You might think, having test-driven a Volkswagen Golf GTI DSG for a few days, that I would be telling you how thrilling it is to experience a 200hp (147kW) engine, in a relatively small car. However, as a Transmission Analyst with CSM Worldwide, I am actually more interested in the letters ‘DSG’, than in the letters ‘GTI’.
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DSG is Volkswagen’s terminology for their Dual Clutch Transmission (DCT) technology, although Audi has recently re-branded the technology ‘S-Tronic’, when used in their vehicles. To date, the Volkswagen Group, including the Volkswagen, Audi, SEAT and Skoda brands, is the only company to have offered road cars with a DCT
With the exception of the Bugatti Veyron supercar, which uses a 7-speed DCT supplied by Ricardo, all DSG units are all built in-house by Volkswagen, at their Kassel plant in Germany. Known internally as the DQ250, the ‘250’ would usually indicate a torque rating of 250N.m, but in this case the logic is not followed, with the unit actually capable of 350N.m, and possibly even c.380N.m by 2007.
So, what of my experiences of this 6-speed DCT in the Golf GTI? What follows is a brief review of the 3 different modes in which it can be operated: Automatic-Drive, Automatic-Sport and Manual.
But before I talk about the transmission, I have just one comment to make about the engine, impressive as it is. At idle there is, dare I say it, a slight whiff of diesel rattle, which I can only put down to the high pressure ‘FSI’ direct injection fuel system. This is reflected in the quoted idle noise figure of 86dB (and 90dB for the manual version) – well above any of the other Golf models, which range from 75dB-83dB. However, at anything other than very low vehicle speeds, this is not really an issue.
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By GlobalDataAutomatic – Drive Mode
In the standard automatic Drive (D) mode, I found that the transmission is rather too eager to change up, with 5th and 6th being used far too soon. Under normal driving conditions it tries to maintain an engine speed of between 1000rpm and 2000rpm. In some extreme cases it is possible to be doing 20mph in 6th gear, which makes it very difficult to pull away without labouring the engine (cue engine shuddering noise). What happens in practice, when you accelerate, is that the control system tries to change back down to 3rd or 4th, which introduces an inevitable delay, just at a time when you least want it.
But maybe there is another angle to this. What the Drive mode is doing quite well is to control the madness that lurks beneath the bonnet. So perhaps the D should actually stand for docile, for those times when you want to keep the beast under wraps. Suitable, maybe, for those occasions when Granny agrees to take the kids off your hands for a few hours. But hang on – who am I trying to kid? This is a Golf GTI, and nothing about it should be docile, or dull or drab – no excuses. The calibration for the Drive mode just isn’t right for this car.
Automatic – Sport Mode
In Sport (S) mode, as you might expect, the car is very keen to hold onto the lower gears, as the engine speed increases – even under moderate acceleration; perhaps a little too keenly in some situations, with 1st gear still engaged at 20mpg (cue sound of screaming engine noise), and a general attempt to maintain the engine speed between 3500rpm and 4500rpm. The exception, of course, being when you really put your foot down, when the strategy changes, and it upshifts only when you hit the 6500rpm red line. But when driving in busy town traffic it is difficult to get it beyond 2nd, whilst on the motorway I never managed to get it beyond 5th gear. A rough calculation of the likely speed at which 6th might kick in, based on the observed shift point, suggests that it would be used only at 130mph and above!
In both automatic modes it’s possible to override the car’s choice of gear, which is great if you feel the car needs a helping hand, but this does rather defeat the point of it being an automatic. Call me a cynic, but I can’t help wondering if the Drive mode has been optimised for the absolute best fuel consumption, and the Sport mode has been optimised for the best 0-60mph times.
Manual mode
In manual, once you’ve got used to the steering wheel mounted shift paddles (or push/pull feature on the gearstick), the operation is very easy. One downside for me, being used to a rather older and noisier Audi engine, is that it is sometimes difficult to audibly tell what the engine revs are doing. Although to be fair, this is a criticism that could be directed at any quiet, modern engine – I’ll just have to start looking at the rev counter instead. The other issue is to do with the small paddles being located on the wheel, rather than the steering column, which makes it difficult to find them when changing whilst cornering.
Even in manual mode, the car automatically selects 1st gear once the car has come to a stop. This is a nice touch, which is much appreciated at roundabouts and junctions, where I might only have been stationary for a moment. At the other end of the speed spectrum, the gearbox will change up if you hit the red line – great if you happen to be distracted by the exhilarating acceleration.
Overall my impressions of the Volkswagen DSG are good, but I would have preferred a control strategy which sits somewhere between Drive and Sport. I suppose what I was really after was an adaptive system, which allows me to teach it where I like to change gear, and for that to be replicated in the automatic mode. Having said this, the DSG has been extremely popular in the Audi, Volkswagen, SEAT and Skoda models in which it is offered. In the UK, 7% of all VW Golfs are sold with a DSG, while 8.5% of all Passats sold have the DSG option. Based on CSM estimates, the Volkswagen Kassel plant has produced between 460,000 and 500,000 DSG transmissions so far, since its launch in 2003.
Putting aside the slightly strange operating strategy, the transmission technology itself is very impressive. VW quotes shift times of 40ms but, to be honest, you don’t feel most them at all. What you do feel, and it would be impossible to change this even with a zero shift time (the UK company Zeroshift claims to be very close to this…..), is the change in engine speed. Every time the gear ratios change, the engine, by definition, has to re-adjust its speed, to match the vehicle speed at that instant. Of course, not all gear changes are achieved in 40ms, but even those that aren’t are done in a pleasantly smooth way, if a little slowly by comparison.
With Volkswagen having stolen a march on its competitors, the question now is who will be next? Well, according to CSM’s intelligence, it will be a race between Ford Europe and BMW, with announcements expected before the end of 2006: Getrag-Ford has been developing two DCTs called the MPS6 (or DCT450), for use with L4 and V6 engines, and a shorter SPS6 (or DCT470) for use with the longer L5 (Volvo) engines. Meanwhile, Getrag has been developing a DCT called the 436 (or 7DCI600), which is to be supplied exclusively to BMW. The first application will be the BMW M3, which is powered by a new 307kW/412hp ‘S65B40’ gasoline engine. Thereafter, expect to see it in various BMW 3-Series and 5-Series cars. Following them will be a Getrag 481 (or 7DCL650) unit for Ferrari, and the much delayed ZF unit in the Porsche 911.
But VW is certainly not resting on its laurels. We can soon expect to see a 200N.m version of the DQ250, called the DQ200, for use in smaller Volkswagen Group vehicles. And then there are the versions for cars where the engine is mounted longitudinally, like the Audi A4, A5, A6 and A8. These will get a 7-speed, 500N.m DCT called the DL501, which debuted recently in the Audi Roadjet Concept car, while some of the more exotic versions will get a DL700, rated at 700N.m. As can be seen from the graph, Volkswagen has very much grasped this new technology with both hands.
As more manufacturers enter the DCT market, we can expect to see further improvements in this interesting new technology, as experience is gained, and further research is carried out. And sooner or later, maybe by 2015, we can expect to see most of Europe’s vehicle OEMs offering Dual Clutch Transmissions to their customers.
Chris Guile is a Powertrain Analyst with the automotive forecasters, CSM Worldwide.
