7-Series and X6 Hybrids On The Way

[JoshCalkins]

BMW's Hybrid Models

BMW has been showing off their EfficientDynamics program in a number of new models, and the program has shown impressive results in taking traditional internal combustion engines and making them more fuel-efficient without sacrificing too much power. Perhaps the best examples of this program aren't found on North American shores, however. The 116d and 118d diesel 1-Series models (the latter of which won the "World Green Car Of The Year Award" in 2008) are known for their high mpg rates, their low carbon emissions, and their ample power. While it is unlikely that more BMW diesel models will be crossing the Atlantic, this continent will still get a crack at the EfficientDynamics models in the form of new 7-Series and X6 hybrids.

The 7-Series will have a traditional hybrid drivetrain, although it won't be as invasive as what is found on other hybrids like the Toyota Prius. The model will have a lithium-ion battery pack onboard that will aid the car in driving at lower speeds and at accelerating. The 7-Series hybrid will still have a decently-powered gasoline engine to maintain the model's powerful heritage.

BMW X6 Hybrid Concept

The X6 hybrid, however, will be another animal completely. The X6 hybrid will use a "Two-Mode" hybrid system that the company developed in cooperation with General Motors, Chrysler, and Mercedes-Benz. This system, as the name suggests, has two main drive modes. The first is called "Input-Split Mode," which is used in first and second gear. At a stop, the engine will automatically turn off in order to save fuel. Initial propulsion from the stop will come from two electric motors. If the battery pack has a low charge, the engine will turn on and be used as a generator to repower the battery. At higher speeds, third gear and above, the vehicle enters "Compound-Split Mode," where the gasoline engine is always on and is the main force used to propel the car. The engine's activity is strictly monitored by electronic fuel-efficiency devices.

Two-Mode Hybrid Drivetrain

One of the big things that sets this type of hybrid apart from more conventional types is that the aforementioned electric motors are actually housed inside the transmission and act as a Continuously Variable Transmission device. Whenever necessary, the extra torque from the electric motors can be applied to the wheels, helping with acceleration even when already driving at highway speeds. What makes this efficient is that a lot of fuel is used for speed increases, but less is used for maintaining a speed. So, if the extra torque from the two electric motors inside the transmission provides the boost to take you from 50 mph to 60 mph, you don't use any extra gasoline, thereby drastically improving highway mileage ratings.

No specific release date has been announced for the new hybrd models, but a recent release from BMW's head offices quotes Dr. Norbert Reithofer, the chairman of BMW's board of directors, as saying that both models would be in "production spec" by the end of the year. That makes it likely that these hybrid models could hit showrooms by this time next year.