| Fifth-generation Haldex coupling in the Golf 4MOTION. Click to enlarge. |
Volkswagen is expanding the new Golf range with versions with 4MOTION all-wheel drive. In this latest version of the Golf 4MOTION, Volkswagen is using a four-wheel drive system with an enhanced, fifth-generation Haldex coupling.
Volkswagen is offering the new Golf 4MOTION in Europe in three levels (Trendline, Comfortline, Highline) and with two turbo diesel engines. The Golf 1.6 TDI 4MOTION BlueMotion Technology delivers 77 kW/105 PS and consumes 4.5 liters per 100km (52.3 mpg US). The Golf 2.0 TDI 4MOTION BlueMotion Technology delivers 1010 kW / 150 PS with fuel consumption of 4.7 liters per 100km (50 mpg US). The new model consumes 0.8 liters or 15% less fuel than the current Golf 4MOTION delivering 150 PS.
| Golf 4MOTION. Click to enlarge. |
The Golf 4MOTION’s four-cylinder diesel engines (EA288) are new designs, and made their debut in 2012 with the Mk 7 Golf. Many of the components are used by virtue of the new modular diesel engine system (MDB). These include components of relevance to exhaust emissions, such as the injection system, the turbocharger and the intercooling within the air intake module. Exhaust gas recycling with cooled low-pressure EGR is also used.
Another new feature on the Golf’s TDI engines is the proximity of the components for the after-treatment of exhaust gases to the engine. Also on board: oxidation catalytic converter, diesel particle filter and NOx adsorber catalyst.
Maximum power from the 1.6L engine is produced between 3,000 and 4,000 rpm, while the maximum torque of 250 N·m (184 lb-ft) is available from a low 1,500 up to 2,750 rpm. With this TDI engine the Golf 4MOTION accelerates in 11.5 seconds from 0 to 100 km/h and achieves a top speed of 187 km/h (116 mph).
The Golf 4MOTION’s 2.0-liter TDI produces its highest output between 3,500 and 4,000 rpm, with its maximum torque of 320 N·m (236 lb-ft) being available from just 1,750 (up to 3,000) rpm. The Golf 2.0 TDI 4MOTION with BlueMotion Technology has a top speed of 211 km/h (131 mph) and accelerates from 0 to 100 km/h in 8.6 seconds.
Like the front-wheel drive versions the new 4MOTION models are equipped as standard with a Stop/Start system and battery regeneration. Also included as standard even on the base version (Trendline) are features such as the four-wheel EDS (electronic differential locks on both axles), the XDS front and rear axle transverse lock, the electronic stabilization programme, an Automatic Post-Collision Braking System, seven airbags, daytime running lights, air conditioning, electric windows front and back, a multi-function display (on-board computer) and a TFT display with touchscreen operation.
AWD. In 2009, VW chose Haldex as its supplier of AWD technology to be part of their new modular platform; the order was worth SEK 4.5 billion (US$701 million) over 7 years, and was the largest single contract of the Haldex Group.
The fifth generation Haldex coupling was developed to meet future market requirements on weight, cost and fuel consumption.
Haldex currently supplies several major OEM:s, Volkswagen, Audi, Skoda, Seat, Bugatti and Lamborghini. Volvo, Ford Motor Company, Land Rover and General Motors with proprietary and advanced systems and solutions for All-Wheel-Drive Systems.
The intelligently controlled 4MOTION drive weighs 1.4 kilograms less than the previous system, requires no pressure accumulator and reacts extremely quickly to every conceivable influence exerted on it. The result is greater active safety and improved handling.
The Golf’s 4MOTION system uses an advanced control function based on driving conditions. When under a relatively low load or when coasting, forward drive comes primarily from the front axle, with the rear axle decoupled. This basic setting saves fuel. If needed, however, the rear axle is seamlessly engaged. This is done by the Haldex coupling, activated via an electro-hydraulic oil pump.
A control unit permanently calculates the ideal drive torque for the rear axle and regulates via activation of the oil pump the extent to which the multi-plate clutch should be closed. The contact pressure at the clutch plates rises in proportion to the desired torque at the rear axle. The amount of torque that is transferred can be varied continuously using the level of pressure applied to the clutch plates. Even when driving off and accelerating quickly, the wheels of the Golf are prevented from spinning, as the control unit regulates the torque distribution in line with the dynamic axle loading.
Activation of the Haldex 5 coupling is based primarily on the engine torque demanded by the driver. In parallel with this a driving status identification system within the four-wheel drive control unit assesses parameters such as the wheels’ speed of rotation and the angle of turn. Almost 100% of the drive torque can be directed to the rear axle, as required.
When maneuvering or going around tight corners any build up of pressure on the drive train is avoided by reducing the torque exerted on the Haldex coupling. The opposite happens in the event of heavy and rapid acceleration. In this case the coupling torque is increased with corresponding speed. Meanwhile, at high speeds the pre-control of the coupling, which is based on engine torque, is disabled in order to minimise fuel consumption. In this case front-wheel drive dominates.
However, even in this situation 4MOTION remains a permanent all-wheel drive system, as the rear axle is instantly re-engaged as soon as any slippage registers on the front axle or the Golf is driven with increased lateral acceleration.
In parallel to the Haldex coupling, which acts as an inter-axle lock, the electronic differential locks (EDS) integrated into the electronic stabilization program take on the function of transverse locks. They ensure that if a wheel starts to spin the drive power is directed to the wheel on the opposite side within fractions of a second. While due to the design of the system the front-wheel drive Golf is fitted with EDS on the front axle alone, on the all-wheel drive Golf 4MOTION the electronic differential locks are used as so-called four-wheel EDS on the rear axle as well.
The new Golf 4MOTION is also equipped on the front and rear axles with the additional XDS function, which during fast cornering slows down the wheels on the inside of the bend, thus optimizing steering. In technical terms the XDS is an extension of the function of the electronic differential locks. When the car is being driven fast, as soon as the electronics detect any excessive easing off of the load on either of the wheels on the inside of a corner, the hydraulics of the electronic stabilisation programme systematically apply brake pressure to this wheel to restore optimal traction. The XDS thus operates as a transverse lock differential that compensates against any understeer during fast cornering.
The combination of EDS and XDS systems and a rear axle seamlessly engaged via the Haldex 5 coupling endows the Golf 4MOTION with significant enhancements in terms of safety and handling; it also makes a good towing vehicle (up to 1,700 kg braked towing capacity up a 12% incline).
Vehicles with four-wheel drive place unique demands on occupant safety in head-on collisions. This is because the drive shaft’s effect as a strut between engine and rear axle generally has to be reduced in order to achieve optimum levels of deceleration. In the past this was achieved via very elaborate constructions inside the front tube of the drive shaft.
With the introduction of the Modular Transverse Matrix, the Golf now features an innovative central joint in the drive shaft that both increases safety in the event of a crash and reduces weight. In a head-on impact the drive train’s front tube pushes itself into its rear tube, driving in the process through a central bearing and the central joint and thus optimizing the levels of deceleration.
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