Eight-speed automatic shift

Engineers from Ricardo and Weifang Shengrui in China are working together on the design of an eight-speed automatic transmission for front-wheel-drive cars.

Weifang Shengrui plans to manufacture the transmission and sell it in China from 2011.

The company has already acquired a development and production licence for the transmission concept, which was created by Peter Tenberge, director and chair of machine elements at Chemnitz University in Germany.

Lee Sykes, global product group director for Ricardo, said that the Weifang Shengrui eight-speed transmission will move the technology into the mid-priced automotive market.

'It will become the new state of the art for front-wheel-drive cars, not just in China but it will be a technology statement for the rest of the world to catch up to,' he said.

Sykes added that the design of Weifang Shengrui's transmission is conceptually similar to current eight-speed transmissions for rear-wheel-drive cars. The transmission will use a combination of epicyclic and parallel axis gearing. The design of the transmission includes three planetary gears used together with a single brake and four clutch units.

Sykes said that the extra shifts in an eight-speed automatic transmission make it much more difficult to design than a six-speed automatic transmission.

'As we get more and more gear ratios, the key challenge is to do a good job minimising the shifts or minimising the perception of those shifts in the eyes of the driver,' he said.

Sykes added that the drivers of vehicles using Weifang Shengrui's eight-speed transmission will notice improved acceleration because of the gearbox's lower gears, or greater span of ratio.

'They should also see some benefits in fuel economy because we can have more overdrive ratios at the top end as well,' he said.

Sykes estimated that cars with the transmission could see between five and six per cent better fuel efficiency over existing six-speed cars.

Siobhan Wagner