BMW 6 Series (E24)

The new 6 Series coupé, using the model code E24, was introduced to the press in March 1976, suggesting production commenced in 1975.

Initially there were two models available: 630 CS and 633 CSI. Karmann constructed the 6 series coupé, as well as the earlier BMW coupés. There were a total of 1665 units of the 630 CS (plus 410 630 CSi, bound for the United States) and 2858 units of the 633 CSi (this number also includes right-hand drive cars) produced in the first year, amongst a total of 4,933 cars produced for the year.[27]

Production of E24 continued in 1977 at Karmann as a complete assembly until August, when only the steel body shell was made by Karmann and then shipped to BMW's plant in Dingolfing for assembly.[28]

Karmann-bodied cars are now rare and highly collectable,[29][30] particularly in original condition in early factory colours such as orange (028 Phönix), green (079 Mitgrün), and yellow (070 Golf) - the later very rare.

In July 1978, the more powerful 635CSi variant was introduced. The 635CSi featured a close-ratio 5-speed gearbox and a single piece black rear spoiler. The M90 engine was a single overhead cam version of the M1's M88 engine, its bigger bore and shorter stroke resulted in 160 kW (218 PS; 215 hp) and increased torque. The aerodynamic changes reduced uplift at high speeds by almost 15 percent over the other E24 models.[31]

In 1979 the carburetted 630CS was replaced with the 628CSi;[32] this car had a fuel-injected 2.8L engine taken from the E12 528i. An anti-lock braking system became available as an option.

In 1980, the fuel-injection systems changed from Bosch L-jetronic to Bosch Motronic.[33] The 635CSi central locking system could now be operated from the passenger door and trunk.

Post-facelift model

In 1982 (model year 1983 in the US), the E24 was updated with parts from E28 5 Series, resulting changes to exterior styling, engines, chassis, suspension, electronics and the interior. The struts in the new front suspension were double-linked ones, making the car less likely to dip under hard braking. The new rear axle was nearly identical to the trailing arm layout of the E28 528i, with a new pitman arm to control camber changes.[34] Meanwhile, the ventilated rear discs had proven a needless complication and were replaced with solid ones. The rust protection was improved considerably along with the facelift.[15]

The 635CSi engine was updated to the 3,430 cc (209 cu in) M30B34, which used a smaller bore and longer stroke than the previous 3,453 cc (211 cu in) M90 engine. The 635CSi became available with a wide-ratio 5-speed manual or a 4-speed automatic transmission.

E24s produced after June 1987 were fitted with ellipsoid headlamps, as per the recently introduced E32 7 Series.[35] The front and rear bumpers and spoilers were redesigned to use a single design worldwide[36] (prior to this, models sold in North America used a different design from the rest of the world).

The 635CSi engine was updated to the higher compression M30B35,[37] which resulted in a power increase of 19 kW (25 hp) for engines with catalytic converters.

The 6 series was released in the US as the 630CSi in March 1977, with the 633CSi replacing it during the 1978 model year.[18] The US market version received larger bumpers and side marker lights, as required by federal legislation. The 630CSi is powered by a fuel-injected version of the 630CS engine. This 3.0 litre engine produces 176 hp (131 kW) and 185 lb⋅ft (251 N⋅m).

The 633CSi arrived in USA in September 1977 (for the 1978 model year),[38] replacing the original 630.[39] In United States/Japan specification, the 633CSi was powered by a 135 kW (181 hp) version of the M30B32 engine. Output later dropped to 130 kW (174 hp).

In September 1980 (1981 model year), the manual transmission for US cars was upgraded from a 4-speed to a 5-speed. A 3-speed automatic transmission was optional.[40]

In September 1982, North American and Japanese market models received a major facelift, as per the models sold in the rest of the world.

635CSi (U.S. version)

In November 1984, for the 1985 model year, the 633CSi was replaced by the 635CSi for the North American Market.[41] This model uses the M30B34 engine, which produces 182 hp (136 kW) and 214 lb⋅ft (290 N⋅m) at 4,000 rpm. An L6 "luxury edition" version of the 635CSi was available in North America for the 1987 model year. The L6 featured leather headliner and trim and an automatic gearbox.[42]

In 1988 the engine was upgraded to the M30B35. This engine has a capacity of 3.4 Litres (despite the model code and the "3.5" inscribed on the intake manifold) and produces 155 kW (208 hp) and 305 N⋅m (225 lbf⋅ft) torque. This upgraded engine resulted in catalytic converter equipped United States models offering similar performance to European models.[41] Self-leveling rear suspension was added to the 635CSi and M6 features list.[41]

M6 (U.S. version)

In 1987, North America and Japan received their equivalent of the M635CSi, called simply the M6. The main difference between the M6 and its European counterpart, is that the S38 engine is used instead of the M88. Compared with the M88, the S38 has a catalytic converter, the compression ratio reduced to 9.8:1, a double row timing chain, a shorter camshaft duration and a simplified exhaust manifold. The power output for the North American E24 M6 is 256 hp (191 kW), which is 22 kW (30 hp) less than the European M635CSi.[26]

Standard equipment on the United States market M6 cars included many features which were optional on the European cars, including heated power seats, self-leveling rear suspension, beverage chiller (cooled by an air-conditioning system) between the rear seats, air-conditioning vents for rear seat occupants, sunshade for rear occupants and an 8-speaker premium sound system.[43]