There are three types of driving in the car: the front drive, the rear drive and the four drive. Then, among them, a considerable part of the “more understandable car” friends think that the four-wheel drive technology is the best. I personally think that the four-wheel drive system has its own advantages, but it is not perfect.
I want to argue from a few arguments.
Urban SUVs must require a four-wheel drive system
I am not saying that this statement is wrong. Since it is an SUV, a four-wheel drive system is definitely better than nothing. However, many people who have bought a city SUV may not have visited the field in the life cycle of his car. So in this case, is it more fuel-efficient than the two-drive version, and is it more useful to accelerate the slower four-wheel drive version?
I also don’t recommend that you drive a city SUV to off-road, because the four-wheel drive system of most city SUVs uses electronic limited slip, and can’t be mechanically rigidly pre-locked like traditional hard-core off-road vehicles, so at high intensity. In the off-road situation, the four-wheel drive system of the city SUV is very “chicken rib”.
On the contrary, I think that the four-wheel drive system of the city SUV is still used to cope with the rain and snow weather, and it is relatively stable in rain and snow.
When it comes to driving in the snow, there is a second very popular saying.
Snow must be driving a four-wheel drive
I think this statement is very far-fetched, because in the snowy weather, the performance of a car is determined: chassis clearance > tires > four-wheel drive.
Why is the chassis grounded first? This is actually very easy to understand: even if your four-wheel drive system is good, the chassis is too low to be dragged by the snow.
Let’s talk about the tires. Driving in the snow, no snow tires are difficult to move, because no matter what kind of driving form, the power is finally released on your wheel, then your tires can’t catch the ground at this time.
Only when the site ground clearance and tires meet the conditions, a good four-wheel drive system can play a more powerful feeling.
The four-wheel drive is stable
This question is actually very subjective and very difficult to talk about. Let’s put aside the psychological effects of most people. Let’s just say that after the four-wheel drive system is equipped, how much does the ultimate handling of this car increase? Or how much controllability has increased in the limit state?
First of all, there is no improvement in the limit maneuverability. The answer is definitely there, but it depends on which aspect: for example, the stability of the car when it is out, but when you are in the brakes, the four-wheel drive system is It doesn’t work at all, that is, if your cornering speed or your lateral G value exceeds the grip limit of the tire itself, the four-wheel drive system is powerless.
The four-wheel drive system can only assist you when you are out of the corner, can not improve the brake limit, and can not improve the corner limit.
The other one, the vehicle controllability under the limit state, everyone knows:
Most of the front-wheel drive breaks through the state where the tire grip is out of control. The front wheel loses the grip first, and the pusher, that is, the understeer, the vehicle will rush straight out. At this time, the method of saving the vehicle is to throttle the brakes and let the vehicle The weight moves forward, presses on the front wheel, restores the grip, and then completes the cornering. In the process of saving the car, the driver does not need to change the angle of the steering wheel, only use deceleration, which is a positive orientation correction. It’s relatively simple, so pushing the head is also the safest way to get out of control.
Most of the rear-wheel drive breaks through the tire. The state of the tire is out of control. The state is the tail. The rear wheel first breaks through the grip limit, that is, the over-steering, the vehicle will spin, and the rear-drive car is relatively difficult to rescue the car. The driver needs to correct the direction. At the same time, it is necessary to add some throttle, this is the anti-orientation correction.
And when the four-wheel drive breaks through the tire grip, the performance is: not necessarily! Nowadays, most of the four-wheel drive power distribution is not forever 50:50, but the vehicle’s electronic system automatically distributes the front and rear wheel power according to the state of the vehicle, so in this case, the over-bend is out of control. Or on the verge of out of control, you don’t know if the four-wheel drive system of the vehicle will allocate too much power to the front or rear wheels. You don’t know if you need to make a positive or negative correction, which will lead to a successful rescue. low.
4WD accelerates fast
This sentence may seem reasonable in people who don’t understand the car, because after all, how many legs are more than others, how can it be unhappy? However, as long as you are a little familiar with a little car sports, you will find out why the F1 car, and the American linear acceleration car are in the form of a rear drive?
Here again, there is a problem of “axis transfer rate”. The simple explanation is that in the process of vehicle acceleration, the weight of the vehicle will shift to the rear, so the power release and grip of the rear wheel at this time is Most importantly, there is no such thing as the front wheel with no power, because the grip on the front wheel and the ground is very low.
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