quote Mr. Garrison of South Park, "there's no such thing as a stupid
question, just stupid people".... ;-)
just kidding... really.... I just love that show... and it is a good
question... it also depends on whether you are talking the scientific
definition, or the slang definition...
Scientific: don't think of them as different things... horsepower is just a
measurement of how much work that torque can do...
If you can have 1000 Lbs/Ft of Torque, but at 0 RPM (just a shaft trying to
turn, but held fast by something).. and it does 0 work... nothing moves, so
no work is done... if you put that same 1000 Lbs/Ft of torque at 2000 RPM,
and you get....380 HP! the formula is simply HP=(torque*RPM)/5252. so by
definition, HP is always equal to torque at 5252 RPM... and move the same
torque to a higher RPM, and the HP increases... think of gearing... you can
use gears to get that higher RPM back down to 2000 RPM, and the torque will
be multiplied by the gearing... so if you had that 1000 Lbs/Ft at 4000 RPM,
you'd have ~ 760 HP... put that through 2:1 gearing, and you'd get 2000
Lbs/Ft at 2000 RPM... also 760 HP.
Slang:
Torque refers to lower RPM power, while HP is High RPM power... the figures
that Dodge releases, for example... just for an example, let's look at the
V10:
version torque HP
Ram 450@2800 RPM 310@4000 RPM
Viper 490@3700 RPM 450@5200 RPM
we would refer to the truck engine as a torque monster, while the Viper V10
is a Horsepower monster... but take a look at the figures on a GTSR... the
HP peak is closer to 7000 RPM!
The truck V10 starts making more than 400Lbs/Ft at 1000 RPM!... and the
Viper V10 peaks much higher... I don't know what the torque is @ 1000
RPM, but I bet it's alot lower..
The 2 different engines are the same displacement, but the torque band
(where the engine makes the most torque) is moved up in the RPM range...
this is accomplished through tuning of the airflow... intake, exhaust, valve
timing... generally, if you lengthen and narrow the intake and exhaust path,
and shorten the valve open time (and overlap)... you move the torque down in
the RPM range... conversely, if you widen and shorten the intake and exhaust
path, and lengthen the time the valves are open, the torque moves up in the
RPM range... increasing HP...
Gary Shook
>Got a quick question. First, remember, there is no such thing as a stupid
>question, so be nice! Can someone please explain the difference between
>Torque and Horsepower to me and what drivetrain qualities effect both??
>This is something I've never really understood. (OK OK go ahead, call me
>stupid!)
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