In May 1975, the 3 Series succeeded the BMW 2002. It kept most of its characteristics, and added many evolutions, especially in terms of engines. At launch, it was the smallest model manufactured by BMW, which produced the 5 series, then the 6 and 7 series. It is also the best-selling BMW model in the world. The first 3 series appeared in 1975 to replace the 1502, 1602, 1802 and 2002 (E10/E20), of which it took over some engines. At launch, it was only available with a two-door body. It was also available as a convertible, bodied by Baur. It was designed by Paul Bracq who took up the general style of the 5 E12 series. As for the interior, it was particularly large for a car of this size. The first models were the 316, 318, 320 carburetor and 320i mechanical injection Bosh K-Jetronic, all equipped with four-cylinder engines of the M10 family. A new 1,990 cm3 six-cylinder engine was introduced in 1977 on the 320. This carburetor engine then develops 122 hp and replaces the old four-cylinder 320 and 320i. This 6-cylinder version is often referred to as the 320/6 in common usage in order to differentiate it from the 4-cylinder version (sometimes referred to as 320/4 by analogy). Then a second six-cylinder block (type M20B23) comes to top the range, a 2,316 cm3 with K-Jetronic injection of 143 hp on the 323i. A slight restyling was carried out in 1979 which, without losing its general line, made it more aggressive. Inside, the center console was modified, as well as the design and instrumentation. The most powerful models, 320i, 320/6 and 323i were identified at first glance thanks to their four-headlight grille with front monogram, although some 4-cylinder models were also equipped with them. The 323i also had a dual exhaust outlet, ventilated front disc and solid disc brakes at the rear. New interior trims appeared in 1980 to replace the old ones, the shape of the head restraints was also revised. In 1980, the 1,573 cm3 engine of the 316 was replaced by the 1,766 cm3 of the 318 but with a lower power of 90 chebaux, then the 318 was replaced by the 318i ("i" as injection, in this case Bosch's K-Jetronic injection). The 315 made its entry-level debut by taking over the 1,600 cm3 engine of the old 316. At the end of 1982, the new 3 series E30 replaced the E21, only the model 315 was produced until 1983. The E21 series was a huge success: more than 1,300,000 cars were built, all models combined.