Volkswagen's new torque converter in the Polo and Vento explained
It's no surprise that the Polo GT TSI has been our favourite warm hatchback for a long time now. Earlier, it had a punchy 1.2-litre TSI engine and the sportiest of all automatic gearboxes — the acclaimed DSG. The new Polo GT TSI retains neither the engine nor the ’box, yet it still tops our list of enthusiast cars on a budget. Last month, we dug deep into the engineering behind the new 1.0 TSI EA211 engine, and now we’re focusing on the second bit of the drivetrain — the transmission. We’re talking about the six-speed torque converter from the Polo GT TSI that has replaced the DQ200 DSG unit, a transmission with a strong fan following in the outgoing GT TSI. This powertrain also resides under the hood of the new Vento, for enthusiasts looking for a bit more space.
Wait.. what is a torque converter?
Good question. I’m going to reuse the most widely used analogy to explain torque converters because, frankly, it’s a great analogy. Imagine two fans facing each other. When you switch on the first fan, the wind generated from it spins the second fan too. And if you hold the propellers of the second fan, it will stop turning despite the first one continuing to spin. The first fan in this analogy is the impeller, the second fan is the turbine, and the air is the liquid or transmission fluid. The impeller is connected to the engine, while the turbine is connected to the transmission. Accelerate and they move in harmony (thanks to the transmission fluid), but if you stop or select ‘P’ or ‘N’ on the gear selector, the turbine stops while the impeller continues (allowing the car to stop without stalling). Heard of something else doing a similar thing? Yes, a clutch. The ‘torque converter’ is actually a type of fluid coupling which replaces the clutch. This is of course a very simplistic explanation of how a torque converter works, in reality there are a hundred more parts and plenty of electronics but this is the basic principle.
Hmm.. so are torque converters any good?
Early torque converter gearboxes sapped a lot of power from the engine, affected fuel economy drastically and took about two and a half months to deliver a downshift. But when we drove the new Polo GT TSI we were stunned. The shifts were smooth and crisp, the gearbox was smart enough to upshift when needed and it was perhaps even better in slow-moving traffic. Also, thanks to the almost infinite slippage, torque converter ‘boxes have no jerks or hesitation. It also manages good fuel economy — 16.47kmpl (claimed) for the automatic, versus 18.24kmpl (claimed) for the manual. Moreover, torque converter automatics are also extremely reliable, primarily because there’s no clutch to burn and the fact that the large fluid reservoir keeps things relatively chilly. So the answer is yes. Modern torque converters are very good.
Okay but why move away from DSGs?
The answer to this comes in two parts. The first being that the new torque converters are put into entry-level cars to make them more price competitive. The torque converter is a tried, tested, proven and reliable technology that works well for mass volume cars. But Volkswagen hasn’t moved away from DSGs. Far from it! And that’s the second reason for the switch.
But what makes the DSG so good?
The Direktschaltgetriebe or direct shift gearbox is two partial gearboxes, each with its own clutch pack. One clutch pack engages the odd-numbered gears, while the other engages the even-numbered gears. This means that if you’re in first gear, with the odd clutch pack engaged, the even clutch pack has already pre-selected the second gear. But it is also smart, and uses throttle position, speed and brake position to intelligently pre-select a higher or lower gear. So when one clutch disengages, the other quickly engages the pre-selected gear, saving time, and achieving those seamless shifts with barely any break in torque.
Sounds cool, how did it come about?
The first signs of a semi-automatic transmission came from the factory teams at Le Mans, but they never really went beyond prototypes. Years later, Walter Rohrl sampled this gearbox in a Group B rally car and was impressed by its ability to give him all the power, all the time. Fast forward a few years to 2003, and that was when the first production DSG was offered as an option on the Golf R32. It was also the first largescale automatic that was more efficient than a manual. “Through the end of the last century, automatic transmissions were always regarded as sluggish gasguzzlers. The goal was to build a sporty and fuelefficient variant,” explained Hubert Gröhlich, director of Direct-Shift Gearbox Development at the time. Since then, the VW Group hasn’t looked back and has been developing it to become even faster and even more reliable than ever before. The DSG currently serves in more than 260,00,000 cars worldwide. And this will continue to grow when the Taigun gets the DSG.
As enthusiasts, we’ve always preferred the added dimension of involvement we get from a manual transmission. However, automatic transmissions have come a long way from when they used to be referred to as ‘slush boxes’. We have always hailed the DSG as the benchmark for automatic gearboxes, but the new torque converter on the Polo and Vento has opened our eyes. It delivers strong, enthusiastic acceleration; it doesn’t sap the engine of power; Sport mode lets you rev all the way to the redline and keeps the motor spinning in the meat of the torque curve, and the smart programming also delivers good efficiency. It really does fill in the DSG’s shoes very well. And it ensures the new Polo GT TSI remains our favourite warm hatchback.