Torque is the grunty force that makes your vehicle good for towing and just generally overcoming its own weight. Practical Motoring explains what torque is.
LET’S TRY AND KEEP THIS brief, because otherwise we’ll all nod off. Everyone loves talking about horsepower… it’s sexy, but ask those who know, and they’ll tell you that torque is a far more important measurement.
Torque is a turning or twisting effort exerted by an engine or mechanism. Yawn. Think of it like this then, grab a spanner and place it onto a nut and then apply some twisting force to tighten the nut; the amount of twist applied is torque.
Power which, in Australia we measure as a kilowatt, will make your car faster, so, the more kilowatts the faster your car will go. But, if you want your car to move then you’ll need torque. They are two peas in a pod and one means nothing without the other.
Generally speaking, a vehicle will feel more responsive/grunty when its peak torque is developed lower down in the rev range, something that turbo-diesel engines excel at. Torque tends to become more important the bigger and heavier the vehicle becomes or its intended application, like a 4×4 or a vehicle being used to tow a heavy trailer.
Is torque always torque?
Torque generally refers to Newton metres (Nm) or, in the UK and US pound feet (lb-ft). And it refers to the amount of twisting force and engine generates at the crankshaft at any given rpm (revolutions per minute).
How to determine torque?
The best way to do this is via a practical explanation but in a nutshell, you’re multiplying the force by the length of the lever being turned. So, imagine you have a 100cm (1.0m) long spanner connected to a nut and you’re applying 100Nm of force/twist (one kilogram equals 9.8 Newtons) to the lever. So, the sum is: 100 (N) x 1.0 (m) = 100Nm.
To determine pound feet (lbft) of torque simply replace force with pounds and the length of the lever into feet.
Power or Torque?
One is largely useless without the other. Power will allow your vehicle to accelerate and drive faster because peak power is generally delivered higher in the rev range. But in a high torque motor, peak torque is generally delivered lower in the rev range and that’s because torquey motors aren’t designed to rev that high and so they’re ultimately not as fast as a vehicle that carries less torque but more power delivered higher in the rev range.
When it comes to towing, torque is definitely king. See, as we’ve identified, it’s torque that provides that low-down motivation for your vehicle while it’s the power (kW or hp) that makes it fast. But speed isn’t important when towing, rather it’s the ability to get at the meat of the grunt.
Hopefully this nutshell explanation has helped clear up just what that Nm describes in a car review.
Re your calculation to help explain torque, you may want to review the answer. The spanner is .5m long, not 1m long, meaning the correct answer is 50Nm not 100.
Thanks Dazza, I’ve fixed that now. – Isaac