In this same vein someone once told me this;
“You feel torque from the seat of your pants much more than you feel horsepower.”
The human butt can no more distinguish torque from HP than it can blue light from red light. In simplest terms we are dealing with power or energy, a force that moves you. These forces are expressed in mathematical terms thusly;
1 HP = 33,000 foot-pounds per minute (there’s that over time thing that Bob mentioned)
Or it could be P/hp=[T/(ft lb)][w/(r/min)]
5252
By the way, that 5252 is why nearly all dyno charts show the HP and torque curves crossing at that RPM.
Or it could be 746 watts
Or maybe 2,545 BTUs (British thermal units)
One BTU being equal to 1,055 joules, or 252 gram-calories or 0.252 food calories.
This means that 1 HP is also equal to 2684975 joules, or 63504 gram-calories, or 641.34 food calories
Presumably, a horse producing 1 horsepower would burn about 641 Calories in one hour if it were 100% efficient.
The point is that its energy, a force, what moves you, not some nebulous calculation as others have postulated.
Torque is the force applied to a lever, multiplied by its distance from the lever's fulcrum in our case a theoretical lever and a rotating fulcrum, or more simply:
T = r x F (whadaya know another calculated theoretical number)
Which is linier force multiplied by a radius. Of course this formula always assumes a perpendicular force axis to the fulcrum, something that just doesn’t happen in a reciprocating engine for more than a millisecond at a time.
From the Ole mechanic “You know when your on the entrance ramp to an interstate doing about 20 mph???? then you accelerate to say 70 mph and blend in???? Torque gets you to 70 mph, horse power keeps you there once you hit your speed and level off...............”
To put this into perspective the next time you want to accelerate really fast try shifting at your engine’s torque peak rather than the HP peak. It doesn’t take a rocket scientist figure out using which shift point will accelerate the car faster. This is because we’re talking about energy expended over time not a static applied force. To say that another way; I could put 84 pounds (that’s a Buell motorcycle’s peak output) of torque on the bike’s crank shaft with a ratchet handle, but I don’t think it’s going to accelerate too quickly and I doubt that the rider’d feel it to much in the seat of his pants either.
I find the whole argument over HP vs. Torque to be silly in the extreme because they are really one and the same, just expressed differently to show how the power is produced in any given engine for any given application. For instance a tow vehicle was mentioned; do we want high RPM power for our tow rig? I think not, we want it down low so that it’s managable and produces minimum wear on moving parts. How about the drag car? We want as much power as possible and since an internal combustion engine is in effect an air pump then we want as much air as possible to pass through the engine. All things being equal, the faster the engine is turned, the more air goes through it, the more power is made over any given period of time.
In summary, to disassociate HP and bow to torque is like saying that you really like chocolate cake but that chocolate is over rated. It just doesn’t make sense.
Steve
Threaded Mode
