The BMW 3 Series is a compact executive car manufactured by the German automaker BMW since May 1975. Successor to the BMW New Class, it has been produced in six different generations and in five different body styles. It is BMW's best-selling model, accounting for around 30% of the BMW brand's annual total sales. BMW released its E21 in the wake of the 1973 oil crisis, nearly doubling BMW's worldwide auto sales figures in three years. The first generation was a two-door saloon model only. A factory authorised cabrio version was also built by Baur. The cockpit design of the E21 marked the introduction of a new design concept for BMW, with the center console angled towards the driver. This feature has become part of BMW's interior design philosophy for many years. As a sign of passive safety, all edges and control elements within the interior were rounded off and padded. Initially, all models used the BMW M10 four-cylinder engine. In 1977, the BMW M20 six-cylinder engine was added to the lineup. At the E21's release, three models were available: with 316 (1.6-litre), 318 (1.8-litre) and 320 (2.0-litre) versions of the BMW M10 four-cylinder engine. To draw clear visual distinction within the new model series, the 320 models came with dual headlights, while the 316 and 318 had single round headlights. At the end of 1975, the 320i was introduced; the engine was fitted with Bosch K Jetronic fuel injection, delivering 125 bhp (93 kW; 127 PS) on premium grade gasoline. In the mid-1970s, BMW had invested DM 110 million in a new engine series, designated as the M60, but later renamed as M20 upon the introduction of the E30 in late 1982.
At the 1977 International Auto Show in Frankfurt, BMW unveiled its new variants of the E21, featuring the new six-cylinder M20 engines. The four-cylinder 320 model was replaced with the 320/6, featuring a two-litre version of the M20 engine. The 323i model was introduced, featuring 2.3 litres and 143 bhp (107 kW; 145 PS), empowering this car with a top speed of approximately 190 km/h (118 mph). The braking system was also upgraded, with the 323i featuring disc brakes on all wheels.
In the meantime however, a performance gap had developed between the 98 bhp (73 kW; 99 PS) 318 and the new 320/6 delivering 122 bhp (91 kW; 124 PS). For the 1979/80 model year, the four-cylinder models were upgraded: the 1.8-litre power unit was revised and entered the market as a 90 bhp (67 kW; 91 PS) carburetor engine in the 316, while addition of Bosch K Jetronic fuel injection to the 1.8-litre engine raised the 318i to 105 bhp (78 kW; 106 PS) . Since there was now also room for a new entry-level model, the 315 powered by a 75 bhp (56 kW; 76 PS) 1.6-litre M10 engine made its appearance in 1981.
Alpina offered the B6 2.8. Introduced at the IAA in 1978, it was produced from March 1978 until January 1983. Only 533 units were built. The B6 2.8 transplanted the 2.8 L M30 engine from the 528i model into the 323i. Alpina fitted forged Mahle pistons, modified the combustion chambers, and used a Zenith-Pierburg-DL fuel injection system. These modifications raised engine output from 177 bhp (132 kW; 179 PS) to approximately 200 bhp (149 kW; 203 PS).