Whenever I hear people talk about acceleration in electric cars, they talk about the instant torque. I think I have an okay understanding of what torque is, but what does it mean for it to be “instant “?
In: Mathematics
I think they mean in comparison to internal combustion engines which use gearing, and do not provide instant torque due to the clutch slippage.
Fun fact diesel trains use electric to get going out the station because a diesel engine just isn’t enough when it’s stationary.
It means an electric motor can apply its full rated “twisting force” (torque) from zero rpm.
An internal combustion engine has to build up some revs before its full “twisting force” becomes available. So if you have to build up, say, 3500 rpm, to the point where an engine is delivering its full torque, that takes time. An electric motor can deliver that full torque as soon as it starts turning.
Any combustion machine has his nominal torque at a given rpm,
while electrical engines have their nominal torque from the beginning.
In cars for example this has the effect that electrical cars accelerate from 0 to vmax with a continuous torque
without any lags like the combusting engines have while building up rpm or switch gears or enable turbo loaders.
Combustion engines have a delay from when you press the gas to when it actually moves the vehicle forward. You basically have to wait for a chemical reaction to occur in order to have power.
EVs store that power in the battery and can be brought out in an instant. Actually so much that they released an option to limit it. E.g. ‘Chill mode’ on Teslas.
Electric motors in a resting position have their magnetic poles as close to each other as possible, so when you apply electricity to the magnets they can impart their absolute maximum force instantly giving electric motors 100% torque from resting. Combustion engines cannot do this, they rely on a series of small well timed explosions being combined together to create a torque greater than the sum of its parts, so peak torque doesn’t occur until the engine is cycling fast enough.
When you hear about a cars horse power or torque number in a commercials it’s talking about its peak. When you step on the gas, it doesn’t always produce that number advertised. For example, my trucks peak torque is 600 ft pounds but that’s only at around 1600-2000 rpm. Higher or lower than that on the tachometer and it’s making significantly less power than that. You can look up your cars year make and model torque curve on google and you’ll see a graph. A combustion vehicles graph is literally a curved line. If you look at an electric cars torque graph, it will just be a block, or a square because you get full torque everywhere in the rev range.
It’s probably simpler and more accurate to think of it as constant power. Combustion engines will have a power curve which will provide peak power at one specific rpm and lower power above and below that.
An ideal electric motor will privide the same power output no matter which rpm you are at. This makes them much faster for accelerating an pulling loads and also means you need far fewer if any gears in the transmission and can even do away with the transmission entirely for some cases.
Do you know turbo lag? Instant torque is not turbo (or any other) lag.
An internal combustion engine has a lot of inertia working against it *and* it needs to not slow down too much or it will stall. If you just spin the engine to its max power RPM and drop the clutch hard, you’ll just stall the engine. You need to baby the contraption a bit, get it moving then gradually accelerate. In an EV the transistors close, the electromagnets are energized and you have the full torque on the wheels within *milliseconds*. Electric motors do not need to be rotating already to exert force (which is why your ICE car’s starter is one).
Let me put it to you this way. When I put the pedal to the floor in my Jeep Cherokee, it doesn’t start speeding up for 2 full seconds. It’s a 6 cylinder so it has some power, but the computer fucks with everything to improve efficiency. So once you get it revved up… after a few seconds… then it has ok power.
Electric cars don’t have this issue.
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