Torque = Amount of Work — Horsepower = Speed of Work

Torque is measured in foot-pounds.  So 100 ft-lbs of torque could be moving 100 lbs over 1 ft or it could be moving 1 lbs over 100 ft.  Torque is a measure of work, known scientifically as Force x Distance.  Torque also doesn’t tell you how long it takes to get there. The work can be done over 1/10 second or 5 seconds.  (Just like the new guy burning up his clutch “tryna” get off the line.)  Torque only measures the amount of work it never measures the speed.  So you’re about to find out why some people say torque is low end speed and power is higher RPM speed.

Power is defined as: Power = Work / Time.  You read that correctly.  Power is the amount of work over the amount of time it takes this to happen.  Power is the speed at which the work is done.  Still need more help?  Power is how fast that little piece of crap you think is cool actually goes.  The 50% of you that think torque is low RPM speed have just tuned out.  You’re no longer listening because somebody who thought you were too stupid to understand equations explained it in a way that skipped all the math.

To make this easier I’ll give you an example.  Let’s say we have 100 ft-lbs of torque at 3000 RPMs.  The actual formula to convert that into horsepower is (Torque x RPMs) / 5252 = HP.  So 100 ft-lbs x 3000 / 5252 = 52HP.  Now let’s say you make the same 100 ft-lbs of torque, but at 5000 RPMs.  Now you have 95HP and you’re doing quite a bit better.  At 8000 RPMs with the same 100 ft-lbs of torque you would have 152HP and so on.Now you can see why some people refer to lower RPM speed as torque.  Since the RPMs are small, a huge increase in torque is required to make more power and you can clearly see the relationship between torque, power, and speed.  At higher RPMs the RPMs multiple the torque so much that the relationship doesn’t always feel quite as direct.  Just remember that any time you are describing the speed of moving a mass you are describing power.  You’re describing the speed of the work not the amount of the work.

How Torque and Horsepower Relate to Tuning

Torque must always be converted into power in order to have some meaning related to speed.  But since HP is only a function of torque and RPMs, you can’t actually tune an engine for horsepower.  The torque is directly related to the amount of air inside a cylinder.  Torque is what is being tuned.  But since you want speed you must set your goals in terms of horsepower.  So the design of an engine’s performance is centered around horsepower.  You must work backwards from that point to determine where to place the torque to give the horsepower in the correct ranges.

The Argument Continues

So the next time someone tells you that torque is low RPM speed you can either explain some physics and formulas or you can just smile and say, “Nah, man, it’s all about power.”  The argument goes on.


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