Why are electric cars able to deliver power instantly, but gas engines take more time to build up power?
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Electric vehicles are powered by banked potential energy (chemicals stored in the battery). The motors have almost instant access to this power at all times as the conversion to power is very efficient.
Combustion engines have no bank of power to draw from so readily or instantaneously and make their power far less efficiently.
Edit: Stripped the answer a little bit too far back to bare bones, thanks for the corrections in the thread. Not strictly true on the stored energy comment about the battery. They store potential energy in the form of chemicals and a reaction does still have to take place but it is far more efficient and far far quicker than a combustion engine which is having to overcome many more physics hurdles like the inertia of the engine itself, being unable to just go from 0rpm to 5000rpm almost instantaneously to generate its reaction resulting in fuel becoming power etc.
Gas engines struggle to overcome their own mass at lower rpms causing lower torque availability, At higher rpms the ability of the mechanics to harness and convert the motors combustion peaks. There is also a limit to the fuel and air you can provide a cylinder. This all results in gas motors having a narrow band of rpm which provides ideal torque. CVT transmissions use schemes to vary their output rpm while maintaining the motors rpm with the ideal operating range to overcome the limitations that our previous generations 3, 4, 5 gear ratio transmissions allowed.
With Electric motors, if your batteries supply stable current, or you stabilize the current electronically, Then the force available remains unchanged across the rpm range. Speed may be controlled by varying voltage in simple DC motors, or by varying the rate of switching between motor coils in more advanced motors.
Electric motors drive like Iron Man flies. He just turns on the engines and he goes.
Combustion engines drive like Thor flies. He has to spin up something heavy to a certain speed before he can use it to carry him forward.
Electric motors usually have a flat torque curve. So at 0 RPM the motor can produce maximum torque.
An engine on the other hand has to get up to speed before producing maximum power. Maximum torque and horsepower are usually at 2 separate RPM.
Basically, combustion engines are air pumps.
You need some time to get the air in, mix it with petrol or whatever chemical is used for the combustion, etc…
That’s what is happening during the four strokes in which only one stroke is producing power.
It’s kind of like trying to push a little boat by blowing air on it vs simply pushing it with your finger.
They operate on fundamentally different principles:
As mentioned here the internal combustion engine requires combustion, so we are taking chemical energy, converting to thermal energy, and then the thermal energy is used to PUSH the pistons ( mechanical energy). This process alone takes more time and requires moving parts. The combustion process is rather complicated and the motion of the engine is required to make the process work. The fuel needs ( a mass than needs to me moved) to be sprayed or mixed with the correct amount of air (also a mass then needs to be moved) all inside of the cylinder, the cylinder then need to have a compression stroke to bring this mixture to a critical operating point, before it combusts, the combustion then rapidly expands the “air” (remaining air and the resulting gasses form the combustion) – and physically pushes the piston. In 4 stroke ( typical engines) the piston makes two in-out cycles for each combustion cycle. For a 6 cylinder engine at 500 RPM ( slow by engine standards), we get about 166 “explosions” per MINUTE per cylinder, or 3 per second per cylinder, that is not a very fast way to convert energy.
Conversely – an electric motor, also takes chemical energy, but converts it to electrical energy(in the battery) – and this process is always occurring or ON. This process is very quick and does not involve the moving of a mass. The electrical energy is then converted to mechanical energy in an electric motor. It is basic nature of an electrical motor that it produces torque based on two magnetic fields, so you can have essentially maximum torque (force) as fast as you can create a magnetic field.
A huge benefit here is you can have torque with no moving parts, granted, torque alone is not energy, but essentially max torque ( force) at Zero speed is the key.
How combustion engines get their power:
A cloud of gasoline is set fire to in a confined space with a piston on top. It causes the gas to expand, push the piston away.
That’s the basic operation of getting mechanical power out of an engine. If you do it more often, you get more power.
So, when a gas engine is turning at 6000 rpm, it has more or less access to twice the power as at 3000 rpm. Of course, as speed increases, you need to push harder against the wind and the inherent inefficiency of the car itself. But the power increase is initially higher than the resistance increase, leading to the feeling that you’re getting more power the faster you go. To a point.
How electric car get their power:
The stator moves an electrical charge around the rotor, causing it to spin. How big that electrical charge is depends on the power rating of the engine (the size of the wiring). It cares not how fast the engine is spinning.
So, as you accelerate, and you need to fight more against the wind and the ball bearings and tyres, it will feel as if you have less power available. Electric cars get max-torque at startup, when there is basically no force fighting back.
Gas engines use a complex design to draw air and fuel into the cylinder block, and then ignite that to push the piston. This generates the power. But the efficiency depends on a lot of variables. The width and length of the cylinder, the weight, the timing of the valves (these control the timing of air and fuel that get into or out of the cylinder).
An engine like this has a lot of flaws. Typically, designers will choose a specific power band for which they will optimize the design of the engine. This depends on the type of vehicle, the weight, the expected work load. A truck engine will need different power output characteristics compared to a family SUV or a sports car.
So, for example, a Porsche roadster might have peak power at 7K RPM. But when stationary, the car will idle at 1K RPM. The engine is not optimized to run at that rpm, so it gradually increases the power it can make as it revs higher.
On the other hand, an electric motor has a battery, and a motor that spins depending on how much electricity is fed into it. There’s no other variable in the energy transformation process, so the torque is the same no matter what rpm the motor is spinning at.
Gas engines extract energy from liquid fuel, and the rate they can burn the fuel is strongly related to the speed that the engine is running. Specifically a slowly spinning engine is limited in how much fuel it can burn.
Electric motors extract energy by using flowing current to create magnetic fields. The flow of the electricity can be mostly decoupled from the speed the motor is working at – i.e. you can flow a lot of electricity through a motor that is stopped or moving slowly.
Think about it kind of like a factory.
In an electric car, the battery says to the motor “Okay, we need to generate this much power” and the motor says “Okay, can do” and converts the electricity from the battery into mechanical power.
On the other hand an ICE is like a long assembly line.
The pedal gets depressed and the motor says “Okay, we need to generate this much power” and the fuel tank says “Okay, I’ll send the fuel” then the air pump says “I’ll mix in the air” then the sparkplug says “And I’ll ignite the mixture” once all that happens, a small explosion moves the piston up to turn the shaft, then the gas is exhausted out and the piston falls to turn the shaft the rest of the way. Then to keep generating more power, they have to do it over and over again.
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