Horsepower vs Torque – What’s More Important?
This question seems to come up on a fairly regular basis among vehicle enthusiasts that want to extol the virtues of the engine in relation to someone else’s. “Horsepower makes you go fast!” “Torque is what you feel!”
So, which is more important? Let’s try and answer the question. First things first, what does each mean?
Torque is a twisting force that rotates or turns an object, like a wheel. When you use a lug wrench on a bolt, you’re applying torque to it. Unlike horsepower, even if the object doesn’t move, torque can still be exerted on it. Torque is measured in pounds-feet, meaning a force in pounds acting on the end of a lever measured in feet. For example, if that lug wrench is 2 feet long, and you put 100 pounds of force on it, you are putting 200 pounds-feet of torque onto the bolt. A twisting engine crank works on the same principal.
The formula is understand horsepower is simple: Multiply torque by the engine speed (measured in rpm), then divide that by 5,252 to get the horsepower at that rpm level. In other words, to get the horsepower of a vehicle generating 400 pounds-feet of torque at 2,500 rpm, you would calculate (400 X 2,500)/5252, which equals around 190 horsepower.
Simply put: torque measures how much work is being done and horsepower measures how quickly the work is being done (or how quick the torque is applied).
Have a look at the chart below. This is for a standard 4 cylinder car and it shows the relationship of torque to horsepower (note how it crosses right at 5252 RPM as its always exactly the same there).
So, have we answered the question yet?
No, not really. Let’s complicate matters further. Most engines apply the amount of torque they can generate in different parts of the RPM spectrum. i.e. they can produce 150 lb/ft at 2500 RPM and 225 lb/ft at 4500 RPM. Electric motors are well known for their ability to produce maximum torque right from 0 RPM.
Why is this important? For any wheeled vehicle to get moving from a dead stop they have to overcome the inertia of not moving to the momentum of moving. That must mean torque is more important and the larger it is at lower RPM the better, right? Well, that does have some truth to it, but there are ways to get around it.
Just about every modern vehicle has a transmission which allows the engine to spin the wheels at different speeds relative to the engine RPM. Notice how a car feels faster in lower gears? That’s because the torque that the engine is supplying is being multiplied to be more via the transmission and differential putting more torque at the wheels of the vehicle. Look up the gear ratios and final drive of your vehicle. That number is the multiplier as to how much torque is being applied to the wheels and tires of the vehicle. Make sense?
So, it’s a combination of things?
It appears that way. Looking at all of the variables, it’s not a clear cut answer. Need to pull a heavy trailer? You need as much of that torque available at as low a speed possible. Driving an F1 car? Put that torque to work as many times as possible to make the tires turn as many times as possible.
Well that was disappointing
I know. We sort of answered the question, but not in an absolute manner like the article suggested. We’re sorry that we couldn’t come up with a definitive solution to settle this debate once and for all.
Just kidding, the answer is TORQUE and lots of it! Once you have that, use it and let Latium take care of all of your tire replacement needs!