A FEDERAL CASE

The 6-Series didn’t come to America until 1977. When it finally did appear, American buyers had the dubious pleasure of paying far more money for noticeably inferior performance. The initial federalized 630CSi model was heavier than its European counterparts, thanks to bigger bumpers that added nearly 5 inches (12 cm) to its overall length. The only engine choice at launch was a fuel-injected version of the 2,985 cc (182 cu. in.) engine making 176 horsepower SAE (131 kW). Despite its power-to-weight-ratio deficiencies, the U.S. 630CSi carried a starting price tag of about $23,500 (the equivalent of around $85,000 in 2010), nearly 50% more than a German-market 630CS. Admittedly, the 630CSi was around $4,000 cheaper than a Mercedes 450SLC, but neither was priced within the reach of mere mortals.

American critics liked the 630CSi’s looks and handling, but its towering price cooled their ardor. Most preferred the 5-Series sedan, which performed just as well, was far more practical, and cost a good deal less.

BMW, apparently stung by the criticism, hastened to introduce a federalized 633CSi in 1978, dropping the 2,985 cc (182 cu. in.) engine in favor of a smog-controlled version of the 3,210 cc (196 cu. in.) M30 six also used in the new 733i sedan. The U.S. 633CSi had only fractionally more power than the 630CSi — 177 hp SAE (132 kW) — but stronger mid-range torque gave it better real-world performance than the earlier car.

Still, many buyers had evidently reached the same conclusions as the magazine testers, and U.S. 6-Series sales were modest. BMW’s American sales grew impressively throughout the late seventies and early eighties, but the big coupes represented a very small fraction of that business. Throughout the E24’s lifespan, the U.S. market accounted for less than 30% of total sales.

THE 635CSi

The European BMW 633CSi was a close match for a 450SLC in overall performance, but in 1978, Mercedes upped the ante with the limited-production 450SLC 5.0 (subsequently renamed 500SLC), which featured a new all-aluminum 4,973 cc (305 cu. in.) V8 with 240 PS DIN (176 kW). Since the new coupe was both lighter and more powerful than the previous 450SLC, the 450SLC 5.0 was decisively quicker than both its predecessor and the 635.

Given Von Kuenheim’s Mercedes envy, such a challenge could not go unanswered. BMW’s response appeared in July 1978 as the 635CSi, powered by a new six-cylinder engine called the M90. Similar to the M88 engine developed for BMW’s short-lived M1 supercar, the M90 was bored and stroked to 3,453 cc (211 cu. in.), although it retained a SOHC head and two valves per cylinder. The combination was sufficient for an output of 218 PS DIN (160 kW), a healthy improvement over the 633CSi. Linked to a new Getrag five-speed gearbox, the M90 engine gave the big coupe’s performance a shot in the arm: 0-60 mph (0-97 km/h) was now possible in less than eight seconds while top speed climbed to nearly 140 mph (224 km/h), outstanding for the time. The following year, the 635CSi also got optional Bosch antilock brakes, again to maintain parity with Mercedes. (ABS was not available on U.S. 6ers until 1985.)

The 635CSi proved very popular, particularly in Germany, where it cost less than 10% more than the 633CSi. In its first year, the big-engine model accounted for nearly a quarter of production, rising to more than 50% in its second year. Starting in mid-1979, there was also a new base model, the fuel-injected 628CSi, replacing the carbureted 630CS. However, buyers who could afford a 6-Series were apparently unmoved by the smaller engine’s modest cost savings and slightly better fuel economy; BMW sold only 5,950 628CSi models between 1979 and 1987.

THE 6-SERIES IN COMPETITION

BMW racing teams were slow to adopt the E24, since the old 3.0 CSL remained competitive in European Touring Car (ETC) competition as late as 1979. Group 2 versions of the 6-Series made their first foray onto the racetrack in 1980. In 1981, Helmutt Kelleners and Umberto Grano used 360 hp (264 KW) racing versions of the 635CSi, prepared by Ruedi Eggenberger, to tie for the ETC driver’s championship.

In 1982, the Fédération Internationale de l’Automobile (FIA) switched the ETC from Group 2 to Group A rules, which greatly restricted the number of allowable modifications. BMW Motorsport and Ruedi Eggenberger decided to switch to the smaller 528i sedan, which Umberto Grano used to win the 1982 ETC driver’s cup. The following year, however, Eggenberger switched back to the 635CSi, which Dieter Quester used to win the 1983 driver’s cup. The 6-Series didn’t fare as well in 1984 and 1985, but Axel Feder won the 24 Hours Nürburgring both years, driving a Schnitzer-built 635CSi. Finally, in 1986, Robert Ravaglia drove another 635CSi to the type’s third and final ETC championship.

The 6-Series also fared well in Australian competition. Driver Jim Richards won both the 1985 Australian Touring Car Championship and the 1985 AMSCAR series in a 635CSi and became Australian Endurance Champion in both 1985 and 1986.

While the racing 6-Series never quite equaled the record of the 3.0 CSL, its competition pedigree was nonetheless impressive. It also cemented the 6-Series’ role as BMW’s image leader, a role it arguably fulfilled better than the company’s intended flagship, the decidedly Mercedes-like 7-Series sedan.