Four-wheel drive system

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Four-wheel drive system [Copy link]

Many people may think that four-wheel drive cars will have stronger ground-holding performance. In fact, they confuse the concept of ground-holding performance. The biggest difference between four-wheel drive cars and two-wheel drive cars is that FF models will understeer and deviate from the curve due to wheel idling, while FR models will drift. Since the power distribution of each wheel is automatic, four-wheel drive will not have the above problem. This is a problem related to the tracking performance of the car, not the ground-holding performance.

　　On the contrary, the four-wheel drive version and the two-wheel version of the same car often have stronger acceleration performance and ground-holding performance than the four-wheel version. The best example is Audi's A4, because the four-wheel drive car is heavier and has greater friction than the two-wheel drive.

　　The passive four-wheel drive system uses a mechanical transfer device, such as a gear-type torque sensing differential - Audi's Quattro, or a hydraulic transfer case - Porsche's 911 Turbo. The system intervenes only after the wheels are idling. The active four-wheel drive system is intervened by a multi-disc clutch controlled by a computer, such as Volkswagen's 4 Motion. The computer will continuously collect data such as tire speed and throttle size, and distribute torque before the tires start to spin.