BMW's M-powered Coupe
— only for a few
WHEN motorsports enthusiasts think of BMW, images of the 3-litre CSL (ligntweight) road car and its turbocharged derivative handled by the likes of Ronnie Peterson, Hans Stuck and Gunnar Nilsson spring to mind. Interest waned a little when the 635 was introduced in 1978, extra weight and superior comfort being acceptable in the market place but robbing the Coupe of its sporting image. Now a version, the M635 CSi, brings back the sparkle to BMW's Coupe and allows a fortunate few to vie with Porsche's 928S on the unrestricted autobahnen. M-power is BMW's slogan today, fuelled by the success of the 3-series 4-cylinder block which is the heart of Nelson Piquet's Brabham Formula 1 car. The Motorsport division, headed by Dieter Stappaert and with designer Paul Rosche taking care of the technical developments, has already produced a high performing M535i and had all the equipment to hand to make a new flagship for the 6-series — a coupe style which has won the European Touring Car Championship more often than not over the past ten years, and a 24-valve engine straight from the M1 Coupe, a model of which only 450 examples were produced, and a good one today is worth upwards of £50,000. Looking back, you could say that the peak of the Coupe's development was in 1977 when the Motorsport division, then headed by Jochen Neerpasch, turbocharged the then 3.2-litre straight-six engine to produce between 750 and 800 horsepower, depending on boost. This machine's debut was at the Silverstone 6-Hours, and though the transmission was unequal to its task Peterson's handling of the monster was to make an indelible mark on our memory.
Neerpasch said then that it would take year to produce a transmission that would stand up to the job, but by the time that year had elapsed he was embarked on a new course, to produce the stunning M1 Coupe in collaboration with Lamborghini, Ital Design and Baur. Though the M1 never reached the production levels required for homologation (until the FIA relaxed its
DEVELOPED for the MI Coupe, the four salt six-cylinder engine now boasts even more power.
requirements) it resulted in the Grand Prix-supporting M1 Championship rounds, which we remember as much as anything for the glorious noise of the 277 bhp, four-valve power units.
That power unit is the inheritance received by the M635, improved in fact by the adoption of Bosch Motronic fuel injection and digital ignition system, a higher 10.6:1 compression, and an increase in power to 285 bhp. Coupled with this increase in power is a substantial improvement in the torque curve, which now peaks at 251 lb ft at 4,500 rpm.
Coupling this power unit to the rear wheels, via a 25% ZF limited slip differential, is a superb new 5-speed close ratio gearbox which has reverse gear out on a limb to the left, fifth on a limb to the right.
BBS split-rim alloy wheels carrying Michelin TRX tyres, 220/55 VR specification, take care of contact with the road, and the external appearance is completed with a deep chin spoiler and a discreet rubber spoiler across the bootlid.
By courtesy of BMW (GB) Ltd in Bracknell and the parent company in Munich we were able to spend a day with the M635 CSi in Germany in mid-January. Just seeing the car at the Frankfurt Show had made us determined to drive it as soon as possible, the car in our photographs being a pre-production model, series production starting about now for no more than 200-300 European customers. In 1985 production will be extended to 600-700, and this figure will include some right-hand drive models though the M635 will certainly remain very exclusive indeed.
The BMW Coupe has a classical shape, and a scarlet example still manages to look stunning on a bleak, otherwise cheerless day. We were advised to head south towards the Austrian border, on a lightly trafficked road to Garmish, so that 80 kilometres of autobahn could be covered as an initiation. The deep, expensive looking Recaro seats felt right straight away, and offered us a nice arm's length position behind the leather-covered steering wheel. There are just two main dials in the binnacle, a 280 kph speedometer and a rev-counter which has a thin red line starting at 6,500 rpm, thickening at 6,800 rpm where the rev-limiter operates.
We blessed BMW for continuing to exploit the normally aspirated potential of the engine, not the turbocharging route that they looked at in 1977 (and, indeed, as far back as 1969 when the 2002 Turbo won its class in the European Touring Car Championship). Turbocharging may be one expedient for extracting a lot of power from a comparatively small engine, but unless it's very well engineered it can leave the unit lacking in torque, and will certainly mute what could be an interesting engine/exhaust note. Not that we advocate noisy exhaust systems, but a well-tuned and suitably subdued note is, surely, part of the pleasure of owning a sporting car?
Our first impression of the M635 CSi was that of a machine that could do credit to itself on a race track in standard trim. The driving position, the road feel that comes through the seats and the steering wheel, the well-tuned engine noise and the close-ratio gearbox all give that sensation of driving a competition car, a thoroughbred. Do not deduce, though, that the Coupe loses its refinement. The build quality remains excellent, the Karmann body going down the Dingolfing assembly line in the usual way, and the nice sound does not imply raucousness. The suspension feels firm, more at low speed, but by no means uncomfortable. Though snow lay deep along the sides of the roads, the surface was well cleared and dry as we sped south, revelling in the BMW's performance. The engineers' performance chart confirmed our own impressions, first gear taking the car to 68 kph (42 mph), second to 110 kph (68 mph), third to 165 kph (102 mph), and fourth to 210 kph (130 mph). Other cars, seemingly reversing towards us at speed, made us slow down when the speedometer was hovering towards 240 kph (149 mph) in fifth, but the needle was still moving upwards at the time and there was no doubt at all that the Coupe would exceed 150 mph given time. The 635 was rock-steady at these speeds, and felt completely undramatic too. It's a nice feeling that one can drive like this legally in Germany, though there is no way that we would overtake even one car, let alone two in convoy, at such a speed. But to slow down to a relaxing, comfortable and acceptable 100 mph is now a revelation to us, making us reflect on our tedious 70 mph motorway limit. And though totally in love with the refined howl of the power unit, we imagine it would become tiring after a long period at sustained high speed, meaning much above 100 mph. On the other side of the coin, the M635 CSi is perfectly tractable right down to 40 kph, or 1,000 rpm, in fifth gear. We did plenty of that sort of motoring too, in the villages such as Oberammergau, home of the Passion play, and on icy roads which, though gritted, were not liked by the BMW on what the Germans scathingly call "summer tyres". "But of course it doesn't like snow," they said when we got back. "If we had known you were going into the mountains we would have fitted snow tyres." Well, even if we had known that winter tyres were on our options list we would have declined.
We were glad of the standard ABS braking system on the mountain roads, giving the BMW that extra dimension of safety. It is a peculiar experience to be able to brake hard on packed snow, and feel the pedal pulsating beneath your shoe. The car slows only gently, but in a straight line and under perfect control, this control remaining even if you turn the wheel. Despite the power system the steering is nicely weighted, heavier than on a normal 635 by virtue of the wider tyres and passing on more feel of the road. As for the handling, we can only pass the opinion that it felt well-balanced and secure, since our distance of 340 kilometres in a day was all on motorways or snow-covered by-ways. Comparisons will inevitably be made with Porsche's 928S 5-speed, since the two models have similar appeal and will be aiming for the same type of customer. Many customers, most perhaps, are totally loyal to one marque or the other and would not dream of switching, but still there will be many with an open mind in the market of a high-performance two-plus-two. The Porsche, which has aluminium doors and engine cover, has a better power-to-weight ratio (310 bhp 1,450 kg) than the BMW M635 CSi (285 bhp / 1,500 kg,, yet the performances are very comparable up to 100 mph, both reaching this mark in about 14.5 seconds. Beyond that the Porsche would edge ahead to a maximum speed of 164 mph, the BMW running out of puff at a claimed 158 mph. These maxima are, of course, purely academic even in Germany, but one can never deny the importance of having a higher top speed than the opposition! Ironically, bearing in mind Porsche's forte of building sports / GT cars and BMW's mission of building sporting saloons, the Munich product is the more sporting of the two. The BMW is noticeably more taut, the seating and driving position more sporting, the engine note more enticing and the gearbox having closer-matched ratios. In cost terms, the BMW is five per cent dearer in Germany, and a similar disparity in Britain would take the price to £32,250 in the UK next year at current values,
We understand that the M-power version of the 635 will not be homologated for competitions, since the 24-valve head could not be accepted as an evolution. That being so, a target of 5,000 identical cars being produced in 12 months is clearly out a question. So, this is a model which will remain exclusive, for discerning customers and the only question we cannot answer is why it took BMW so long to produce M635 CSi. — M.L.C.