BMW 6 Series (E24)

Model history

The E24 was a replacement for the CS and CSL coupés first produced in 1965. The CS 3.0 was almost changed by adding a few centimeters in height to make it easier for customers to get into the car. However, Bob Lutz rebelled against the decision and rough drafted an alternative version that soon became the 6 series.^[1] Production started in March 1976 with two models: the 630CS and 633CSi. Originally the bodies were manufactured by Karmann, but production was later taken in-house to BMW.

In July 1978 a more powerful variant, the 635CSi, was introduced (for the time being not available in North America and Japan) that featured as standard a special close-ratio 5-speed gearbox and a single piece black rear spoiler. The bigger bore and shorter stroke facilitated max 218 hp at 5200rpm and a better torque curve. For the first year, the 635CSi was offered in three colors (Polaris, Henna Red, Graphite), and could also be spotted by the front air dam that did not have attached fog lights. These simple cosmetic changes reportedly worked to reduce uplift on the car at high speeds by almost 15% over the non-spoiler body shape. This early model shared suspension components with the inaugural BMW 5-series, the E12.

In 1979 the carburetted 630CS was replaced with the 628CSi; this car had a fuel injected 2.8L engine taken from the BMW 528i.

In 1980 the 635CSi gained the central locking system that is also controlled from the trunk. Also, the E24 body style converted from L-jetronic injection to a Bosch Motronic DME.

In 1982 (Europe) and 1983 (US), the E24 changed slightly in appearance, with an improved interior and slightly modified exterior. At the same time, the 635CSi received a new engine, a slightly smaller-bored and longer-stroked 3430 cc six to replace the former 3453 cc engine and became available with a wide-ratio 5-speed manual or an automatic.

This slight change in 1982 (Europe) was in fact a major change as pre 1982 cars were based on the E12 5 Series chassis and later cars were based on the much improved E28 chassis. The only parts that remained the same were some of the exterior body panels. This fact can be verified by studying the parts lists.

E24s produced after June 1987 came with new, ellipsoid headlamps which projects beam more directly onto road surface (newly introduced E32 series also sporting them).^[2] The sleeker European bumpers were also discontinued. Previous cars had either a European-standard bumper or a larger, reinforced bumper to meet the US standard requiring bumpers to withstand impact at 5 mph (8 km/h) without damage to safety-related components. 1989 was the last year for the E24 with production stopping in April. The E24 was supplanted by the considerably heavier, more complex, and more exclusive E31.

M version

BMW M88 engine

BMW Motorsport introduced M 635 CSi in Europe at the Frankfurt Motor Show in 1983. It is essentially an E24 powered by the powerplant of the BMW M1 - the M88 (286 PS (210 kW; 282 hp)). Most of the cars were equipped with special metric 415 mm diameter wheels requiring Michelin TRX tires. A catalyzed, lower compression ratio version of the car with the S38 engine (260 PS (190 kW; 260 hp)) was introduced in the U.S. in 1987. All M6 cars came standard with a 25% rear limited slip differential. U.S. models included additional comforts that were usually optional on models sold in Europe such as Nappa leather power seats and a dedicated rear A/C unit with a center beverage chiller. Car and Driver tested a U.S. M6 in July 1987 and achieved a 0-60 time of 6.1 seconds, better than the BMW published 6.4 and 6.8 second times for the European and U.S. versions respectively. 4,088 M 635CSi cars were built between 1983 and 1988 with 1,767 U.S. M6 built.^[3]

Models timeline

Technical data

Manufacturer's figures except where stated ^[4] (does not include North American and Japanese models).

Models for North America and Japan

While in most markets several E24 versions were usually available, markets with strict emission control regulations received only a single model (except for the M6 that was later offered additionally). This meant that in North America and Japan, BMW offered the following models:^[5]

1980's US market 635 CSi, rear view

1988 US version BMW M6 with 5mph bumper

• 630CSi (MY 1977 through 1978½)
• 633CSi (MY 1978½ through 1984)
• 635CSi (MY 1985 through 1989)
• L6 (MY 1987 - Luxury Edition 635CSi NA-only)
• M6 (MY 1987 through 1989)

In 1977, the 6er was released in the US as the 630CSi. This was a fuel-injected version of the carburetted 630CS available elsewhere. Its 3-litre engine developed 176 horsepower (131 kW) and 185 lbf·ft (251 N·m) of torque.

In mid-model year 1978 the 630CSi was replaced by the 633CSi. US/Japan specification 633CSi cars had the M30 3.2-litre 181 hp (135 kW) engine until 1984. In 1985 the car was renamed 635CSi, displacement was increased to 3.4 litres and horsepower increased slightly to 182 hp (136 kW). The big difference, however, was torque. Whereas the 3.2-litre had 195 lbf·ft (264 N·m) at 4,000 rpm, the 3.4 litre powerplant managed 214 lbf·ft (290 N·m) at 4,000 rpm.

From model year 1983, North American and Japanese versions benefitted from the technical revisions and changes to the interior introduced elsewhere in spring or summer 1982. Its chassis was now based on the E28 and no longer on the E12. The front and rear suspension was also revised. Later a self-levelling rear suspension was added to the 635 CSi and M6 features list in 1988.^[5]

The US received its own M series E24 in 1987 called the M6. The S38 powerplant found in the US model had several modifications from the M88 powerplant in the European model, most notably: a double row timing chain, modified cam tray, different valve lengths, a slightly different cam profile, less elaborate exhaust manifold (rather than full headers), Bosch X5DC copper spark plugs (instead of Bosch Silver plugs on the M88) and the introduction of an oxygen sensor for the EFI. These changes coupled with the introduction of a catalytic converter for emission regulations reduced the output to 256 hp (191 kW). The US model also included a variety of options usually available on European models, to include: heated power seats, sport tuned self-levelling rear suspension, A/C cooled ice box between the rear seats, A/C vents for rear seat occupants, sunshade for rear occupants and an 8 speaker "premium" sound system.

In 1988, the US E24 was now available with the newest version of the M30, the 3.4L (first used in the E32 735i). Even though the intake manifold states 3.5 it's technically a 3.4 (3430cc) like the previous 3.4. This engine had an increased compression ratio, and updated Motronics/DME. The result was 208 hp (155 kW) and 225 lbf·ft (305 N·m) torque. In effect, this engine was identical to the catalyzed version newly available in Germany and other markets.^[5]

References

External links

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