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
My slower ev has about 350hp. My son’s bmw has about 450hp. So by the numbers being that our cars weight close to the same, he should beat me in a race. However his car only hits 450hp when the tachometer is in a narrow range (called the power band). So the reality is my electric motor is getting full power right off the start and I will beat his car off the line and it is only once his engine gets into the power band that he will catch up and pass me.
With internal combustion engines, there’s always a lag between pressing the accelerator pedal and the car engine responding, some is basic physics, some is actually deliberate to make the car easier to drive and more efficient (better mpg). The engine needs to spin up to a certain speed before it has enough torque (turning force) to make a difference. There’s a clutch and gearbox which might also drag out response.
With an EV, there’s lots of torque from stationary, and there’s no delay, which makes them feel very responsive, more so than a fossil fuel car of higher power.
Put your foot down at 1500 RPM, then at 4000 (on same gear). Noticed any difference?
Electric is always like at 4000.
With an ICE, when you step on the gas, the throttle opens and allows more fuel into the cylinders, this increases the power of the explosions in trhe cylinder, resulting in the engine turning over more quickly. This increased rate of revolutions is then mechanically transferred to the wheels, via a gearbox.
Every step of this process takes a certain amount of time to happen and that adds up to a noticable delay between your foot pressing the pedal and the wheels increasing their speed.
In an electric vehicle, there’s no delay. The instant your foot starts moving down, the wheels spin faster.
What they mean is torque at low RPM. An engine produces it’s peak torque at high speed (usually), it won’t make much at low engine speeds. An electric motor doesn’t really suffer from this disadvantage, it can produce most of it’s torque at any speed, even low speeds.
Something I think other explanations are missing about EV motors:
The turning force on an EV motor, especially at low revs, is directly proportional to the current you run through it, which is directly proportional to the voltage you put across it.
More voltage applied to the engine = more turning force (torque).
The voltage applied is controlled by the accelerator pedal which (in perhaps overly simplified terms) is basically a glorified lightbulb dimmer switch. If you slam the pedal down it’s like flipping a dimmer switch from off to fully on – essentially instantaneously you’re running full voltage across the motor so have full torque.
As you get to higher revs you start to lose some, as the current in the coils is changing so fast you run into issues with getting the current moving each step so you get some fade at the upper end of the motors operational revs, but down at zero revs you don’t have any of that – you’re at max torque from the moment you finish slamming the accelerator pedal down.
Some people think that their ice car has nearly instantaneous torque from their moment their foot hits the accelerator, but there’s always some lag time in reality. When you drive an ev it becomes very apparent how slow the ice is in comparison.
You know how a gas car takes a little bit to get get up to speed?
Compare that to a golf cart, or a radio controlled toy car. As soon as you press the accelerator, it starts going as fast as it can without any ramp up. The only thing keeping it from reaching max speed instantly is inertia of the mass it’s trying to accelerate.
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