Developed in a unique collaboration by the three car firms, the breakthrough unit, called E-drive, is the first to mate a fully-integrated combination of electric motors with a fixed-gear transmission.
The unit is smaller than a six-speed automatic gearbox, delivers higher efficiency, greater power-handling capabilities and leapfrogs the technology pioneered in the Toyota Prius and Honda Civic, engineers claim.
Traditional hybrids usually have just one electric continuously variable transmission (ECVT) mode. The new system uses two, a low speed mode and a high speed mode.
But the team of western engineers has gone even further. The two-mode system has been hooked up to a four-speed fixed ratio gearbox to give a total of six operating functions and a claimed 25% improvement in economy.
GM Hybrid powertrain engineering executive director Larry Nitz said: ‘It’s a best-of-both-worlds arrangement. We have the smooth acceleration of an electric variable transfer-type hybrid and the full-load abilities of a parallel hybrid.’
DaimlerChrysler hybrid development centre executive director Andreas Trukenbrodt said: ‘Even though the future role of E-drive is yet to be defined, there’s plenty of evidence to suggest motorists are seeking better economy in the face of higher fuel prices.’
And BMW AG hybrid vice-president Wolfgang Epple said: ‘What we have achieved is emissions reduction, performance and comfort. This is superior technology that will meet the requirements of all the brands as well as preserving the identity of each of our products.
‘It is our intention to set standards with a family of products that will increase our technical expertise… it’s very promising.’
During its two ECVT modes and four fixed gear operations, the system can use its electric motors for power-boosting and regenerative braking and paves the way for the car makers to package internal combustion engines with full hybrid transmission more cost-effectively to offer fuel-saving technology across a range of vehicles.
Because the system can be applied to front as well as rear wheel drive and imposes no significant limitations on engine size or type, it can be used with relatively minimal alteration.
GM will develop the system for its US-market trucks and luxury car ranges and could also offer it in its front-drive European brands.
DaimlerChrysler will introduce hybrid versions of its current Chrysler and Mercedes-Benz model ranges, but Epple said the introduction of BMW hybrids would coincide with the launch of new models.