As the heart of the car and the source of power, the engine can be said to be the most valuable part of a car. And from a large part, it can be seen that the quality of the engine determines the quality and service life of a car. For example, the Toyota in the Japanese car, hundreds of thousands of kilometers do not need to be overhauled, the main thing is that the engine quality is excellent, basically there will be no problems. Of course, quality is one thing, and performance is also the key to measuring the quality of an engine. Some people think that the performance can be roughly judged by the speed of the engine at 120. For example, some cars have a speed of 120, the engine speed is very low and less than 2000 rpm, and some are as high as 3000 rpm. So, by comparing the speed of the method, can we judge the performance of the two engines?
First of all, we know that different engine tuning is not the same, from the torque curve of the engine, it can be seen that the maximum torque is a range range, in this range, the engine can reach the peak torque. However, the starting engine speed to reach the peak torque varies widely, some 2000 rpm begins, the peak torque range is 2000-4000 rpm, some cars reach the peak torque of 3000 rpm, and the speed range of 3000-5000 rpm is the peak torque range. The peak torque, which can be simply understood as the size of the car's strength, when 2000 rpm can reach the peak torque, indicating that when driving at high speed, the speed does not need to be too high The car is very powerful.
The 3000 rpm only reaches the peak torque, indicating that when driving at high speed, it is necessary to pull the speed up, otherwise the car has no strength, and if the speed is low, it will not be able to run. So can it be understood that when the speed of the vehicle reaches the peak torque at a certain time, the engine with a lower speed will perform better? In fact, this is not the case, although the range of the maximum torque of the engine is certain, but it must also rely on a parameter to reduce or increase the speed of the engine, so that the car can not only run but also save fuel when driving, which is the transmission ratio of the gearbox. The so-called transmission ratio refers to the ratio of the speed of the transmission input and output.
For ease of understanding, we can simply think of the engine and the gearbox as two gears, and the engine turns 4 turns the gearbox to 1 turn, and the transmission ratio is 4:1. Conversely, the engine turns 1 turn and the gearbox turns 4 turns, and the gear ratio becomes 1:4. When the car is hung in the first gear, the transmission ratio is the largest, and when it is hung in the highest grade, the transmission ratio is naturally the smallest. Therefore, if you want to make the engine speed lower at speed 120, you can only make the transmission ratio smaller, which is equivalent to the engine turning once, and the gearbox turning a lot of turns.
But the gear ratio cannot be reduced without limitation, its size depends on the torque of the engine, and the greater the torque, the smaller it can be. The torque of the engine is related to many aspects such as displacement and tuning, when the transmission ratio is very small, the engine has to use a lot of force to rotate. Just like the variable speed bicycle we ride, the front disc gear becomes the maximum, the rear disc becomes the smallest, then it takes more strength to pedal, but as long as you pedal slowly, the bicycle will run fast. Conversely, if the front disc becomes smaller and the rear disc becomes larger, it only takes a small amount of effort to pedal the bicycle, but the frequency of pedaling must be increased so that it can run fast. Therefore, if the torque of a car is relatively small, the minimum transmission ratio cannot be too small, otherwise the engine is difficult to drive the car.
For the vast majority of family cars, when the speed is at 120, the engine speed is often between 2200-3200 rpm, as long as it is within this range is reasonable. And it is not possible to judge the quality of an engine from this, because the factors that affect the performance of the engine also include displacement, gear ratio and tuning. The comparison between different cars cannot be judged according to the speed, but the same car can be simply compared. For example, the speed of the new car 120 engine speed is 2500 rpm, and after a few years of use, the speed becomes 3000 rpm, which means that the car may have problems and should be overhauled in time. Well, some knowledge about engine speed in this issue will be shared here, see you in the next issue.