Friday, August 10, 2007

First look on Porsche Cayenne Hybrid

Porsche Cayenne Hybrid

One of Porsche's primary aims has been the creation of a so-called "full" or "strong" hybrid (the terminology is evolving with the technology), with enough capacity to propel the car electrically with the gasoline engine turned off. The Porsche engineers have also sought to utilize as much of the original Cayenne as possible in order to preserve essential Porsche driving characteristics, reduce complexity and keep development costs down.

This layout is conceptually similar to that of the 2007 Honda Civic Hybrid, which also sandwiches its MG between the internal combustion engine (ICE) and the transmission. The drawback to Honda's approach is that the electric motor and engine are always connected. Even when fuel to the engine is cut during electric-only operation, the crankshaft and pistons continue to spin, creating friction and sapping power.

Porsche solves this by placing a computer-controlled "disengagement clutch" between the motor-generator and the V6 engine, allowing the ICE to be entirely disconnected and shut down during electric drive mode. When the engine is required to accelerate the car or recharge the battery, engagement shock is mitigated by careful control of the clutch and the automatic transmission's torque converter.

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