Fuel Efficiency Improved by 15% Over Conventional Engines

This hybrid system combines a V8 gasoline engine with an 8-speed automatic transmission, a motor that also functions as a generator during regenerative braking, and a 120V lithium-ion battery unit. Unlike the series-parallel system used in Toyota's Prius, it employs a parallel system, similar to that found in Honda's Insight. BMW claims this system will reduce fuel consumption by approximately 15% compared to conventional engines.

In a parallel system, the motor assists the engine during startup and acceleration. Given that BMW's "ActiveHybrid" utilizes a lithium-ion battery with a capacity of 800Wh, the current capacity of its cells is estimated to be around 6.5Ah.

Typically, the control unit, which includes the inverter, is installed in a higher position than the engine to facilitate heat dissipation. However, in the "ActiveHybrid," it has been placed low, beside the oil pan.

This placement, within a robust die-cast aluminum box bolted not only to the oil pan but also to the transmission, appears intended to enhance rigidity. It's also likely influenced by the engine's internal exhaust configuration, which tends to make the upper engine area prone to high temperatures.

Production of this "ActiveHybrid" is slated to commence sometime in 2009.