Analysis of the transmission system of Volkswagen's seventh-generation Golf GTI

    The appearance of Volkswagen's seventh-generation Golf GTI is not much different from the sixth-generation Golf GTI, except that the sixth-generation's rounded lines have become sharper, which can easily be mistaken for an upgraded model. But in fact, the two are very different. The most obvious point is that the sixth-generation Golf is designed and manufactured on the Volkswagen PQ35 platform, while the seventh-generation is designed on the latest MQB platform.

    The former features: 4-wheel independent suspension, front McPherson type/rear four-link type; long-length laser seamless welding; double-sided galvanized high-strength steel plate, etc. The latter has greater flexibility, which is more conducive to the targeted installation of power systems on the same platform according to different vehicle usage environments around the world. Whether it is traditional power, electric and renewable energy power, or gasoline engine, diesel engine, hybrid system, pure electric system, natural gas engine, biofuel engine, etc., they can all be installed on the MQB platform. In addition, the MQB platform can also adjust the wheelbase, track, front overhang and rear overhang.

    The seventh-generation Golf GTI will be the first Volkswagen brand model based on the MQB platform. Its chassis hardness has been increased and its weight has been reduced. Its sporty performance is further reflected in the suspension and 2.0-liter EA888 engine.

    The seventh-generation Golf will be equipped with two configurations: a 6-speed manual transmission and a dual-clutch transmission. The fuel economy of the former is improved by 18% compared to the previous generation, while the latter is improved by 14%.

    For the US market, the seventh-generation Golf GTI will be 55 pounds lighter than the previous generation. From the outside, its body length and width are 55 mm and 13 mm longer, respectively, and the height is reduced by 27 mm. The frontal area of ​​the car is also reduced from 0.73 square meters to 0.72 square meters.

Powertrain

    In terms of power, it is equipped with the EA888 engine, whose exhaust manifold is integrated inside the cylinder head, providing water-cooled exhaust gas recirculation and achieving faster coolant heating.

    The advantage of water-cooled exhaust gas recirculation is that it does not consume extra fuel to reduce the temperature of the exhaust gas entering the intake manifold, thereby further reducing the effect of nitrogen oxides. However, the disadvantage of the water-cooled exhaust gas recirculation system is that the maintenance cost will increase during the later maintenance.

    The engine uses a turbocharger from IHI Heavy Industries, Ltd., Japan, which provides an intake pressure of about 1.2 bar and a compression ratio of 9.6:1. The compression ratio of 9.6:1 is not high compared to other direct injection engines today, but its maximum power can reach 217 horsepower (162 kilowatts) and its peak torque reaches 350 Nm (258 lb-ft). Its 1-4, 2-3 cylinder matching strategy can effectively prevent the ignition pulse interference in other cylinders.

    The engine uses variable cam timing, with a 60° range for the intake cam and a 30° range for the exhaust cam. The intake valve has two lifts, while the exhaust valve lift is fixed. According to the engineers, the benefits of variable exhaust valve lift are too small compared to the increased cost, so variable exhaust lift is unnecessary.

    Without the performance upgrade kit, the GTI accelerates from zero to 100 km/h in 6.5 seconds and reaches a top speed of 246 km/h. With the kit, the 0-100 km/h acceleration time is shortened by 0.1 second and the top speed can reach 250 km/h.

Chassis and handling

    Another part of the performance package is an electronically controlled Haldex differential lock, which works together with the variable-pitch steering rack and XDS dynamic stability control software to provide the GTI with more agile steering and make up for the understeer defects of front-wheel drive cars.

Steering rack with dense center and sparse ends

    The variable-pitch steering rack has denser teeth in the middle and less teeth towards the ends, which results in a maximum steering range of 380° for the seventh-generation Golf GTI, compared to 500° for the previous generation, meaning the new Golf has a wider steering ratio and more sensitive steering. In addition, there will be no sudden oversteer near the steering wheel's rotation limit.

    Designers adjusted the timing of the intervention of the electronic stability control software to a later time, so that the driver can experience the sportiness of the GTI to the greatest extent. The electronic stability differential lock is also newly added to the seventh-generation Golf GTI. When turning, the rear wheel brakes will automatically brake with appropriate force to reduce the turning radius of the vehicle when turning, and the driver does not need to turn the steering wheel too much.

BorgWarner Haldex locking differential

    The electronic stability control system monitors wheel speed, vehicle speed, yaw rate, lateral acceleration and other parameters at any time to adjust the differential lock to maintain vehicle stability. The multi-plate clutch unit is connected to the differential gearbox through the right half shaft, and an electric pump controlled by the vehicle computer applies corresponding locking pressure to the axle.

    The differential lock can directly provide a locking torque of up to 1,600 Nm to the wheels. In addition, in certain emergency situations, all the torque can be distributed to a single wheel through the locker. During normal steering, the torque will basically be distributed to the outer front wheel to ensure adequate steering.

Electronic auxiliary equipment

    The seventh-generation Golf GTI is equipped with adaptive cruise control, front collision warning, emergency braking, lane keeping, parking assistance and other systems. In addition, the seventh-generation Golf GTI is equipped with a DynAudio sound system.

    The optional performance upgrade kit can increase the engine's maximum power by 10 horsepower to 227 horsepower. In addition, the kit also affects the ignition timing but does not affect the engine's torque.