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Touring cars

transmissionIn 2011 the British Touring Car Championship (BTCC) introduced the Next Generation Touring Car (NGTC), which is based on a regulation package aimed at reducing costs in the series. Part of this package is the requirement that a 'spec' gearbox be run in all cars; previously, gearbox manufacturer choice had been free.


Mandating spec components is the route taken by many touring car championships, so here I want to look at some of the transmission types and technologies used in touring cars around the world.


If you look at different national 'touring car' series, it is clear that the definition of what constitutes a touring car varies somewhat. In the UK, they have always been closely related to their road-going counterparts - the same being true in the World Touring Car Championship - with both front- and rear-wheel-drive models competing. Both series use I4-configuration engines, producing about 300 bhp.


The German national series, the DTM (Deutsche Tourenwagen Masters), is a more serious proposition, using space-framed cars with power in the region of 500 bhp supplied to the rear wheels. Across the Atlantic, the Brazilian TC2000 also uses space-framed cars, which from 2012 will be powered by a 2.7 litre V8 delivering about 430 bhp to the rear wheels.


All of these series, excluding the WTCC, mandate the use of a 'spec' transmission - in the case of the DTM, teams can chose one of two boxes - so what sort of technology does an off-the-shelf, control transmission offer in 2012?


Starting with the BTCC, the gearbox specified under the NGTC regulations is a development of a unit with its roots from the turn of the century. The transmission is a six-speed sequential with two different casing styles to suit front- and rear-wheel-drive applications, both casings being made from aluminium.


transmission-BTCC-gearbox

An unusual feature of the new gearbox is that the gears on the layshaft are stacked in a non-conventional manner to accommodate an overlapping barrel gearshift system. In a conventional barrel shift mechanism, there is no overlap between the barrel, and the gears are stacked in numerical order - 1-2-3-4-5-6. In the new arrangement, the gears are ordered 1-6-2-4-3-5, allowing overlap on the barrel track and leading to a reduction in gearshift time with no difference in the way the driver operates the gearbox. Other interesting features include the inclusion of an external adjuster for the differential, allowing mechanics to rapidly change the diff characteristics trackside.


A very similar unit is also used for Brazil's TC2000 cars, which goes to show how versatile a modern racing transmission can be. Although the transmission needs to deal with a considerably higher power output, the maximum torque of the V8 in the TC2000 and the force-inducted I4s in the BTCC are very similar, which is the important factor in terms of transmission longevity.


Despite also using a V8, the German DTM cars are closer to sports prototypes than touring cars. They use a rear-mounted transaxle system, very similar to those found in many front-engined GT racers, and also feature a semi-automatic paddle shift system for actuation. DTM also operates at a much higher cost level than other touring car series, so there are fewer concessions to the bottom line. For example, where both the TC2000 and the BTCC use an aluminium alloy casing, DTM units are made from lighter but far more expensive magnesium.


As you can see, despite cost savings and spec parts, manufacturers are still developing new and innovative transmissions outside single-seater and sportscar racing.

Fig.1 - The current 'spec' gearbox of the BTCC. This rear-wheel-drive variant is also the transmission of choice for the Brazilian TC2000 championship

Written by Lawrence Butcher

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