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A Clutch to Outstrip the Rest?

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Dual clutch transmissions could account for up to 10 percent of global automotive demand by 2015, with inroads expected in North America and China. And lube manufacturers need to prepare for this coming shift in automotive technology.

At times the field can seem cluttered with automatic transmission types – each with its own fluid requirements. Besides DCTs, there are automated manuals, continuously variable transmissions, traditional three-, four- and five-speed step automatics, and demanding new trannies with six, seven and even eight speeds. Hybrid electric vehicles also have sophisticated designs, to seamlessly shift between powerplants.

Of all these, proponents say DCTs are the ones with the brightest prospects for the immediate future, because they combine fuel economy with smoothness and driving refinement to match the best automatic transmissions, while also providing the shifting response demanded by sporting drivers. Drivetrain component supplier BorgWarner expects the number of DCT units on the road to more than quintuple in the next five years.

Activity

Getrag Ford Transmissions, a joint venture formed in 2001 to develop and manufacture transmissions in Europe, is another of those riding the DCT wave. In series production since 2008, dual clutch transmissions for four different customers account for around 100,000 units on the 2009 order books, and for 2010 there are already 430,00 on order, Getrag noted in October. As DCTs pick up speed in Asia and North America, this boom will continue.

To keep step with these global markets, Getrag said it is ramping up production. With 24 locations worldwide – 17 of them production sites – it has adopted a cautious growth plan. For example, production of a second-generation DCT for the NAFTA market started up in Mexico in late 2009. In parallel, Getrags plant in Italy will switch over to production of the new DCT as well, the company said. By 2010, two new production sites will be built in China, where Getrag aims to double its turnover in the next two to three years.

Experts from Getrag, BorgWarner and lubricant additive supplier Lubrizol joined a mid-October webcast on DCTs, hosted by SAE and Automotive Engineering magazine. Ingo Steinberg, Getrags chief engineer of central engineering, told participants he expects DCT technology to be introduced into North America and to China as well. Chinas government clearly supports the introduction of dual clutch transmission technology as an enabler of CO2 emissions reduction, Steinberg explained. Regarding A and B class [smaller vehicles], the older force-feed torque-converter transmissions will be replaced by modern dual clutch transmission technology, leading to higher efficiency.

China, he noted, today has a manual transmission infrastructure, which lends itself perfectly for moving into the DCT arena. Additionally, Chinese OEMs and also Chinese end customers are very mindful of getting state-of-the-art technologies, and the DCT is the perfect match for that. Additionally, there is a lot of government regulation to push fuel efficiency up, and thats going to help DCT growth in China.

BorgWarner is similarly optimistic about China. It expects Chinas fledgling DCT market to grow to 1.2 million units by 2014 and 3.1 million units by 2020. In all, it expects about 13 percent ($234 million) of its total $1.8 billion in net new business from 2010 to 2012 will come from DCTs.

Efficiency

Getrags Steinberg noted how the technology combines the best from manual and automatic transmissions. The DCT technology provides much better fuel economy than corresponding vehicles with automatic torque-converter transmissions, he said. And Getrags second-generation DCT even beats out some manual transmissions, with reductions in fuel consumption of up to 20 percent.

Tsunlock Andy Yu, vice president of engineering at BorgWarner Drivetrain Systems, said their customer data over the last decade also illustrates the DCTs fuel efficiency benefits. Weve seen up to 15 percent fuel efficiency improvement depending on the baseline that is used, also depending on the cycle that is used to measure the fuel efficiencies, he said. That said, there has been a lot of advancement since the DCT was first introduced, and advancements are primarily in areas of reducing oil usage. Most automatic transmission engineers would tell you pump [efficiency] loss is one of the significant areas of focus when it comes to improving transmission driveline efficiencies.

To boost pump efficiency, BorgWarner is looking at a couple of enablers. One is use of high energy friction material that can reduce the lube usage, therefore allowing the pump size to decrease, Yu continued. Additionally, with low-leak solenoids, that also allows for resizing of the pump so that you could look for efficiency improvements in that way.

Liquidity

When should additive suppliers and lube manufacturers start to target DCTs? As early as possible, advised Dave Morl, global business manager for Lubrizols driveline additives group. As DCTs become more sophisticated, he explained, the trend will continue towards higher energy densities. And theres more stress on the DCT fluid in areas like anti-shudder performance, friction durability, efficiency and load carrying.

As a result, newer DCT fluids are specifically formulated for the transmission design, really with a focus on thermal durability, shear and oxidative stability, recompactability with the specific friction materials, and balancing this with base oil compatibility as well, Morl continued.

Generally, panelists agreed that synthetic fluids arent a must-have for DCTs. From our experience in terms of testing and developing additives and lubricants, it is not absolutely required that a synthetic base fluid is needed in development of DCT fluids, Morl said. Today I would say in most cases you could use a normally processed fluid and still be able to get the life performance, and also the low-temperature viscosity characteristic that works for the product, echoed BorgWarners Yu.

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