概念汽车实用英语毛矛概念汽车实用英语U7章节.pptVIP

PPT研究院 POWERPOINT ACADEMY * * AUTOMOTIVE TRANSMISSION Attempts to improve the fuel efficiency of automatic transmissions include the use of torque converters which lock up beyond a certain speed or in the higher gear ratios, eliminating power loss, and overdrive gears which automatically actuate above certain speeds. * AUTOMOTIVE TRANSMISSION In older transmissions both technologies could sometimes become intrusive, when conditions are such that they repeatedly cut in and out as speed and such load factors as grade or wind vary slightly. Current computerized transmissions possess very complex programming to both maximize fuel efficiency and eliminate any intrusiveness. * AUTOMOTIVE TRANSMISSION For certain applications, the slippage inherent in automatic transmissions can be advantageous. For instance, in drag racing, the automatic transmission allows the car to be stopped with the engine at a high rpm (the stall speed) to allow for a very quick launch when the brakes are released. * AUTOMOTIVE TRANSMISSION In fact, a common modification is to increase the stall speed of the transmission. This is even more advantageous for turbocharged engines, where the turbocharger needs to be kept spinning at high rpm by a large flow of exhaust in order to keep the boost pressure up and eliminate the turbo lag that occurs when the engine is idling and the throttle is suddenly opened. * AUTOMOTIVE TRANSMISSION The creation of computer control also allowed for a sort of cross-breed transmission where the car handles manipulation of the clutch automatically, but the driver can still select the gear manually if desired. This is sometimes called a clutchless manual, dual-clutch, or automated manual transmission. * AUTOMOTIVE TRANSMISSION Many of these transmissions allow the driver to give full control to the computer. They are generally designed using manual transmission internals, and when used in passenger cars, have synchromesh operated helical constant mesh gear sets. * NOT