Engine torque is a feature at least as important in a car as power. The torque expresses the rotational force of the engine, being created by the rotation of the motor around an axis. It is the force that gets a sports car from 0 to 100 km / h in a few seconds and “pushes you into the seat”. Engine torque is measured in Newton-meter (Nm).
Contents
How does car engine torque work?
In terms of theory, the torque is the force driven by a lever on a turning point. Engines with internal combustion transform the piston lifting and lowering movement with the help of the connecting rod, within a rotation movement of the crankshaft. The combustion of the air-fuel mixture in the cylinder creates pressure on the piston. This pressure pushes the piston with a force that pushes it down. Further, the gearbox transforms the engine torque into a propulsion force.
In the simplest terms, the torque is the force that turns the objects. For example, you can generate torque when you use a wrench to tighten the bolts of the car wheel. Basically, to use the key, apply a force on the handle, the force that creates a torque on the nut and twists it.
If we press with a force of 100 Nm (equivalent to about 10 kg) and the arm (wrench length) is 0.25 m (25 cm) then we will get a tightening torque applied to the 25 Nm bolt! To increase the torque we can increase the force of the push or the arm of the force.
In the case of a combustion engine, the engine torque is given by the product between the force pushing on the piston and the length of the lever arm (the force arm).
The torque can be improved by increasing the force of the pressing or by increasing the length of the force arm. If we compare a petrol engine with a diesel engine from the torque point of view, for the same cylindrical capacity, we will notice that the diesel engine generates a more substantial engine torque. The explanation comes from the fact that, for a diesel engine, the average pressure in the cylinder has higher values, so the pressing force is higher.
In general, a car will seem more responsive when the best torque is reached early in the acceleration process, but this is not always the case. The torque becomes more and more important as the vehicles get heavier. A small city car can be driven lightly with lower torque, while a larger SUV needs larger torque to move. It is the main reason that large cars are equipped with diesel engines. Diesel engines offer more torque at lower acceleration than petrol engines.
The efficiency of engine torque.
The engine torque reaches the peak value at a speed at which it is most efficient. In other words, the engine efficiency is at the maximum at a speed at which it produces a peak torque level. If you accelerate the engine above this speed, the torque starts to fall due to the increased friction between the moving components of the engine. So even if you’re revving the engine over the maximum torque, the torque will not increase.
Engine torque is multiplied by gears. If the selected speed is low (first gear), the greater the traction power of the engine is. However, if you run the engine while maintaining gear 1, after a while, it will reach a limit, which warns the driver to move to the next gear. In the opposite case, if you change the gear before the engine reaches maximum torque, the vehicle will lose acceleration. The reason? The wheels no longer have sufficient rotational force. Thus, the driver will be forced to pass in inferior gear.
To obtain the highest efficiency in fuel consumption, you must change the gears as close as possible to the torque peak value. At the same time, we recommend you select the correct gear that corresponds to the speed and number of rotations recommended by the specific model you drive. Once the car has exceeded 60 km / h, you do not need a large number of rotations. This means that when driving on the highway, it is best to use the highest gear and keep the engine under 2500 RPM to achieve maximum efficiency. Similarly, when climbing a slope, you must use a lower gear and a greater number of rotations per minute for the vehicle to climb.
Diesel engines vs petrol engines torque
Depending on the characteristics of the engine, different characteristics of the torque are also developed. Most cars produce a useful torque within a rather narrow range of the speed range. In the case of petrol engines, it usually starts around 1000-1200 rotations per minute and reaches a peak between 2500 and 4000 rotations per minute. In the case of diesel engines, it starts from 1500-1700 rotations per minute and reaches the maximum point at 2000-3000 rotations per minute.
Torque vs Horsepower
The torque differs from power (which expresses the horsepower number) because it refers to the amount of power an engine can develop, while horsepower defines how fast that power can be delivered. Both torque and power affect the speed of a car, so it’s easy to understand why many confuse them. In reality, however, the differences between them have a significant impact on the functioning of a car.
The greater the power of an engine, the greater the maximum torque potential. This potential translates into real applications through shaft and transmission characteristics. This explains why a racing car and a tractor with the same number of horsepower behave so differently. In the case of a racing car, all torque is used for speed, while the tractor uses horsepower to pull weights.
What is the difference between horsepower and torque?
Horsepower is measured at higher RPM’s and torque is measured at low RPM pulling power of an engine.
Should I choose a car with more horsepower or with more torque?
That depends on your needs, but one thing is for sure, cars with more horsepower winds races, and torque win pulling contests. Cars with greater horsepower will always have greater top speed, better acceleration, and overall better driving enjoyment. Torque is simply increased with a different gear change until a point.
How to calculate the torque of a car engine?
It’s not a simple formula, so a calculator should do everything for us. It is also a procedure where you find out if the dealer who sells you a car is telling the truth or is trying to sell you a higher torque than in the technical data sheet of the car. We found and tested some torque (Nm) and power (HP / kW) calculators and got the same result.
You should also try and compare the result displayed with the car specification. That way you will know what torque the car you are driving has. In the “speed” field, you must enter the RPM of the engine at which your car develops all the horsepower in the datasheet. You can also calculate, from the torque to the horsepower, to find the horsepower, by entering the speed at which you have the maximum torque in the “speed” field.