VW's fuel-efficient gearbox

Volkswagen has added a fuel-efficient, seven-speed semi-automatic gearbox to its Golf and Golf Plus ranges.

The gearbox is a development of its direct-shift gearbox (DSG), which works by using two clutches to pre-select each gear, thereby cutting gearshift time and making the car more efficient.

Fuel savings over the existing six-speed DSG unit are possible because the gearbox has an efficient clutch arrangement that loses less of the engine's power, is 23kg lighter and has a longer top gear to reduce motorway fuel consumption.

How much does it save?
Tests show that cars fitted with the gearbox emit up to 20% less carbon dioxide per kilometre than cars fitted with a standard automatic gearbox and up to 12% less than cars fitted with a standard manual gearbox.

The fuel savings are far greater when the gearbox is linked to petrol engines, however. VW says this is because the efficiency of its diesel range is already much more advanced than its petrol range.

In a Golf fitted with a 119bhp 1.4-litre TSI engine, this means fuel economy improves from 44.9mpg to 47.8mpg when comparing the six- and seven-speed DSG gearboxes. Similarly, carbon dioxide emissions fall from 149g/km to 139g/km.

Which cars will get it?
The seven-speed gearbox can be linked to petrol or diesel engines ranging from 102bhp to 167bhp and with pulling power of up to 184lb ft.

That means it will be sold on models ranging from the Polo to the Passat.

The seven-speed gearbox is also fitted with a hill-start system, which is activated by pressing the brake once. It disengages when the throttle is applied.

When can I buy it?
The Golf and Golf Plus models fitted with the seven-speed gearbox are available now, while it should be available in the Passat this summer and the Passat CC when it is launched later this year.

On average, the seven-speed DSG gearbox costs 1300 more than the standard manual equivalent, with the entry-level 119bhp 1.4-litre TSI five-door Golf S costing from 15,982.

The existing six-speed DSG unit, meanwhile, will continue to be offered on models ranging from the Golf to the Passat that require more pulling power. The characteristics of the six-speed unit make it ideal for use with engines that have between 184lb ft and 258lb ft of pulling power.

The future
The seven-speed gearbox has been built to be compatible with start-stop technology and hybrid engine systems, so it opens up new avenues of emissions savings to VW.

Furthermore, insiders admit that the gearbox is under consideration for installation on future Bluemotion models. Combined with stop-start technology, estimates suggest a car that emits less than 90g/km of CO2 is immediately achievable.

However, fears that the gearbox could make the cars too expensive could mean that its introduction is delayed.

Similarly, the seven-speed gearbox is unlikely to be sold on cars equipped with VW's four-wheel-drive system, because there are unlikely to be enough customers to make it economically viable.

In the short-term, the addition of more gear ratios to eke out more efficiency is more likely. Senior VW gearbox technicians concede that anything up to a nine-speed gearbox could be fitted into cars in their current configuration.

Longer-term, VW has already started road-testing a hybrid system. With the seven-speed gearbox linking easily with that technology, expect a large hybrid VW to go on sale in the USA and Japan within the next three years.