The state-of-the-art full hybrid system, whose components are being co-developed by General Motors Corp., DaimlerChrysler and the BMW Group for production beginning next year, represents a major automotive industry milestone due to the unprecedented fully integrated combination of electric motors with a fixed-gear transmission.

As a result of its low- and high-speed electric continuously variable transmission (ECVT) modes, the system is commonly referred to as the 2-mode hybrid. However, the sophisticated fuel-saving system also incorporates four fixed gear ratios for high efficiency and power-handling capabilities in a broad variety of vehicle applications. During the two ECVT modes and four fixed gear operations, the hybrid system can use the electric motors for boosting and regenerative braking.

In summary, the four fixed gears overlay two ECVT modes for a total of six operating functions:

• Input-split ECVT mode, or continuously variable Mode 1, operates from vehicle launch through the second fixed gear ratio.

• Compound-split ECVT mode, or continuously variable Mode 2, operates after the second fixed gear ratio.

• First fixed-gear ratio with both electric motors available to boost the internal combustion engine or capture and store energy from regenerative braking, deceleration and coasting.

• Second fixed-gear ratio with one electric motor available for boost/braking,

• Third fixed-gear ratio with two electric motors available for boost/braking.

• Fourth fixed-gear ratio with one electric motor available for boost/braking.

The result is trend-setting hybrid technology that provides superior fuel economy, performance and load carrying capability.

The full hybrid system being co-developed by General Motors, DaimlerChrysler and the BMW Group has an overall mechanical content and size similar to a conventional automatic transmission, yet this full hybrid transmission can operate in infinitely variable gear ratios or one of the four fixed-gear ratios.

A sophisticated electronic control module constantly optimizes the entire hybrid powertrain system to select the most efficient operation point for the power level demanded by the driver.