Driving method

The drive mode refers to the layout of the engine and the number and position of the drive wheels. A typical vehicle has two rows of front and rear wheels, one of which is driven directly by the engine, so that the wheels that propel (or pull) the car forward are the drive wheels. The most basic classification criteria are two-wheel drive and four-wheel drive, depending on the number of drive wheels.

First briefly introduce the two-wheel drive: In the two-wheel drive form, according to the position of the engine in the vehicle and the position of the drive wheel, it can be further subdivided into a front-rear drive (FR), a front-precursor (FF), and a rear drive. (RR), middling rear drive (MR) and other forms. At present, the two-wheel drive vehicles and cars are most commonly used as front-rear drives.

The full name of the front-rear drive (FR) is called front-engine rear-wheel drive and is a more traditional form of drive. The front wheels are responsible for the steering, and the rear wheels are responsible for the entire vehicle drive. In this type of drive, the power of the engine output is all delivered to the rear axle, driving the rear wheels to move the car forward. In other words, the actual progress is that the rear wheels “push” the front wheels to drive the vehicles forward.

Pre-drive has a greater advantage. When the vehicle starts, accelerates or climbs on a good road surface, the adhesion pressure of the driving wheel increases, and the traction is obviously better than that of the precursor. At the same time, vehicles with front-rear driving also have good steering stability and ride comfort, and are conducive to extending the service life of the tire. In addition, the arrangement of the front and back drives enables the vehicle's engine, clutch and transmission and other components to be close to the cab, simplifying the layout of the operating mechanism and the structure of the steering mechanism, which is more convenient for vehicle maintenance and repair.

BMW 5 Series Front Rear Drive

The full name of the pre-precursor (FF) is called front-engine front-wheel drive, and this type of drive is commonly used in mid- and low-end cars. It is generally responsible for steering at the same time as the front wheel is also responsible for the vehicle's driving work. This type of driving will exhibit a little more understeer during exercise, but it is also more conducive to driving safety of the vehicle.

Audi A6's predecessor

The full name of the rear rear drive (RR) is called rear-engine rear-wheel drive. It was widely used in small cars in the early days. Now it is widely used in buses and it is rarely used on cars. However, the “drift” of the Porsche 911 is Known for the RR. The advantages of RR are: compact structure, no heavy transmission shaft, no complicated front steering and driving structure. The disadvantage is that the rear axle load is large, and in terms of maneuverability there is an oversteer tendency opposite to FF.

Porsche 911 rear rear drive

The full name of the mid-engined rear-wheel drive (MR) is called the mid-engine rear-wheel drive. The engine is placed between the front and rear axles, and the rear-wheel drive is used at the same time, similar to the layout of the F1 race car. The advantage of MR is that the shaft load is evenly distributed and has a neutral handling characteristic. The disadvantage is that the engine takes up space in the cockpit, which reduces the space utilization and practicality. Therefore, MR is mostly a sports car that seeks to control the performance.

Ferrari F360's mid-engined rear-wheel drive

Based on the above many advantages, domestic BMW 325i, 530i and higher-grade imported BMW sedan, Bentley, Mercedes-Benz, Jaguar and many other luxury cars use pre-driver.

A two-wheel-drive vehicle may slip even when it is on a good road, encounters snow or slippery roads, and tends to swing when starting up. Four-wheel drive can prevent this from happening. At the same time, the four-wheel drive system has superior engine driving force application efficiency than two-wheel drive, and can achieve better tire traction and effective steering force. As far as security is concerned, better driving stability can also be achieved.

The so-called four-wheel drive means that the front and rear wheels of the vehicle have power, and the engine output torque can be distributed to all front and rear wheels in different proportions depending on the state of the running road surface, in order to improve the driving ability of the vehicle. Usually expressed as 4X4 or 4WD. If you see a word on a car, it means that the vehicle has a four-wheel drive function. In the past, four-wheel drive was unique to off-road vehicles. In recent years, some high-end cars and luxury sports cars have gradually acquired this configuration.

Part-time 4WD------ This is a four-wheel drive system where the driver can manually select between two-wheel drive and four-wheel drive. Disconnect the splitter to change the two-wheel drive or four-wheel drive mode, which is the most common drive mode for general SUVs or four-wheel drive SUVs. The most significant advantage is that the drive mode can be selected according to the actual situation, which is more economical. Driving on the highway uses two-wheel drive gear; when encountering rain and snow road conditions, four-axis drive is selected to enhance the vehicle's adhesion and handling.
Full-time 4WD ------ This drive system does not require the driver to choose to operate, the front and rear wheels will always maintain the four-wheel drive mode, set the engine output torque at 50:50 before and after On the wheel, keep the same amount of torque on the front and rear wheels. The full-time drive system has good driving maneuverability and driving trackability. With a full-time four-wheel drive system, it can smoothly drive on paved roads. However, its shortcomings are also obvious. It is the comparison of waste oil and its economy is not good enough. Moreover, the vehicle does not have any device to control the difference in tire speed. Once a tire leaves the ground, it will often make you stagnate there and cannot move forward. However, this year has also developed some intelligent full-time four-wheel drive systems, such as Audi's quattro, when it comes to special roads, he can redistribute torque and distribute more torque on non-slip drive wheels to solve the problem. The drawbacks of the old-fashioned full-time four-wheel drive.

Audi allroad quattro

Real-time 4WD Vehicles with a timely drive system can use a computer to control the drive mode selected to suit the current situation. On normal roads, vehicles are generally rear-wheel drive. Once encountering a bad road condition or a slippage of the drive wheel, the computer will automatically detect and immediately assign the engine output torque to the two front wheels, naturally switching to a four-wheel drive state, eliminating the driver’s judgment and manual operation. The application is simpler. However, compared with the human brain, the computer has been slower to respond, and as a result, it has also lacked the sense of conquest and driving pleasure that it is all in its grasp.