a homologation special built to make the car eligible for racing in the European Touring Car Championship. 1,265 were built. The "L" in the designation meant leicht (light), unlike in other BMW designations, where it meant lang (long). The lightness was achieved by using thinner steel to build the unit body, deleting the trim and soundproofing, using aluminium alloy doors, bonnet, and boot lid, and using Perspex side windows. The five hundred 3.0 CSLs exported to the United Kingdom were not quite as light as the others, as the importer had insisted on retaining the soundproofing, electric windows, and stock E9 bumpers on these cars. The CSL was not sold in the United States. Initially using the same engine as the 3.0 CS, the 3.0 CSL was given a very small increase in displacement to by increasing the engine bore by one quarter of a millimetre to . This was done in August 1972 to allow the CSL to be raced in the "over three litre" racing category, allowing for some increase in displacement in the racing cars. In 1973, the engine in the 3.0 CSL was given another, more substantial increase in displacement to by increasing the stroke to , rated at at 5600 rpm and at 4200 rpm of torque . This final version of the 3.0 CSL was homologated in July 1973 along with an aerodynamic package including a large air dam, short fins running along the front fenders, a spoiler above and behind the trailing edge of the roof, and a tall rear wing. The rear wings were not installed at the factory, but were left in the boot for installation after purchase. This was done because the wings were illegal for use on German roads. The full aero package earned the racing CSLs the nickname "Batmobile". The CSL competed in Group 2 form in the European Touring Car Championship, with CSL drivers winning the Drivers title six times in the years 1973 and 1975 to 1979. The CSL also competed in Group 5 Special Production guise, winning three rounds of the 1976 World Championship for Makes. In FIA Group 4 spec, notably when driven by Hans-Joachim Stuck (car featured in Enthusia Professional Racing), they competed against racing versions of the Porsche 911 and Ford Capri with some success. 2.5 CS The last version of the E9 to be introduced was the 2.5 CS in 1974.