Sequential manual transmission
| Transmission types |
|---|
| Manual |
| Continuously variable |
| Bicycle gearing |
A sequential manual transmission (or sequential manual gearbox) is a type of manual transmission used on motorbikes and high-performance cars or auto racing, where gears are selected in order and random access to specific gears is not possible.
With traditional manual transmissions, the driver can move from any gear, to any gear, by moving the shifter to the appropriate position. A clutch pedal must be depressed before the new gear is selected, to disengage the running engine from the transmission. In auto racing, this process is slow and prone to human error; hence the development of the sequential transmission.
Overview
Sequential manual transmissions work by providing the driver the ability to select the gear directly before or after the gear currently engaged, usually by pulling a "paddle" (rocker switch) or (in cases where paddle shifts are banned) moving a lever. For example, if the transmission is in 2nd gear, pulling on the "up" paddle or lever would up-shift, selecting 3rd gear. Conversely, using the "down" paddle or lever would cause the transmission to downshift from 2nd gear into 1st.
Sequential gearboxes are also used in nearly all modern motorcycles as it is too cumbersome to have a manual shifter and would take up too much space in the confines of a motorcycle frame. Having control over the gear shifter with your left foot frees the rider's hands to operate both the clutch and brake without taking your hands off the handlebars.
Sequential manual transmissions are true manual transmissions, and should not be confused with automatic transmissions that provide some degree of user shifting input. One commercial example of this type of automatic transmission is the Tiptronic transmission. User shifting through buttons or lever does not necessarily mean that the transmission is a manual transmission.
Benefits
Beyond the ease of use from a driver's standpoint, an additional benefit of sequential manual gearboxes is that use of the clutch via foot pedal or hand control can be minimized or completely obviated, especially after coming to speed in first gear. Formula One cars of the 1980s and 90's made the most high-profile debut of this technology in motor sports, and enhanced variations on this theme are still in use in many forms of road racing and drag racing today.
Use in road cars
The most famous application of a sequential transmission on road-cars would be their use in Ferraris since the mid-nineties. Their system, the most current version of which is called "F1-Superfast," is designed to serve as a link to their Formula 1 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 was the first sequential transmission in a "normal" car. This transmission was derived from the Ferrari system. BMW also has a system simply called "SMG" (an abbreviation for sequential manual gearbox), but it is not a true sequential, as gears can be selected out of order. The 3rd generation Toyota MR2 uses Toyota's version, known as the Sequential Manual Transmission or SMT. Although it does not perform as well as the Ferrari Formula 1 based transmission, Toyota's SMT is the cheapest system, and the MR2 is the least expensive car to have a sequential gearbox. The Tesla Roadster also uses a sequential transmission.