Competition For Toyota's Hybrids

If the crossword puzzle clue is "hybrid car," the answer is probably "Prius." Since Toyota brought that model to the United States six years ago, the company has basked in a green public- relations glow even though Honda Motor was first with a modern gas- electric car (the Insight) and Ford sold the first hybrid sport utility vehicle (the Escape).

But with a mix of creative engineering, clever promotion and fortunate timing, Toyota Motor has set the de facto standard for the entire class of eco-friendly vehicles. It has licensed its software to Ford Motor and is selling hybrid components to Nissan Motor.

Toyota has half a dozen hybrid models in showrooms or on the way twice as many as any other automaker ranging from the Prius to the Lexus LS600hL.

The domination of Toyota's Hybrid Synergy Drive, however, is coming under assault from some of the industry's top engineers. For more than a year, in nondescript buildings in Troy, Michigan, a German-American consortium of BMW, DaimlerChrysler and General Motors has been working quietly to develop a distinctly different type of hybrid powertrain.

On Friday, the consortium's top executives formally introduced that system, which they call a two-mode hybrid, at an industry conference in Vienna. Most important details of the project had previously been shielded by the group, called Global Hybrid Cooperation.

The two-mode system will be available in a wide range of cars, trucks and sport utility vehicles made by the three companies, starting with the 2008 Chevrolet Tahoe, which is to go on sale in the autumn of 2007. GM says that compared with conventional Tahoes, the hybrid version will achieve 25 percent better mileage in combined city and highway driving.

While the two-mode system takes a new approach to hybrid drive technology, there are some similarities. Like all hybrids, the two- mode combines the power of a gasoline engine with that of electric motors; it captures energy from braking that would otherwise be lost; and it shuts off the engine at a stop. As in most of today's hybrids, batteries alone can power the vehicle at low speeds.

But the new technology is different in some crucial respects. It has the potential to operate much more efficiently at highway speeds, with a greater boost from the electric motors. The components are lighter and more compact and can be readily adapted to different types of vehicles. It is particularly well suited to large trucks and sport utility vehicles, where it will have the greatest impact on overall fuel consumption.

Existing hybrid systems have a single mode of operation, using a single planetary gear set to split the engine's power routing it to drive the wheels or charge the battery for both city and highway driving.