Golf closes the gasoline/diesel gap, loses mass, and gains 'premiumness'

  • 09-Nov-2012 04:16 EST
VW10-12 Golf b.jpg

C-pillar and roofline treatments are established signatures of the Golf and continue with the Mk. VII that sits on the VW Group's standardized but versatile MQB platform. 

“This is an all-new car – new chassis, new engines – everything,” says Stefan Jung, Technical Project Manager for the Volkswagen Golf Mk. VII. “Maybe a few screws are the same as those used on the previous car but that’s about all!”

VW chose Sardinia for the media launch of the new car; a venue that combines the sort of roads on which to convincingly demonstrate the car’s MQB (Modularer Querbaukasten) modular transverse matrix platform designed not only to be applicable to a wide range of vehicle types across the Volkswagen Group (Polo to Passat for the VW brand) and having a high carry-over of parts but to bring “fundamental changes” to ride and handling standards.

Although longer than its predecessor by 56 mm (2.2 in) to 4255 mm (167.5 in) overall, wider by 13 mm (0.5 in) to 1799 mm (70.8 in), lower by 28 mm (1.1 in) to 1452 mm (57.2 in), and on a 59 mm (2.3 in) longer wheelbase at 2637 mm (103.8 in), it is lighter by up to 100 kg (220 lb) and is up to 23% more fuel-efficient. Its gasoline engines have started to become convincing rivals of diesels in terms of performance, fuel consumption, and CO2 emissions.

Most of the mass saving has been via the engines at 40 kg (88 lb), superstructure at 37 kg (82 lb), and running gear at 26 kg (57 lb), while 6 kg (13 lb) was also taken out of the electrics. The air-conditioning is lighter by 2.7 kg (6 lb) via such areas as optimized wall thicknesses of components and reduced diameter of pressure lines. A new thermoplastic injection process took 0.4 kg (0.9 lb) out of the dashboard’s mass.

The new Golf is also better equipped, with an even greater accent on cabin “premiumness.” Mass has been controlled without the extensive use of aluminum, magnesium, or carbon fiber.

“In this class, we have to look particularly at cost, so we have achieved much of the savings needed by using different steels,” explained Jung. “We are also achieving weight saving with intelligent processes like hot forming, allowing thinner steel to be utilized without losing structural strength. Presses reach 930°C (1706°F) for A- and B-pillar outers and other areas. Other manufacturers use this, but not at our volumes—around 2000 cars a day."

Already torsionally stiff at 25,000 N·m (18,400 lb·ft) per degree in Mk. VI form, the new car achieves 27,000 N·m (19,900 lb·ft) per degree. The body structure is 23 kg (51 lb) lighter.

Production of the Golf has reached 29 million units over 38 years and, like the versions that have gone before, the Mk. VII is an unapologetically evolutionary design. It is immediately identifiable as a Golf, although every panel has been changed. There is a prominent crease line that runs around the car, and the hood is now more convex than concave to improve pedestrian safety by opening up more space above the engine bay’s hardpoints without recourse to an active hood system.

The Golf Mk. IV’s C-pillars and wheel arches and the Mk. I’s roof line remain enduring styling signatures. The design teams were led by Walter de Silva as the VW Group design boss and Klaus Bischoff for the VW brand.

As ever, safety is a high priority. The new car incorporates a multicollision braking system that automatically brakes the vehicle after an impact to reduce kinetic energy and the possibility of a second impact. A PreCrash system, which pretensions seat belts and almost fully closes windows and sunroof to optimize overall airbag effectiveness, is also available to detect and take action to avoid or minimize the effects of a crash. VW is targeting a five-star EuroNCAP rating for the new Golf range. The MK. VI achieved the figure.

However, it is the powertrain and chassis technologies that dominate the Golf Mk. VII story—not only those available initially but also those that will be coming. Of particular note is the coming BlueMotion TDI turbodiesel 1.6-L 81-kW (109-hp) version with an output very close to that of the original gasoline GTI and a fuel consumption of 3.2 L/100 km and CO2 emissions of 85 g/km. The theoretical range of the car is 1562 km (971 mi). VW Group CEO Prof. Dr. Martin Winterkorn describes it as “the most fuel-efficient Golf ever.”

Dr. Ulrich Hackenberg, VW Board Member for Technical Management, added that the new Golf fleet, having reduced emissions by 13.9%, will produce 119,000 tons less CO2 annually in Europe alone.

But performance versions will still play a significant role; the new GTI generation will have a 2.0-L 162-kW (217-hp) turbocharged gasoline engine with peak torque of 350 N·m (258 lb·ft)—70 N·m (52 lb·ft) ahead of the Mk. VI’s figure.

VW is taking the downsizing of engines very seriously, and an idea of what is being achieved can be gained by comparing the Golf’s power, torque, and combined fuel consumption figures of its new aluminum-block 1.4-L 103-kW (138-hp) turbocharged gasoline unit with the 2.0-L 110-kW (148-hp) turbodiesel. Each has a manual six-speed gearbox as standard.

The engine benefits from ACT cylinder deactivation, with the engine running on two cylinders at light loads and cruise from 1400 to 4000 rpm, saving around 0.5 L/100 km of fuel burn. The gasoline unit returns 4.8 L/100 km and 112 g/km, the diesel 4.1 L/100 km and 106 g/km. In DSG (twin-clutch automated manual) form, the gasoline engine’s CO2 reduces to 110 g/km, but the diesel’s rises to 119 g/km, with the former's fuel consumption dropping to 4.7 L/100 km and the diesel’s rising to 4.5 L/100 km. However, the gasoline model's DSG is a seven-speed unit and the diesel’s is a six-speed.

The gasoline engine is remarkably turbine-like and smooth in its operation across the rev range. Engine mounts have been optimized but continue to use a pivot bearing system.

VW is now using a low-friction toothed belt to drive overhead camshafts. It is 20 mm (0.8 in) wide and has load-reducing profiled belt wheels. It is engineered to achieve a service life equal to that of the car. Valve drive actuation is via roller cam followers, and there is an anti-friction bearing for the highly loaded first camshaft bearing, which also helps reduce friction.

As for the MQB chassis, which is already used by the Audi A3 and previously described by AEI (see, what VW terms “proven components” were developed further to conform to the Golf’s requirements.

The rear suspension developed for engine versions below 90 kW (121 hp) has a mass of 38 kg (84 lb). For higher powered Golf applications, it comes in at 48 kg (106 lb). Design changes at the rear include connections of the tubular anti-roll bar within the suspension, which improves packaging. Some 4 kg (9 lb) was saved by structural optimizations and the use of high-strength steel.

At the front is a MacPherson strut layout. All components again were reworked to achieve functionality, weight, and cost targets. Mass saving, even without using aluminum (high-strength steel was used for the transverse links), is 1.6 kg (3.5 lb).

Hybrid- and pure-electric versions of the Golf are in development.

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