In the characteristics of a vehicle, it is always a question of its power and its torque. These are 2 important elements to judge its abilities. But what exactly are we talking about? Are these major criteria for choosing an electric vehicle?
At comparable power, electric cars are more efficient than their thermal counterparts. A simple reason can explain this phenomenon: the maximum torque is present from the first turn on clean vehicles, which is not the case on conventional engines. It is this immediate availability of the electric motor torque when the current is injected that characterizes the efficiency of an electric motor. This is why the concept of engine torque is so important in an electric vehicle.
What is motor torque, the particularity of electric vehicles?
However, when it comes to defining the concept of engine torque, it is immediately more complicated. Even some savvy enthusiasts can get mixed up on this subject. Above all, you should know that torque is a force that acts on a body with a lever arm. From a totally theoretical point of view, the calculation of the engine torque is done using the formula of the ” law of the lever arm “. To calculate it, multiply the force (N) by the lever arm (m). The unit of measurement is called the newton meter (Nm).
Motor torque is therefore a measure of the acceleration of a car and indicates how much force is used by the motor in its rotational motion. Concretely, on electric cars, the curve of the engine torque is a downward curve: all the power arrives from the first seconds of acceleration, whereas it is necessary to wait for the ” optimal diet » (which corresponds to the rotational speed of the engine expressed in revolutions per minute) on a thermal car. That’s why electric vehicle drivers are guaranteed to be in front of you when the light turns green.
To give you an idea, on the Tesla Model S Plaid (the production electric model that accelerates the fastest) the motor torque is estimated at 1,400 Nm. On a Renault Zoé, it is 225 Nm, while on a thermal model like the Volkswagen Polo 1.0 TSI 95 from 2023, the engine torque drops to 175 Nm. In summary, the engine torque gives a fairly accurate idea of the acceleration available to a vehicle. Who says high torque, says driving pleasure and a certain safety to the driver when overtaking. On the other hand, without surprise, the more you press, the more you consume.
What does engine power really mean?
Michael Griese, director of electrical projects at BMW, sums up the difference between engine torque and engine power rather well. According to him, ” high engine torque enables efficient and energy-efficient driving while high engine power enables a car to accelerate quickly and reach a high top speed “. Power is calculated in horsepower, with reference to horsepower (hp), not to be confused with fiscal horsepower (fiscal horsepower, CV or administrative horsepower).
To fully understand, you have to go back to the 1770s and get lost in the Highlands of Scotland. 250 years ago, horses were the most common means of moving heavy loads. The term horsepower is attributed to James Watt, the Scotsman who contributed to the development of the steam engine. The unit of horsepower was devised to compare the power of an engine to that which can be obtained from a horse.
A horsepower corresponds to the power of a horse lifting a load of 75 kg over 1 m in one second. 1 hp equals 735.5 W. So the difference between torque and power is here. The unit of measurement in horsepower (hp) is used to calculate “ the speed at which work is done “, while the couple makes it possible to measure “ the force exerted to do this work “. Like torque, power is an important concept when choosing a vehicle.
Power is related to motor efficiency, a characteristic that indicates the amount of energy consumed that is actually converted into useful mechanical work. Last point, the power of an engine does not only measure its maximum speed. It depends on the speed at which the engine is running and obviously it is greater if it is running fast. In the case of electric motors, it is usually measured in kilowatts (kW).
What criteria should be taken into account on a clean vehicle?
For buyers of electric vehicles, engine power is not the main criterion. Torque is important, but in most cases it is also not one of the key arguments when choosing an electric car. Other factors such as range, recharging time or the environmental footprint of the vehicle play a crucial role when making the decision.
Above all, buyers are looking for vehicles that can travel long distances on a single charge. The other criterion scrutinized by future buyers of clean cars is the charging time. The capacity of the batteries is therefore of paramount importance. It is generally between 40 and 100 kWh. Be careful, when you choose an electric car, you should not only look at the capacity of the battery, but also its consumption and its real autonomy at high speed.
To calculate the range of an electric vehicle, simply divide the battery capacity by the average consumption of the vehicle and multiply by 100. Let’s take an example with the Hyundai Ioniq 6 and its 77.4 kWh battery. Its average consumption is announced at 14.3 kWh per 100 km. Its theoretical autonomy would therefore be 77.4 (battery capacity) / 14.3 (average consumption in RWD 18′ rims) x 100 = 541 km.
Among the important criteria for choosing an electric vehicle, comes the power tolerated in alternating current (AC) or fast charging (DC). In short, torque and engine power are no longer at the forefront of the criteria for choosing an electric vehicle.
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