New Golf will draw efficiency lessons from VW's 313mpg XL1 two-seater; set to go on sale in 2019
17 August 2014

Work has started on a package of aerodynamic innovations for the next generation of Volkswagen Golf, according to company sources. 

The Mk8 Golf, which is due in 2019, will have to be one of the most economical mainstream cars ever built. VW engineers and designers have already started to investigate ways of reducing the average CO2 output of the next range of Golf models to well below 90g/km.

It is understood that VW will be using the lessons learnt from the radical two-seat XL1, which makes extensive use of aerodynamic innovation to help it achieve 313mpg. 

The fact that early work is already under way on a car that is still at least five years from the showroom indicates the hurdles that face all car makers in meeting the European Union’s rigorous fleet-average CO2 emissions standards, which come into force in 2020. 

Although VW sells proportionally far more Golfs and Polos in Europe than it does bigger and less economical vehicles such as Passats and Tiguan SUVs, figures supplied by the EU suggest that VW – along with most other European car makers – will still have to reduce the average CO2 output of its future fleet by between 
22 and 27 per cent. 

Given the need for such a significant reduction in average fuel consumption, VW engineers are unlikely to be able to just bet on another round of engine improvements, instead, they are likely to need to exploit every new trick in the book, including the most advanced aerodynamic treatment yet seen on a production vehicle.

According to a VW insider, “a number of aerodynamic solutions are being investigated [for the Golf Mk8]”. However, according to the source, a fundamental difficulty facing the engineers and designers is that, proportionately, the Golf is quite a short car.

The XL1 has been shaped primarily for aerodynamic efficiency so it is both low and long. However, the Golf, by definition, is a family-size hatchback and that effectively sets the car’s proportions.

VW also has to consider that mainstream buyers may not want a car that loses its character to the demands of cutting-edge aerodynamics. 

For example, the sharp-edged rear corners of cars such as the Toyota Prius and Chevrolet Volt improve the way that the airflow ‘breaks off’ the body, but they could probably not be used for the Golf Mk8. However, one solution could be to extend the hatchback’s rear spoiler further over the rear window, along with deep blade-like extensions along the upright sides of the window.

The Golf Mk8 will be based on the MQB platform and be built from conventional stamped and welded panels. This means that the car will be no wider or longer than today’s Mk7 Golf. However, VW will have to find further weight savings in the new car, bringing the base kerb weight under 1100kg.

It seems unlikely that VW will invest in aluminium for any of the Golf 8’s exterior panels, because cost control will also be a major issue for the new car. With the likely addition of complex new technology, keeping the factory build cost down is of paramount importance.

Meeting the impending 
CO2 regulations, which will almost certainly add hundreds of euros to the cost of building a car, could prove devastating for many mainstream car makers that are surviving on very slim profit margins.

New Golf's fuel-saving tech

Flywheel

Volvo is already testing a British-designed flywheel system, which is used to drive the rear wheels of a front-drive car.

Flywheels could become familiar on mainstream cars in the next decade because they can store waste energy and release it like an electric motor and battery. Flywheel systems are about a quarter of the cost of a hybrid set-up, far less complex and far lighter.

Volvo’s system takes 8.0sec of braking to recharge and offers 10sec and 80bhp of drive assistance. A future Golf would likely use a unit good for 40bhp or so. 

Variable compression ratio engines

Earlier this year, Audi technical chief Ulrich Hackenberg announced that the Volkswagen Group was developing engines with variable compression ratios.

Hackenberg didn’t reveal any details about how this will be executed, but the principle has long been an important goal for engine designers. Being able to vary an engine’s compression ratio depending on the demands being placed on it should lead to significant advances in efficiency. 

Coasting

Audi’s Ulrich Hackenberg also said that coasting technology would be used in future VW Group models. Coasting technology is expected to be rolled out in three stages. The first stage – coasting at speed – is already featured on some VW dual-clutch ’boxes.

The next version is expected to function when the car is travelling below 4mph. The ultimate version will allow transmission decoupling and engine shut-down when cruising at speed, travelling downhill or approaching traffic lights that are about to turn red. 

Electric turbochargers

Audi has already previewed its own version of electric turbocharging, which uses a powerful fan in the engine’s induction system.

This blows air through the turbo when the engine is decelerating, spinning the turbo fan up to speed, so that full boost is available as soon as the driver gets back on the accelerator.

Such a system is especially useful for downsized engines, which generate little exhaust gas energy, especially at low speed. A future Golf with, say, a 1.0-litre three-pot would have much improved driveability characteristics.

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17 August 2014
The 2nd paragraph highlights the wrong direction both manufacturers and government have been heading in. CO2 should not be used as a value of eco advancement. It should be pollution based on harm or toxicity to life. I was hoping this would change by 2019.

18 August 2014
With increasing congestion and punitive speed limits, improved aerodynamics will be of limited effectiveness. By contrast a weight savings would yield much more benefit both on the road and during production and eventual recycling of the vehicle. And let's not forget it is especially important in EU fuel test cycle which is current yardstick for CO2 measurement. If VW is genuinely serious about low drag, then this really should take priority over styling considerations, and a future Golf should incorporate features like a cut-off tail, rear wheel fairings and the like.

18 August 2014
LP in Brighton wrote:
If VW is genuinely serious about low drag, then this really should take priority over styling considerations, and a future Golf should incorporate features like a cut-off tail, rear wheel fairings and the like.
That could work on the Golf as they are largely sold off from their badge and the name. I think many people buy a Golf to make a particular statement (although what they intend to demonstrate is the opposite of what i think when i see someone drive a Golf) and having eco credentials would make the statement that they're concious about the effects of pollution on the world and blah blah. However, that wouldn't work for its sister brand SEAT, because it sells on the principle that cars are and have always been emotionally purchased products ever since it took over the role of a horse. Creating an interesting and beautifully styled affordable car for people who would otherwise have to spend £100k + on a supercar and a family car is what it offers to its customers, and these measures would destroy its usp. I think on the whole people need to take responsibility for how they use their cars, but that would never be the case. Governments need to take more action by making it difficult for drivers to drive in cities (where most of the world's pollution is created) and making it cheaper and easier for people in public transport. Its not enough to get manufactures to build more eco friendly cars especially when you consider that roughly 70% of us will be living in mega-cities by 2025. Banning irresponsible car use from cities is the only solution in my opinion.

18 August 2014
For far too long now cars have been getting fatter and taller. All car makers need to start building cars smaller, lower, lighter and more slippery. Some progress has been made on weight reduction but, too little and no real progress on drag reduction with small cuts to the Cd offset by increasing frontal area.

 

I'm a disillusioned former Citroëniste.

18 August 2014
What exactly are we talking about here? The XL1's exorbitant price? Its ground-breaking 2-pot diesel engine? Its impracticality? Its outlandish looks? Other than outlandish looks, surely the Golf couldn't possibly gain from the VW's failed XL1 experiment.

18 August 2014
I'd like to know more about how the coasting technology works. I can see the benefits on long flat sections of road, but in hilly areas I like to use engine braking as much as possible so this coasting technology concerns me a little. Also, how would it be integrated with the flywheel idea? Personally, I think plug in hybrids are the best solution at the moment and look forward to the Golf version soon.

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