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

Question

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

In: 4

Answer 1

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.