Originally Posted by **DGthe3** *Warning: Technical Post*
In basic terms, torque is a force at a distance (pounds are force, feet are distance, lbs x ft = torque). So, the more force you apply the faster you accelerate (Acceleration=Force/mass). Alternatively, when expresed linearly the units of torque are equivelent to lifting 1 lb of weight 1 foot off the ground.
Horsepower is torque/time. So, the faster you can exert the same torque the more power you have. In the case of cars, speed is revolutions per minute (rpm's). Hp=(torque*revolutions)/(minutes*5252), or more simply Hp=torque*rpm/5252. Transmissions are based on this equation. They trade revolutions for more torque. But the power remains the same (minus frictional losses).
Now, lets get back to torque vs hp. Before we begin, these numbers are purely for illustrative purposes, I basically made them up as I went. Lets say you were repairing your roof. You've got 3 buddies to help you bring supplies up to the roof 20 ft off the ground. Bob can bring up loads of 100 lbs in about 2 minutes. Joe is weaker, but quick. He can only manage 50 lbs at a time but he does it twice as fast a Bob. Your third buddy is Frank. Like Bob he can bring up 100 lbs at a time but like Joe he does it in only 1 minute.
. Bob . . . . . . . . Joe . . . . . . . . Frank
100lb*20ft/2min . 50lb*20ft/1min . 100lb*20ft/1min
0.1904 hp. . . . .0.1904 hp. . . . .0.3808 hp
So, Bob and Joe are equally powerful but they are half as powerful as Frank. Another way to look at it is given the same power you can be strong and slow or weak and fast. Never both. To get both, you need more power. You need a Frank.
this is all well and good for comparing 1 particular hp value against another and would lead one to believe that 300 hp is the same no matter what. That is both correct and wrong at the same time. More torque gives you more power at lower speeds. Which means that when cruising down the highway at 1500 rpm the 4.6L v8 in the mustang would give much better acceleration than the 3.6L V6 from the Camaro, if they were in the same car and the same transmission. Since the mustang is lighter than the Camaro it is no contest. The two will only have similar performance when they are both at their peak RPM.
Hp vs torque, I take hp. RPM vs hp, I take hp. Torque vs RPM, I take torque. |