LEXUS HYBRIDS IN 3D
Three dimensions of eco-luxury
This article is from our archives and has not been updated and integrated with our "new" site yet... Even so, it's still awesome - so keep reading!
Published on Mon, Jan 16, 2012
By: The LACar Editorial Staff
By Zoran Segina INTRODUCTION Car manufacturing history recognizes very few benchmark automobiles. All sport sedans, for example, are compared to a BMW 3-series. An F-150 by Ford holds similar distinction among full-size trucks. While the competitors may claim that their product is better than, faster than, or whatever than the benchmark, it is ultimately the brand identified after “than” that carries the coveted status. In the world of alternative automobile propulsion, the Toyota Prius falls into this benchmark category. Introduced in Japan in 1997, the car is now sold in more than 70 countries with cumulative sales of two million units. Only ten years from its worldwide debut, Prius’ sales in the United States reached one million. The widespread acceptance of hybrid propulsion has forced most major manufacturers, including such venerable brands as Mercedes and BMW, to augment their portfolios with hybrid-powered cars.
If most LA Car hybrid drivers fully grasped the complexity of the propulsion system under the hood, they might never dare take their daily commuters out of the driveway. In the most elementary form, a hybrid car shunts electrical power between the two motor-generators, running off the battery pack, to even out the load on the internal combustion engine. In the Toyota and Lexus engineered hybrids, an electromechanical system replaces a the geared transmission. Because an internal combustion engine delivers optimal power over a small range of RPMs and speeds, the driver needs a clutch or torque converter and transmission. The hybrid replaces this with two motor-generators controlled by a computer, a mechanical power splitter acting as a second differential, and a battery pack that serves as an energy reservoir. The battery pack feeds the motor-generator to propel the vehicle at startup, at low speeds, and under acceleration. When the right foot asks for more, or the batteries run out of juice, the gasoline engine gets a call. That is why the engine turns off for traffic stops. Then there are brakes. Whenever the car is rolling, or the driver presses the brake pedal, the motor-generator begins to converts kinetic energy into electricity which is then stored in the battery. The continuously variable transmission in the hybrid car cannot be rebuilt by Mona Lisa Vito of “My Cousin Vinny.” fame (the 1992 film starring Joe Pesci and Marisa Tomei). A computer program must split the power from the engine between the wheels, and electric motor-generator. No hybrid car can operate without the computer, power electronics, battery pack and motor-generators. In addition, a hybrid car is equipped with a sophisticated combination of planetary gear, electrical motor-generators and computer controlled electronic controls that adjust the amount of torque from the engine and motors as needed by the front wheels. What makes hybrid cars so efficient—especially in city driving—is the regenerative braking, turning the engine off for traffic stops, and stored electricity. That is why our test cars have lower EPA on the highway than in the city.
Fortunately for the typical LA Car driver, all of this technological marvel happens out of sight. In Lexus hybrids, the electromechanical interaction between the engine components should be even less noticeable. Generally, luxury car owners want their cars to be reliable, but not flashy. In Rolls Royces, for example, the tachometer is replaced with a gauge indicating reserve of power. A high-end customer need not be concerned with how fast the engine is turning. The LA Car staff recently had a chance to drive three Lexus hybrids. Take a look at what we found. To view "The First Dimension: CT 200h", click here