Why is torque important for off-roading, towing capacity, etc?


Why is torque important for off-roading, towing capacity, etc?

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Torque is basically force in a twisting motion. How much of this an engine can output is important for how hard something can be turned, like a drive shafts or wheels.

Some situations make turning the wheels of a vehicle more difficult. Like if you attach a heavy weight to the vehicle, or if the wheels are not on a flat road surface. In those situations you want more torque.

Short version: Torque is the ability to do work. Horsepower is how fast that work can be done. You need to do a lot more work to move more weight or through more obstacles.

The torque CURVE matters a lot, too, though. Manufacturer’s post the peak outputs of their engines, but those outputs follow a curve over different RPMs. If you can make a LOT of torque, but only at a high RPM it’s much harder to utilize that torque in a low-speed situation like offroading or taking off from a stop at towing. You have to have ridiculous gear ratios going to get the engine to move fast while the wheels are still going slow. So engines that can produce a lot of torque at relatively low RPM (<2500) can be more valued for towing and offroading than engines which have a higher peak output but lower low-range torque.

Electric vehicles are kinda cool about this. Theoretically speaking, an electric motor’s torque is limited only by how much power you can shove through it without melting the components. It’s part of why acceleration is so impressive in electric vehicles and why REALLY high torque scenarios like freight trains have been diesel-electric for a LONG time.

Horsepower is torque x rpm. Rpm are not high when starting from a stop, therefore horsepower is irrelevant when off roading or towing. So the higher the torque number, the better because hp is irrelevant at low speeds. The rest of these answers are off base.. lol

Torque is the direct measure of how much mass your car can accelerate, and how quickly it is accelerated.

The motor puts out a torque (which is the number the car manufacturer puts on the label), a twisting force if you will, at a certain speed. Now that speed is way to high, but the gearbox can change that to a lower speed with higher torque. That higher torque is transfered to the wheels. The wheels now take that torque and apply it on a certain distance to the rotational axis (radius of the wheel), which makes it a force.

Quick insert here: torque = force * distance from axis. So it is basically the same phenomenon, but force works in a straight line and torque works around an axis.

Force = mass * acceleration.

The more mass you want to accelerate, the more force you need. The more acceleration you want, the more force you need.

Power on the other hand is just the statement at which speed the torque takes place. The total amount of “oomph” it can produce.

Now you may think that torque is the thing you want in a sports car aswell, because it is the thing thet pushes the car forward. That’s correct, but we’re talking about wheel torque as the cause of acceleration. If you have high revving sports car it may have less torque than a truck but still feels quicker, because it can stay in the lower gear (high wheel torque) for a longer time until it needs to shift.

Torque is a force multiplied by a lever arm distance. So when you’re tightening a bolt with a torque wrench, you apply, say, 100N at a distance of 0.5m along the wrench, that’s 50Nm of torque.

By contrast, power is force multiplied by distance per second. So if you imagine an engine attached to a brake drum, power being generated is the frictional force the brake applies, multiplied by the speed at which the brake surface is moving (this is how engines used to be tested and is the origin of the term Brake Horse Power).

When an engine generates a certain torque, it’s transmitted through the drive train, and the drive wheels convert it to a force pushing the vehicle forward. When towing or off roading, the peak motive force you can generate to move the vehicle at low speed, by generating torque, is more important than peak power, which is more applicable to the top speed the vehicle can achieve.

Let’s say you want to go rock crawling. A lot of the time spent rock crawling you need to move very slowly.

So, you need especially short gearing — most cars with a manual transmission can’t really travel slower than around 5 MPH comfortably. That’s why manual drivers hate stop-and-go traffic jams.

Therefore, you get a car with short gears that allow you your engine’s idle speed to make the car move at like 1 MPH instead of 5 in your shortest gear. Ok, great.

Horsepower is torque multiplied by the engine’s RPM. Torque can be pictured (to simplify things) as how much “oomph” the engine makes *each time it rotates.* Continuing with the analogy, horsepower is the amount of “oomph” the engine can generate in a given period of time.

Let’s say you need a combined power output of 60 “oomph”s per second to climb a specific rock (yes, I just made it a unit of measure for some reason). You could theoretically get this amount of power with an engine that makes 1 “oomph” per rotation, but spins 60 times per second (3600 Revolutions Per Minute, or RPM). Alternatively, you could make the same amount of power (60 “oomph”s) from an engine that makes **6** “oomph”s per rotation that is spinning at 1/6 of the speed — 600 RPM, which is 10 rotations per second.

If you have to crawl *at* 1 MPH (or close to it) due to the terrain, your gearbox is dictating that your engine will be stuck near its idle speed. So there’s no chance a small engine that only makes 1 “oomph” per rotation could let you climb this rock, because you’re stuck at like 600-800 RPM (near the car’s idle speed). There isn’t enough revs to let the small engine produce the required power. However, the engine that makes 6 “oomph”s every rotation *would* work here. Even spinning slowly, it can make enough power to pull the car up the rock.

If your car makes a lot of torque even at very low RPM, then it can still generate enough “oomph” to keep itself moving at slow, controlled speeds while doing things like climbing rocks.

This is also an over-simplification in the sense that gas-powered cars don’t make the same amount of torque at every engine RPM. There is another comment in this thread about the “torque curve” which shows how much torque the engine makes at varying speeds. For the reasons described above, you’d probably want an engine that makes a good amount of torque at low RPM for off-roading.

It comes down to environment:

Premise 1: All engines have torque, we say an engine has a lot of torque when the torque is distributed at a wide range, this means a lot of force down low.

Premise 2: Power focused engine do the opposite, they have the torque, but only high up. It’s good as long as you can keep your engine high up.

So how does it work:

Off road and similars do include continuous and quick changes of environment, rocks, trees, mud. You need to be able to throttle up and down very fast and need to add or remove power in RESPONSE to things.

The opposite, on a road, you plan ahead and all you need is to have power. To have power, you just need an engine that spool high. You set the proper gear in advance, keep the engine revs high and boom, you always have the maximum power available.

Off-road, you may be on a high gear and hit a tree root and you suddenly have to do something, if you shift down, by the time you do it, you gonna be stopped or overwhelmed by the obstacle. But if your engine is designed to have torque, it means that the engine will do a lot of force at ANY speed. The obstacle may have pushed your engine to spool very slowly but it still has the kick to lift itself up if you slam the gas.
That’s the point of torque focused engines. The engine can kick you forward whatever is the gear, speed, and engine revs.

It’s also the main focus for tractors and truck engines.

It isn’t directly. What people mean when they say an engine has lots of torque is that it has a wide power band with plenty of power at low revs. This is useful for offroading since you need a lot of power at low speed.