I’ve heard that fact, and I know ICE cars have a torque curve but I don’t understand why it is that an electric motor produces torque instantly.
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well, it’s not *technically* instant. But electricity moves very close to the speed of light, and so when you touch the pedal, the signals move super fast, and the force is applied at a speed that seems instant (because you can’t actually perceive a delay).
ICE delay can be perceived, because gas/diesel needs to enter the engine, then get compressed, and then the explosion needs to send the energy along that turns the wheels. This takes significantly longer (even though it’s still pretty fast).
Torque is a function of rotation around an axis.
An ICE accomplishes it’s torque by spinning up to speed and using the rotational mass of the parts to give it it’s torque… Basically it’s ability to keep things turning. These peak numbers are up in the 1000’s of rpm.
An electric motor starts out with zero rotational mass (because it is not turning) and acts internally upon itself to give it’s torque as it begins to turn
…so it’s “instant” torque from zero.
Quite often electric motors actually lose torque as the rpm increases, but this is becoming less of an issue as motor controller tech changes.
A gas engine has gears that sync to the engine at a specific ratio.
So for example – if there’s a 1:1 ratio:
* The engine turns one time – the wheels on the car turns one time
* The engine turns 50 times – the wheels turn 50 times
* The engine turns 0 times – the wheels turn 0 times
But if the engine turns zero times – that means it’s off.
ICE cars have torque converters or clutches that wastes the engine’s force. This means the engine can keep turning so it doesn’t go off, while the car remains stopped.
If you drive a stick shift/manual car and don’t press the clutch as you slow down, the car can turn off when you stop. So you have to start the car and press the clutch pedal to deliberately waste the engine’s energy.
The torque curve is basically a graph over how much torque (force) an engine produces at different speeds. An ICE will have low torque at lower speeds because it can not get enough air and fuel into the engine to sustain the high pressure but needs to wait for the next rotation to get more air and fuel in order to ignite again. So torque increases with speed until eventually the drag is too high and the momentum of the air is working against the movement of the piston.
Meanwhile an electric engine works on completely different principles with the permanent magnet getting dragged around by the moving magnetic field around them. The force generated is a simple function of the angle between the magnetic fields and the strength of the magnetic fields. And since the moving magnetic field is controlled by a computer and can go at the same speed as the engine the angles stay the same and the torque generated stay the same. Unlike an ICE the speed of the engine is of little factor to the torque for an electric engine.
The magnetic field in an electric motor works even when the motor isn’t turning. You apply the current, and the torque is produced. From stopped to full speed, you are free to choose how much current to feed in and thus how much mechanical energy to produce.
ICEs don’t work that way. Torque isn’t a continuous product of physics, it’s the result of a mechanical machine trapping a chemical explosion. That machine produces torque in only one of its 4 strokes, which we compensate for with multiple pistons and balancing weights. That mechanical motion is also essential to draw in air and chemicals and continue the process. Because of this, when the ICE is turning more RPMs, it can consume more fuel and produce more energy.
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First, non-instant torque is not a property of ICEs in general, but specifically piston engines. Jet turbines are ICEs too, but they produce instant torque, exactly like electric motors.
The reason is simple: piston engine have to move pistons to keep going, and that is tied to the rotation of the shaft. The faster the shaft rotates, the faster injection-ignition-exhaustion cycle happens – the more torque is produced. If RPM is near 0, the engine cannot even go from one ignition to the next, and stalls.
The same is not true for electric motor or the jet turbine. Electric motor works on magnetic attraction-repulsion, and it does not depend on rotation of the shaft. Jet turbine works on fuel exhaust pressing on the blades, and it is also independent from shaft rotation. Both these engines can produce torque even at 0 RPM (you can block the shaft, and it will still provide force).
They just …. do. There’s no reason why they wouldn’t.
In an ICE, the power gets made when the fuel goes bang. That happens once per two revolutions per cylinder. The more revolutions the more bangs. So you gotta have the engine going at a certain speed to make power. A 4-cylinder engine has to spin around 5 times to make 10 bangs worth of power.
An electric motor just… doesn’t have this problem. The power can be turned on and off whenever. No big deal.
Actually some types of electric motors do have to spin to make power, but they don’t use those kinds in electric cars.
An electric motor is a series of electromagnets arranged in a circle that turn on and off at the right time to pull something around that circle. The torque is provided by the pulling force of the magnet. As soon as you turn on a magnet, you get all the pulling power instantly, so there’s instant torque.
In an ICE, the torque is provided by an explosion that has to be timed just right to push down the piston. Explosions don’t turn on and off instantly like magnets, so it’s much more difficult to time everything correctly. If the engine is going to slow or too fast the explosion isn’t timed correctly so you don’t get as much torque.
ICE, you press the pedal, gas go from gas line and gets ignited in piston chambers, blows up, causes piston to rotate slowly at first to faster, that rotation is transferred to the wheels through transmission and wheels turn
EV, you press pedal, electricity INSTANTANEOUSLY goes into electric motors turning the wheels
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