N
ew model was presented in July 1978, the great 635 CSi. It had a new 3.5 litre (3453cc) engine that was developed by BMW Motorsport. The engine block was developed from the M49 racing engine that had been so successful in the mid and late seventies, and also from the M88 four valve per cylinder engine that powered the M1 mid-engined sports car. With such genes it was natural that the new engine was coded M90.
Power ratings for the new 3.5 litre engine was 218 bhp at 5200 rpm and an amazing tourque of 191 lb.ft between 2000-5900 rpm, maximum 224 lb.ft where reached at 4000 rpm.
New 5-speed gearbox
Standard gearbox was a 5-speed Getrag 265/5.70 and with a final drive ratio of 3.07:1 the 635 managed to accelerate 0-62mph in 7.3 seconds, top speed was 140mph.
The suspension was modified with heavy duty roll bars, and so called “Anti-tilt blocks” (a.k.a. bump-stops) where mounted in the front strut springs.
External differences
Other news introduced with the 635 CSi was 6.5" x 14" BBS Mahle cast alloy rims with 195/70 VR rubber, new front spoiler and a plastic/rubber back spoiler that reduced the uplift about 15%. The back spoiler carried the BMW badge, as opposed to later models that had the badge mounted on the bootlid.
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The 1978 back spoiler was a more solid affair than later rear spoiler, and carried the BMW badge.
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For reference — rear spoiler from the 1981 model.
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New engine in the US model
The US market had been screaming for more power in the only model available over there, the 630 CSi. A temporary solution to that problem was a special version of the 3210cc engine that where used in the 5 and 7-series four door sedans. This engine included a 3-way catalyst with a Lambda sensor to control the exhaust emissions.
The new federal 633 CSi made a big difference even though it only had a minor horsepower increase, 177 SAE compared to 176 in the old 630 CSi, the major benefit was the improved torque, 196 lb.ft.
The US version of the 633 CSi had the same Mahle rims as the European 635 CSi, and a new rear bumper.
Comments & facts
Adrian: I've noticed that half the US 1978 630 CS's and 1978–1980 633 CSi's have metal (unpainted) between tailights – the others are painted black. From 1981 it's always black.
Production numbers for 1978
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Model
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Units
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630 CS
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610
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630 CS A
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314
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633 CSi
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1039
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633 CSi A
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610
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633 CSi RHDi
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82
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633 CSi A RHD
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423
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633 CSi USA
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467
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633 CSi A USA
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546
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633 CSi A Japan
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247
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635 CSi
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1193
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635 CSi RHD
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98
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Total:
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5629
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Source: Bmwcoupe.nu
