Electrohydraulic manual transmission is a type of semi-automatic transmission system, which uses an automated clutch unlike conventional manual transmissions where the driver operates the clutch. The clutch is controlled by electronic computers and hydraulics. To change gears, the driver selects the desired gear with the transmission shift lever, and the system automatically operates the clutch and throttle to match revs and engage the clutch again. Also, many such transmissions operate in sequential mode where the driver can only upshift or downshift by one gear at a time.
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Depending on the implementation, some computer-controlled electrohydraulic manual transmissions will automatically shift gears at the right points (like an automatic transmission), while others require the driver to manually select the gear even when the engine is at the redline. Despite superficial similarity, clutchless manual transmission differ significantly in internal operation and driver's 'feel' from manumatics, the latter of which is an automatic transmission (automatics use a torque converter instead of clutch to manage the link between the engine and the transmission) with ability to signal shifts manually.
Use in road cars
In 1984, Isuzu introduced the "NAVi5", a semi-automatic gearbox with electronically controlled hydraulics, for their domestic-market Aska. Initially available with an automatic mode only, the later incarnations added a manual mode. It was operated with an H-pattern shift lever, not a sequential lever or paddles popular in today’s cars.
The most famous application of a sequential transmission on road-cars would be their use in some Ferraris since the late-nineties, beginning with the F355 F1. Their system, the most current version of which is called "F1-Superfast," with shift times of 60 ms is designed to serve as a link to their Formula One efforts. This technology has also trickled down to the cars of their sister company, Maserati where it is known as "Cambiocorsa". Alfa Romeo's Selespeed in 1999 was the first sequential transmission in a mainstream car, derived from the Ferrari system.
BMW offered a system simply called "sequential manual gearbox" (SMG) on the E36 M3(Starting in 1997), and later "SMG-II" on the E46 M3. The BMW SMG transmission has both automatic and manual shift modes. Inside the different modes there are different programmes, with six settings to control the upshift/downshift speed for manual operation, and five settings for automatic mode. BMW's final SMG gearbox, known as SMG III, was the fastest shifting gearbox at the time (2006), recording a 65 millisecond shift time in its most aggressive mode - a time only surpassed by Ferrari with the 599 GTO (60 milliseconds) and later the Lamborghini Aventador (55 milliseconds).
Later, the 3rd generation Toyota MR2 used Toyota's version, known as the "Sequential Manual Transmission" (SMT).
Finally, Volkswagen Group (parent owner of Lamborghini) introduced a sequential transmission to the Lamborghini Gallardo (E gear), and then adding it to the Audi R8 (R tronic).
BMW has since switched over to a Getrag dual clutch transmission in the latest M3, and Ferrari as well in 2009 with the California and 458 Italia.