Generally speaking, the higher the gear, the faster the speed, why does overtaking need to be downshifted? A lot of the answer is not clear, its practical formula is very easy to understand, downshift = speed increase = power increase speed .
Let's use a simple example, you and your crush goddess ride a speed-adjustable bicycle uphill, your goddess is in front of you, at this time your goddess says to you, "Come on, come on, come after me", at this time you are eager to rush forward, but found that you have adjusted the back gear of the bicycle to the smallest gear, the flat road is easy, but the uphill ride can not move. At this time, you adjust the rear wheel gear to the largest uphill and least labor-saving gear, increase the frequency of pedaling, and your car easily catches up with the goddess's car, and you sweetly hug together.
This example of riding a bicycle is actually the same as the process of our overtaking and downshifting. A big misunderstanding: the speed limit of the manual transmission is difficult for many people to understand one of the reasons why the overtaking car has to be downshifted is that the driving school coach tells them that the speed is more than 10km/h to 2 gears, and more than 20km/h to 3 gears, so in the minds of many people, the speed limit of each gear of the car is so much, for example, the speed limit of 2 gears is 20km/h. Of course, there are coaches who talk about changing gears at revs, but they don't explain why they do it.
Driving school let you do this for the sake of smoothness and fuel saving, does not mean that 2 gears can only be driven to 20km/h. If you want to drive more violently, wait until the speed reaches the red line zone and then change gears, and 3 gears can also break 100. Different gears represent different gear speed ratios, that is to say, if you want to maintain the same speed, the higher the gear, the lower the engine speed. Thinking clearly about this problem, why it is better to downshift and overtake. Why overtake the general family car, in order to make the car more energetic at low speed in the city, the torque of the low speed is adjusted very high, but it is impossible to take into account the high torque, the result is that the acceleration has no staying power, the engine is only four or five thousand rpm, and the acceleration begins to be weak. Overtaking is not most directly related to speed, but to acceleration.
Acceleration is related to torque, if you want more torque, in addition to stepping on the throttle to increase the speed, you also need the middle gearbox to help adjust the gear ratio, to amplify the torque output of the engine. The car's 1 gear gear ratio is between 4-5, 3 when the gear ratio is about 2, 5-6 gear gear ratio is generally about 1, so the lower the gear, the greater the torque of the car.
So suppose you are now in 6 gears, 70 per hour, at this time you need to overtake, you need to get a higher acceleration in an instant, so do two things, change to low gear, such as 3 gears, step on the throttle deeply, while increasing the speed and changing the gear ratio, the torque of the car increases instantaneously, bringing a short acceleration to help you surpass the car in front.
Why the overtaking car should be downshifted, in fact, it should be very clear. We just need to remember that speed is not the most important amount when overtaking, acceleration is the most important, changing the gear to increase the speed, can improve the acceleration of the car. When it's time to overtake, downshift is right!