Trawling the net you find a lot of car enthusiasts talking about horsepower and torque, what they are, and which one’s better. But, as a lot of you have surely realised, there’s a lot of fake science being spouted by people who think they know what they’re talking about. So on this page we’re going to answer this question once and for all. What is the difference between horsepower and torque, and which one is better?
To answer this, we first need to define them.
Very simply, torque is a twisting force. If you use a wrench to tighten a bolt, you’re applying a certain amount of torque, in the same way an engine turns a crankshaft.
It’s usually measured in lb-ft, so let’s say you’re exerting 20lbs of pressure on a wrench that is 1ft long, you’re exerting 20lb ft of torque. That’s why if you use a longer wrench, it’s easier to tighten a loosen a bolt – you have more torque.
How does this change a car, though?
The more torque you have, the more push you have. Torque is the feeling that pushes you back into your seat and enables a car to accelerate. Ever heard someone say they have enough torque to not have to shift down a gear to overtake? A less ‘torquey’ car will need to be at higher revs to overtake like an MX5, a car with more torque, like a Chevy with a big American V8, doesn’t.
So is more torque better?
Yes, the more torque you have, the faster your car will accelerate. But of course there is the possibility that the car then becomes too powerful and will overcome its traction. Think Citroen 2CV with a bellowing V8 – can you see that ever going in a straight line?
Torque can also affect front wheel-drive cars, too via torque steer. Under acceleration in a high powered FWD car, the sheer torque of the engine can pull on the steering wheel. This is due to uneven driveshafts and sometimes, uneven road surfaces (we’re looking at you, England).
If torque is the push, then horsepower is the rate of the push or the speed at which it takes to apply torque. Because of that, we can define horsepower as the torque multiplied by the engine speed.
Horsepower = Torque X Engine Speed
Let me put this another way:
You’ve turned a corner and want to accelerate onto a straight piece of road. If you have a lot of torque, the engine speed doesn’t have to be high to produce a large amount of horsepower. If you’ve only got a small cylinder, the engine has to be turning faster to reach the same amount of power. This theory is also reflected in the power curves that a dyno run can give you. I’ll whack one below, and note that torque and horsepower figures will always overlap at 5252rpm. I’ll get into why that happens now.
The term ‘horsepower’ was invented by James Watt who was using ponies to lift coal. The average pony could do 22,000 foot-pounds of work per minute. He increased it by 50% for a horse and coined the standard 1 horsepower measurement as 33,000 foot-pounds of work per minute.
So, the reason torque and horsepower are always equal at 5252rpm is down to this…
So which is better – HP or Torque?
From what we’ve learnt so far, we know that there can’t be one without the other, and that both horsepower and torque do very different things to push the car on its way. Horsepower takes the car to its top speed and is the measure of work the engine can do.
Torque is the pulling power, or basically how easily the car can lug its weight around.
So, wee’ll end this article by saying that it’s completely down to you, the driver. If you tow a caravan or go off-roading, then obviously a more torque-y car will o you well. If you want a car to take on the track, then you’ll want a mixture of horsepower and torque, and if you want to zip around the back roads on the rev-limiter, then horsepower might be the way for you.