How can you benchmark a vehicle that has itself become a benchmark in a particular automobile category? The obvious answer is: you benchmark one Golf against another! So, we have been taking a look at the VII, the VI and the V series. A preliminary verdict is that the new Golf has got heavier. A more thorough investigation reveals that the proportion of plastic is now slightly higher than in its predecessors. Polypropylene (PP) continues to be the dominant material, although, here and there, we find polyamide (PA) being used instead of PP.
Volkswagen Golf: seven generations (photo: VW)
Golf VII (photo: VW)
For the VII and the VI series we had a look in each case at the 2l diesel variant and the 1.4l petrol version. For the series V, only the 1.9l diesel was available. The diesel variants are without exception heavier, so we concentrated on these; we paid attention to the petrol versions only where we noticed major differences. As always, we only investigated the plastic parts that we were able to locate directly. We did not examine the tyres, the carpets or the plastic in the on-board electrics.
Despite everything, the overall weight has again increased. While versions V and VI weighed in at approximately 1,350kg, it must have been 1,440kg where the current Golf is concerned.
Polymers breakdown (weight specifications in kg) (source: A2Mac1)
* percentage of overall weight
In the Golf V we found 150kg of plastic, that is 11% of the overall weight. In the Golf VI, plastics amounted to 126kg, representing 9.4%. The new Golf has 142kg or 9.9%.
PP is the dominant material within the material mix. In the Golf V it amounted to 76kg, a figure that has now fallen to 63kg in the Golf VI. The current model uses more than 73kg of PP. The amount of PA used is consistently less. In generation V, PA was around 16.6kg, which fell to 15.1kg in generation VI. The current figure for the Golf is 0.4kg less. A somewhat surprising outcome considering that VW have replaced PP with PA at some points.
PP GF30 front end carrier of the Golf VI (photo: A2Mac1)
PA6 GF40 front end carrier of the Golf VII (photo: A2Mac1)
There is an even bigger surprise (from a plastics point of view) in the front end carrier. Here, VW have replaced the PP GF30 carrier with metal sections to produce a purely PA6 GF40 carrier. Although the carrier has become smaller and looks significantly more elegant, plus it has no metal parts, the weight has remained almost the same. The PP variant based on the Golf VI is, at 2.7kg, only 0.1kg heavier than the PA version. Judging by the peripheral constraints, a significantly higher saving might have been expected, especially in view of the fact that the new version no longer features any metal parts. Nevertheless, a sheet metal section is still necessary to absorb the impact forces.
Dashboard Golf VI (photo: A2Mac1)
Dashboard Golf VII (photo: A2Mac1)
Similarly astonishing is the increase in weight on the dashboard. The Golf VI came in at less than 8kg, but on the latest Golf, it is already 8.8kg – almost 1kg more – although the design is very similar. On both versions the material for the carrier structure is PP GF20.
Pedal system Golf VI
Pedal system Golf VII
However, we were also able to identify assemblies where the weight has actually gone down. In the case of the pedal unit on the Golf, a weight reduction of more than 20% has been achieved.
Generation VI had inherited the pedal unit almost unchanged from Generation V. So it was high time for Volkswagen to come up with a completely new design. When it came to the clutch pedal made from PA, the precision work paid for itself (minus 0.1kg). The brake pedal stayed in steel but was nonetheless 0.2kg heavier. In the case of the accelerator pedal, they wasted no time: a 0.25kg, lightweight PA design emerged from the 0.4kg, heavyweight PP design. And, when it came to the support, it was out with the steel and in with the PA (minus 0.2kg). This meant that the entire pedal mechanism weighing 2.6kg was reduced to a fraction over 2kg.
It would have been a good thing from the point of view of overall weight if the engineers from Wolfsburg had focused on weight optimising all the assemblies and sub-assemblies in this way. But there is still time to do something about that. Generation VIII is already on the drawing board.
Benchmarking products
Instrument panel with MuCell
By creating the instrument panel structure for the new VW Golf VII using microcellular foam, Volkswagen engineers have succeeded in reducing weight by 500g versus the prior model of the Golf. The VW Golf VII is the second vehicle with the instrument panel using the MuCell process, joining the Ford Escape/Kuga IP.
The MuCell microcellular foam technology from Trexel is a complete process and equipment technology that is said to enable the production of high quality plastic parts with enhanced dimensional stability, lower weight/material and reduced cycle time. MuCell technology involves the introduction of precisely metered quantities of atmospheric gases (nitrogen or carbon dioxide) in the plasticizing unit of an injection moulding machine to create a microcellular material structure in the end product.
www.trexel.com
One-piece, U-shaped PC panel for panorama tilt/slide sunroof
The glass surface of Webasto’s electrically-operated panorama tilt/slide sunroof is more than twice as big as a traditional sunroof. The special feature of the sunroof is that it is enclosed in a one-piece, U-shaped panel that boasts a deep black gloss effect and a glass-like, scratch-proof surface. Made of a grade of Makrolon 2605 polycarbonate (PC) from Bayer MaterialScience, optimised specifically for this application, the panel is said to make the glass surface appear bigger and also to hide the bodywork structure, while at the same time serving as a spacer for the side section.
The panel is coated with a new polysiloxane wet-coat system from Momentive Performance Materials that is based on the AS 4700 topcoat used in the series production of Makrolon automotive glazing and the new primer SHP 470FT 2050. This solution claims to offer improved weathering resistance over previous systems, particularly with dark and black PC components.
With a front section that is 1,140mm long and two sides each measuring 980mm, the panel is big for an injection-moulded part – that is why it is produced by injection-compression moulding. This is also the process of choice for manufacturing large, 3D glazing components for panorama roofs using PC, because it produces low-stress components that are free of sink marks, have good surface properties and are easy to coat.
www.webasto-group.com
