Many people think that a four-wheel drive car is designed to overcome difficult off-road conditions. That is, all-wheel drive increases only the vehicle's cross-country ability. This is not entirely true. Yes, four-wheel drive increases cross-country ability, but it can also be used on cars. But no one has yet taken it into his head, for example, to storm a dirt road soaked with rain on an Audi A4 ... Why does a passenger car need four-wheel drive? It's simple, to improve security.
A four-wheel drive car is more stable on slippery roads, it is safer to drive smooth long turns on it. Therefore, many automakers also produce all-wheel drive cars. Not all potential car owners are ready to buy a car with all-wheel drive. Maintenance of such a car is more expensive than usual, and fuel consumption is somewhat higher.
Therefore, automakers have found a compromise between efficiency and safety. These are cars with automatic all-wheel drive. By default, the car is front-wheel drive or rear-wheel drive, but when the drive wheels slip, the electronics connects the second drive axle.
Many crossovers use just such a scheme. Ground clearance on crossovers is greater than on passenger cars. Therefore, very often they are equated with SUVs. Potential buyers do not delve into the design and buy cars with this layout. And of course they operate their iron horse like a real SUV. This naturally leads to a breakdown of the all-wheel drive connection system.
Principle of operation
The all-wheel drive connection system is quite reliable. But you must always remember and understand that a crossover cannot and should not move off-road. He is contraindicated in severe road conditions. And if the driver still got into an unpleasant situation, you need to correctly use the capabilities of all-wheel drive. On vehicles with such a system, there is a control button. The button is usually installed on the auto panel and allows the driver to select automatic mode or turn on all-wheel drive.
In automatic mode, the control unit itself “decides” when to connect the all-wheel drive. When manually engaged, the four-wheel drive works all the time, that is, the second drive axle clutch is locked (on). To protect units and mechanisms from large overloads, automatic shutdown of forced blocking is provided. Shutdown occurs when a certain speed is reached during acceleration. But the shutdown does not occur completely, the system goes into automatic mode.
Device
The all-wheel drive clutch is installed on the GP gearbox. On the one hand, a cardan is connected, going from the RC to the rear axle, and the output shaft of the coupling engages with the shank of the GPU.
When the car is moving, the cardan rotates, but the bridge itself does not work. The GP rotates from the feedback of the wheels with the road at idle, the torque from the gearbox is not transmitted to the wheels. When switched on, an electric current is supplied to the magnetic coil of the clutch. Under the action of a magnetic field, a package of special friction discs is compressed. Due to friction, the entire package becomes a single body and the rotation is transmitted to a special unit, which, in turn, mechanically compresses another package of friction discs. Now the rotation is transmitted to the shank of the GPU and further to the wheels. The clutch housing is filled with oil.
Attention! GP oil and clutch oil do not mix during operation. Transmission oil is poured into the GP, and special hydraulic oil with increased friction properties is poured into the clutch. Such oil simultaneously lubricates the entire mechanism and improves the adhesion of the friction discs to each other. It is forbidden to pour ordinary gear oil into the clutch.
Breakdowns
If used incorrectly, the clutch cannot cope with the increased load and fails. In automatic mode, a non-constant voltage is applied to the electromagnet winding. The control unit, depending on the conditions, supplies a pulsed current. The more torque is required to be transmitted, the longer current pulses are applied to the winding. Friction discs are then compressed, then released. At the moment of adjoining of disks to each other there is their intensive wear.
At the same time, the node that compresses the second clutch pack perceives variable loads and also wears out. The second clutch package acts as a damper, smoothing out sharp clutch engagement due to slipping of the friction discs. This is necessary for a longer service life of the GP gearbox itself.
When the clutch is turned on and off, due to the friction of the clutches, the entire mechanism heats up. Strong heating can lead to boiling of oil in the clutch cavity, resulting in increased pressure inside.
The seals are starting to "snot". Also, when the pressure increases, the control clutch pack (which is activated by an electromagnet) is compressed without electricity, and the clutch does not turn off. It's hardly noticeable in a straight line. But when the car turns, the friction disc packs cannot cope with the increased load, the discs begin to slip, making a grinding sound. There is intensive wear of both packages.
With very high heating, an interturn circuit is possible in the winding of the electromagnet. If the driver complies with all operating rules, it is enough to monitor the oil seals to avoid oil leakage. If oil leaks, the clutch will remain without lubrication and heat up. The result of overheating is described above.
How to avoid clutch breakage
It is possible to avoid or at least extend its service life. The less often the car is used off-road, the longer the clutch will last. When overcoming small difficult sections, full blocking should be included. You should not rely on the automatic mode, in such conditions it is not optimal. While driving, you do not need to sharply press the gas, sharply brake. Even when completely blocked, such actions adversely affect the life of the clutch. You should drive in low gear. There are situations when difficult conditions are encountered on city roads. The front axle of the car is on ice, and the rear axle is on dry pavement. Constantly pressing the button is not very convenient, but you need to move off in such conditions as smoothly as possible.
As often as possible, visually inspect the clutch housing for oil leaks. Little oil is poured, so if it leaks, it will flow out very quickly and this will lead to breakage. At the first symptoms of a malfunctioning clutch, you must immediately stop driving. A timely stop will help to avoid serious damage. If possible, deliver the car to the place of repair on a tow truck. Towing is not recommended.
Clutch repair
No matter how correctly and competently the driver does not operate his car, the all-wheel drive clutch can still fail. Dealerships change the clutch assembly, as it is very problematic to find spare parts. The most common failure is the jamming of the clutch in the on state. This happens more often due to overheating.
When repairing, you need to disassemble the mechanism, visually inspect all parts for wear. If the parts are in satisfactory condition, thoroughly rinse everything and blow with compressed air. Check the bearing for play and noise when turning by hand. If the bearing has play, noise during rotation, it should be replaced. An analogue can be selected by size.
With a high mileage of the car, it is advisable to change the oil seals. Their service life is pretty decent, but still not worth the risk. Seals can be selected by size and marking. It is imperative to change the sealing ring of the clutch cover, lubricate it during installation and make sure that the edges do not lift up. If the O-ring is damaged during installation, it is possible for the HP oil and the clutch to mix during operation, which is not acceptable.
The same applies to the inner oil seal, which is installed on the HP side. Fill with new oil before installing the cap. Insert the assembled clutch into the housing, while adjusting the gap between the movable plate and the housing. It is important that when the electromagnet is turned on, the plate does not touch the clutch housing.
Elastic cardan coupling
Another common failure is the hum while driving. The clutch bearing usually hums. When replacing it, carefully inspect all parts of the coupling for wear. It is advisable to change the oil at each disassembly in order to prevent wear products from entering the mechanism.
Rarely fails the winding of the electromagnet. It is possible to check its work directly on the car. Apply 12 V voltage to the connector pins, a click should be heard. And if you take the clutch with your hand, then at the moment of switching on you can feel a slightly noticeable knock inside the clutch. This indicates the health of the electromagnet.
All-wheel drive clutches for Hyundai Tucson and KIA Sportage are identical. They differ only in the outer case, depending on the year of manufacture of the car. They also differ in part numbers. In the event of a breakdown, it must be completely replaced. But if desired, the clutch can be repaired on its own and at a lower cost. The most pressing issue with self-repair will be the search for spare parts.
Good roads and good luck with the repair!
On many cars, all-wheel drive is pluggable. The all-wheel drive on Chery Tiggo cars is also arranged, the rear-wheel drive is connected here automatically, through an electromagnetic clutch.
The clutch is controlled by the four-wheel drive control unit. The principle of operation of an electromechanical clutch is almost the same as that of a clutch. When voltage is applied to the clutch, the discs inside the clutch are pressed against each other and torque is transmitted to the rear wheels through them.
Four-wheel drive is connected to Cherry Tiggo only at the moment of slipping of the front wheels, and approximately after the second rotation of the wheel. When the need for all-wheel drive disappears, it turns off. Also, the drive is switched off when a certain speed threshold is exceeded, because the clutch operation is not designed for high speeds.
There is a four-wheel drive test lamp on the Chery instrument panel. When the ignition is turned on, the lamp lights up and the system performs a self-test. If everything is in order, the lamp goes out. In the presence of malfunctions, the lamp will continue to burn.
Unfortunately, there are no identification signs that the drive has turned on in the car. But you will easily understand this when you get stuck and start to slip. When the rear wheel drive is connected, you will feel a slight push, and the car will slowly start to climb out of the blockage.
Torque to the rear wheels is transmitted through the transfer case (2), front cardan (4), electromagnetic clutch (5), rear cardan (6), rear axle gearbox (7) and rear wheel drives.
Vehicle all-wheel drive transmission diagram
1 - gearbox, 2 - transfer case, 3 - front wheel drives, 4 - front cardan gear, 5 - electromagnetic clutch, 6 - rear cardan gear, 7 - rear axle gearbox, 8 - rear wheel drives.
Transfer case
The transfer case is rigidly attached to the gearbox housing. The drive for the razdatka is the differential box. The transfer box itself is two-stage. There is no center differential in the transfer case, and the redistribution of torque between the axles is performed by an electromagnetic clutch, depending on road conditions.
Shafts of cardan gears are made of thin-walled steel. The electromagnetic clutch transmits torque to the rear wheels only when the clutch is partially or completely blocked by a signal from the four-wheel drive control unit.
The all-wheel drive control unit is located under the driver's seat. The drive unit receives information from the engine control unit and, based on the data received, turns on or off the clutch, thus applying or removing torque to the rear wheels.
The block receives the following information:
- longitudinal acceleration of the car (from the acceleration sensor under the dashboard console)
- vehicle speed and wheel speed difference (from wheel sensors)
Four-wheel drive is a design of an automobile transmission that transmits the torque generated by the engine to all wheels. At first, such a system was used only for all-terrain SUVs. But, since the 80s of the last century, it has become widely used by many manufacturers to improve the road performance of manufactured cars.
The main advantages of an all-wheel drive transmission are:
- Better grip on slippery roads.
- Increases the efficiency of the engine.
- Acceleration is faster.
- Significantly improved handling characteristics.
- Increased permeability.
The main disadvantage of such transmissions is the complexity of the design, which entails a high basic cost and the cost of repair. In addition, it leads to some increase in fuel consumption by the car.
According to the principle of operation, all-wheel drive systems are divided into:
- Permanent four-wheel drive.
- All-wheel drive with automatic connection.
- All-wheel drive with manual connection.
Permanent four-wheel drive
The system, operating on the principle of permanent all-wheel drive, consists of the following structural elements:
- Transmission.
- Transfer case.
- Center differential.
- Clutch.
- Axle driveshafts.
- Main axle gears.
- Cross-axle differentials.
- Wheel axles.
This transmission design can be used regardless of the location of the engine and gearbox (layout). The main differences between such systems are caused by the use of various types of cardan gears and a transfer case.
Principle of operation:
From the engine, the torque is transmitted to the transfer case. In the box, with the help of an interaxle differential, it is distributed between the front and rear axles of the car. So, first, the moment is transmitted to the cardan shaft, through which it is transferred to the main gear gears and interwheel differentials. Through the axle shafts, the differentials transmit torque to the wheels. In the event of uneven movement of the wheels caused by entering a turn or leaving on a slippery surface, the interaxle and interwheel differential locks.
The most famous designs of permanent all-wheel drive transmissions are the Quattro system from Audi, xDrive from BMW, 4Matic from Mercedes.
The Quattro was the first mass-produced transmission with permanent all-wheel drive for sedans. She appeared in 1980. This system is designed for installation with a longitudinal engine. After several upgrades, it is widely used in modern Audi models.
The xDrive system was developed by BMW for use in its own sport utility vehicles and passenger cars. She appeared in 1985. In the latest upgrade, xDrive integrated several modern systems, which turned it into an active transmission.
4Matic is an all-wheel drive transmission developed by Mercedes. It was introduced in 1986. Nowadays, it is installed on several models of passenger cars of a German manufacturer. A distinctive feature is the possibility of using only in combination with an automatic transmission.
All-wheel drive connected automatically
Typically, such a system consists of the following elements:
- Transmission.
- Clutch.
- Main gear of the front drive axle.
- Transfer case.
- Main gear of the rear drive axle.
- Cardan transmission.
- Cross-axle differential of the front axle.
- Coupling for connecting the rear drive.
- Cross-axle differential of the rear axle.
- Half shafts.
The all-wheel drive transmission is the most popular of all all-wheel drive systems. Almost every manufacturer has a model using a similar design. It is well suited for use in passenger cars, as it can provide all-wheel drive when needed, but it costs much less than a permanent all-wheel drive transmission.
Principle of operation:
The all-wheel drive system is activated when the front axle wheels slip. In normal condition, torque from the engine is transmitted to the main axle through the clutch, gearbox and differential. In addition, through the transfer case, the moment is transmitted to the main control element of this system - the friction clutch. In normal straight motion, the clutch transfers only 10% of the torque to the rear axle, and the pressure in it remains minimal. In the event of slippage of the front axle wheels, the pressure in the clutch increases, and it transfers torque from the engine to the rear axle. Depending on the intensity of slippage of the front wheels, the degree of transmission of torque to the rear axle may vary.
The most famous all-wheel drive transmission is the 4Motion system developed by Volkswagen. It has been used in the car designs of the concern since 1998. The latest version of 4Motion uses a Haldex coupling as a working element.
Four-wheel drive, manually connected
In the classic version, the system has almost the same design as the transmission with permanent all-wheel drive.
- Transmission.
- Transfer case.
- Clutch.
- Axle driveshafts.
- Main axle gears.
- Cross-axle differentials.
- Wheel axles.
In modern cars, this type of transmission is not used. This system has a very low efficiency. Its only advantage is that it provides a 50/50 torque distribution between the axles, which is not available with any other type of transmission. Therefore, it is considered ideal for powerful SUVs.
Principle of operation:
The principle of operation of the transmission with manual connection of all-wheel drive is similar to the system with permanent all-wheel drive. The only thing is that the transfer case is controlled directly from the passenger compartment using a special lever.
One of the most serious shortcomings of the system is the inability to use it for a long period of time. This means that it can be connected temporarily when it hits a slippery or wet surface, but then it should be immediately disconnected. Long-term use of such a transmission leads to an increase in vibration, noise and fuel consumption.
Now a very large number of so-called crossovers have not entirely honest four-wheel drive. It is not permanent, and even connected for a very short time (I would like to note that it is connected automatically) - we will definitely talk about whether this is good or bad in another article, but today I want to talk about “automatic connection” using a “viscous coupling” - and what is it You know? After all, this unit is now very much in demand, but unfortunately many simply do not represent the principle of its operation, although this name is on everyone's lips. Well, as usual, I figured out the topic and will try to tell you in detail what it is and how it actually works, there will be a detailed video at the end, so read on - watch ...
In fairness, I would like to note that viscous couplings are used not only in all-wheel drive systems, but also in car cooling systems and not only. To begin with, as usual, the definition.
Viscous coupling (or viscous coupling) is an automatic device for transmitting torque by means of the viscous properties of special fluids.
To put it simply, the torque is transmitted by changing the viscosity of a special fluid in the viscous coupling housing.
About the liquid inside
At the very beginning, I want to talk about the fluid that is inside the viscous coupling, what it is and what properties it has.
To begin with, I would like to say that they are poured inside - a dilatant liquid, which is based on silicone. Its properties are very interesting, if it is not strongly heated and stirred, it remains liquid. BUT if you mix it a lot and heat it up a little, it thickens and expands very much, it becomes more like a hardened glue. After mixing again becomes insignificant, it again acquires its original state of aggregation, that is, it becomes liquid.
It should be noted that the liquid is filled for the entire service life of this unit and is not subject to replacement.
Device and principle of operation
It's very much like an automatic transmission's torque converter, if you will, where torque is transmitted by oil pressure. Here, too, the transmission of torque occurs due to the liquid, but there are global differences in the principle of operation.
There are only two main viscous devices:
- There is a closed hermetic housing in which two turbine wheels with impellers rotate opposite each other (sometimes more), one is mounted on the drive shaft, the other on the driven one. Of course they rotate in our dilatant fluid. As long as the shafts rotate synchronously, there is practically no mixing of the liquid. BUT, if one axle stands up and the other rotates very quickly (wheel slip), then the liquid inside begins to mix and heat up very quickly, which means it thickens. Thus, the first driving impeller engages with the driven impeller and begins to transmit torque to the second axis. After the car has coped with off-road, mixing stops and the rear axle is automatically switched off.
- The second design also has a closed body. Only on the driving and driven shafts are several groups of flat discs. Part on the slave, part on the master. They also rotate in a special fluid. While the rotation is uniform, the mixing of the liquid is minimal and it is liquid, but after one axis stands up, the second one starts to slip, the mixing is huge! It not only thickens, but also expands. Thus - very strongly pressing the disks to each other. As a result, the transmission of torque - the second axis begins to rotate.
A viscous coupling is a fairly simple and effective mechanical device, with proper use it can walk without any problems for a very long time.
Where are viscous couplings used?
Actually there are only two main applications, but now there is only one:
- Used for engine cooling. A viscous coupling with a fan was attached to the rod. It was driven from the crankshaft of the car through a belt drive. The faster the engine rotated, the more the liquid thickened and the connection with the fan became stiffer. If the speed dropped, then there was no such strong mixing, which means that there were slippages, that is, the fan rotated, it did not cool the radiator so much. Such a system is effective for the cold (winter) period, when the engine does not warm up much, but it is also cooled. Now the use of such systems on new cars is no longer to be found, it was replaced by electronic fans (with sensors in the liquid), which are powered by electricity and are in no way connected with the engine crankshaft.
- Automatic connection of a full drive. It is in this direction that viscous couplings have remained very much in demand. Practically on 70 - 80% of crossovers or SUVs, such systems are now used. True, they are gradually beginning to be replaced by fully electromechanical options, but so far they are more expensive and not so practical.
On the one hand, a viscous coupling is a very simple, cheap, practical and versatile mechanical device, on the other hand, it has a lot of disadvantages.
Pros and cons of viscous coupling
To begin with, I propose to talk about the advantages of this site:
- Simple construction. Indeed, the design is very banal, there is nothing overly complicated in it.
- Cheap. Due to its simplicity, it is not expensive at all
- Durable. The viscous coupling housing can withstand a pressure of 15 - 20 atmospheres, it all depends on the design. If initially there were no breakdowns, then this means that it can take a very, very long time.
- Practical. WHEN USED PROPERLY. Installed for the entire life of the car, does not require any attention.
- ON a dirt road or asphalt, it can also work. If you say abruptly “started” from a place or there is a slip on ice or dust. Then the rear axle will automatically connect. This gives advantages in handling even in the city.
Despite the advantages of the design, it is worth noting about its shortcomings, because there are also many of them.
- Maintainability. As a rule, it is not repaired, that is, disposable, it is not profitable to repair and it is very difficult for a simple layman. Almost always replaced with a new one.
- Connectivity. There is no linear dependence of the all-wheel drive connection, it is almost impossible to guess when the disks inside will slow down! Therefore, there is no control over all-wheel drive.
- You cannot connect the drive manually yourself.
- Low efficiency all-wheel drive. The transfer of maximum torque will be only when the front wheels will slip very much.
- Large viscous couplings are not used. Because it needs a large body, and since it hangs from below, it really greatly reduces the car's ground clearance. The use of small housings, that is, small viscous couplings, leads to a limited transmission of torque to the rear axle, because there are fewer discs and a small volume of special fluid
- A viscous coupling cannot work for a long time. This is highly undesirable! It is not designed for long-term loads, otherwise it will simply fail, it will completely jam. That is, it tells us that you can’t meddle in serious off-road! Use it as soon as possible for snowy yards and a little dirt in the country, that's all.
Until recently, a huge proportion of buyers around the world preferred cars equipped with a drive on only one axle, referring the category "4x4" exclusively to off-road topics. Now this view is clearly outdated: today all-wheel drive systems have seriously evolved and perform a number of other equally important functions. So, the All Mode 4x4-i system has become "corporate-wide" for most "Nissan" models. Of the 14 cars of the brand offered on the Russian market, including two pickups, 10 are offered with all-wheel drive! X-Trail, Juke, Qashqai, Pathfinder, Murano have a similar transmission ... This does not mean that all elements of car systems are the same - they only have a common ideology. Everything seems to be simple: the rear (in the case of, for example, Qashqai or X-Trail) or the front (Patrol) drive should be connected only if necessary by means of an electromagnetic clutch. But this is just the tip of the iceberg, the main part of which is the various electronic driver assistance systems. Let's start with the fact that the All Mode 4x4-i transmission itself is an ideological continuation of the previous generation with the same name, except perhaps without the "i" prefix, which, in fact, we wanted to dot all over. But first, a brief historical digression.
When drifting, the torque on the rear axle is increased to achieve the desired turning radius. When skidding, the torque on the rear axle is reduced to achieve the desired turning radius
BACKGROUND
The idea of automatically connecting the second axle, in general, is not new: at the dawn of the third millennium, almost all automakers rushed to get rid of classic and completely “mechanical” transmissions in favor of various kinds of automatic systems. For what? One of the main disadvantages is that the constant operation of all-wheel drive inevitably led to increased fuel consumption (we are talking about full-time all-wheel drive). Here the reader should have an iron counterargument: what about SUVs with a switchable front axle with the Part-time system? I do not argue that such a solution really allows you to save fuel, but the car was deprived of another advantage - reliable handling on slippery surfaces. Of course, there is a third type of truly off-road transmission - a hybrid that combines the advantages of Part-time and Full-time (as on the Mitsubishi Pajero or some versions of the Jeep). The compromise is successful, but there are also drawbacks here, the main of which are expensive and cumbersome. Installing a heavy and expensive transmission on a car, which requires some driver training, is extremely absurd in our time - the price of the car and its weight now play far from the last roles. Well, the last argument, which, perhaps, became decisive in the extinction of the era of classic SUVs: they have ceased to be in demand, as the sales results eloquently speak of. The buyer himself made his choice: no one wants to understand the intricacies of off-road piloting, to think about which lock should be activated and whether it should be turned off at all later. Of course, true jeepers exist to this day, but their share is so small that it simply makes no sense for manufacturers to bother with the production of, in fact, piece, voracious and outdated products.
Automatic torque distribution to the rear axle from 0 to 50%
Forced lock mode 4WD Lock
THEORY
They seem to have sorted out the ideology: a modern crossover should have low fuel consumption, remain comfortable and easy to drive under any road conditions, while maintaining a high level of safety and, moreover, justify its purpose, that is, be able to move over rough terrain. It is easy to guess that the "Nissan" All Mode corresponds to all these parameters. What does he represent? Let's look at the example of the new X-Trail. As already mentioned, All Mode 4x4-i is the next stage in the development of the previous generation of all-wheel drive transmission. Conventionally, the system can be divided into several components: a transfer case (essentially a gearbox that combines a front axle differential and a power take-off gearbox for the rear wheels), a rear gearbox, an electromagnetic clutch mounted on its body and a bunch of control electronics. Such a system is currently optimal both in terms of compactness and efficiency. In automatic mode, the torque from the gearbox is transmitted by default only to the front wheels, while the driveshaft is spinning idle, “waiting” for the clutch to close in order to transfer the moment back at the right time. The location of the coupling directly on the rear axle is not accidental. Firstly, this achieves a better distribution of the car's weight between the axles; secondly, the already loaded front end is not cluttered; thirdly, the rear gearbox operates most smoothly and as quickly as possible - it is easier to turn the gearbox gears with an already rotating cardan shaft with a high inertia force than trying to do it “at the beginning” of the path at the front axle. Four-wheel drive, implemented in this way, is much simpler, lighter, and more versatile than "real" off-road designs. It remains to figure out in which cases the electromagnetic clutch should close, and does everything depend on it? This is where the mysterious forces of electronics come into play.
DOTS OVER i
Although, if you look, there is nothing mysterious here: the whole system meets the strict rules of logic and common sense. It is worth starting with the transmission modes: as in the previous generation of the system, the 2WD, Auto and Lock modes (front-wheel drive, automatic mode, locked clutch) have been preserved. In general, the logic of moment distribution remains the same. In automatic mode, the rear wheels come into operation mainly when the front wheels slip, while up to 50% of the torque can be transmitted back. The clutch closing itself depends on the operation of many sensors - steering wheel turn, angular speed, acceleration, wheel speed ... Although the clutch in the rear axle drive can be locked hard by turning on the Lock mode. But here it is worth remembering that movement with a locked "center" (essentially a center differential) is possible only on slippery surfaces - the wheels of the rear and front axles rotate at the same speed, which can adversely affect the transmission elements. That is why, in order to avoid breakdowns, the clutch automatically switches to Auto mode when the car accelerates sharply or if the speed exceeds 40 km / h. As before, the all-wheel drive system actively cooperates with the vehicle's dynamic stabilization system (ESP): in addition to helping with loss of control (drifting or skidding), the system can help off-road. Most characteristically, this manifests itself with diagonal hanging, when ESP slows down the slipping wheels, transferring moment to the stationary wheels. But this electronic assistant is not always needed: to overcome slippery areas, when maximum engine performance is needed, it is recommended to turn off the system.
The main difference from previous generations of the system is the active interaction of the transmission with the integrated Nissan Chassis Control chassis control system. In addition to the fact that, depending on road conditions, the system can automatically transfer torque between the axles, electronics can help you stay on the trajectory with engine braking during the release of gas in a turn or on a straight line. Also, to maintain a predetermined trajectory during cornering, the system separately regulates the braking forces applied to each wheel, compensating for understeer or oversteer. The picture is crowned by the body vibration damping system: if the electronics notice the development of a diagonal buildup, the stern vibrations can be eliminated by a short braking impulse.
PRACTICE
I got acquainted with the upgraded all-wheel drive system back in winter, at the premiere test of the new Nissan X-Trail. We must pay tribute to the organizers - the location for the winter test drive was chosen perfectly. We are talking about a stunning corner of our vast, Karelia, with its extremely diverse roads and their no less diverse absence. The main highlight of the roads, in addition to their ease, is a rather interesting surface: reagents are used here only near large cities, as a result of which the roads are often covered with either rolled snow or an even layer of ice. This is where it becomes clear that good winter tires and competent four-wheel drive are useful things. The first thing that surprised the car was its stable and safe behavior. If I had not been told in advance about the presence of a vibration damping system, I would hardly have paid attention to it - it so imperceptibly and unobtrusively extinguished the diagonal buildup of the car. The actions of All Mode 4x4-i, coupled with Chassis Control, especially manifested themselves on bare ice: you enter a turn at a decent speed and you know exactly what will definitely carry you out ... And someone pulls the Nissan back into the inside of the turn with invisible threads. Awesome! To fill the "X-Trail" in a dashing skid, you need to try very hard, turning off the ESP system first. Ten years ago, an ordinary motorist could not even dream of such a thing - an extremely predictable behavior! Summing up, we can safely say that the efforts of the developers were not in vain - it became really easier to drive a car.
