Every week, Exhaust Notes will pick out an industry, technical or obscure term from the automotive world and give you the lowdown on what it means and how it’s used. Already know the answer? Congratulations, you’re ahead of the game.

If you’d like an explanation of an automotive term, e-mail us at autosblog@live.com

This week’s term(s): Torque

Whenever you read about performance or heavy-duty vehicles, you hear about two things: torque and horsepower. Torque, essentially, is a measurement of force. Specifically, how hard the moving parts of the engine are twisting. A common metaphor for torque is turning a wrench -- if you have a 2-foot-long wrench and exert 100 pounds of pressure trying to twist it around a drainpipe, you are exerting 200 foot pounds of torque, because 100 pounds of pressure multiplied by 2 feet of wrench equals 200 (in the U.S., torque is measured in foot pounds or lb-ft; when using the International System of Units, like the Brits do, the measurements are different -- they use Newton meters, also written as Nm).

 

In your car's case, torque is created when internal combustion drives a piston downwards inside the engine. The movement drives a connecting rod that is attached to and turns the vehicle's crankshaft. Torque initiates here; after the crankshaft, the torque produced from its motion is applied all the way through the mechanism -- flywheel, transmission, etc. -- to the axle and, finally, turns the wheels.

 

At the lowest gears, the engine is designed to move maximum torque to the wheels (entropy dictates it's hardest to move a stopped car), but as the speed gets higher, less torque is needed. But, again, torque is measure of force. It tells you how much force the engine can exert on the wheels, which is good to know for towing capacity and high-performance cars (to get you off the line faster), but it doesn't tell you how fast said force is being applied -- that's horsepower, and that's a topic for another post.

Incidentally, one reason why electric vehicles can feel exhilarating is because they have their full range of torque available over a wide rpm range (this boosts acceleration across speeds); internal combustion engines have a very narrow rpm range when peak torque is used.