Giant road test 1979 BMW 635 CSi E24

2015 / 2016 Drive-My

Bavarian elegance E24 BMW 635 CSi. Latest version of BMW 630 Coupe E24 range, announced with 3 ½ -litre version of six-cylinder engine July 1978, with manual only gearbox. Original E24 630 and 633 replaced 3.0 CSi coupe at Geneva 1976; 633 CSi only available in Britain with automatic transmission since 635 launch.


Since, in spite of unnecessary overall speed limits in all European countries but enlightened West Germany, building fast cars is not yet illegal, it is encouraging to drive machines like BMW’s 635 CSi E24. It is sad that, to some extent, legislation has driven manufacturers towards heavier, fatter cars — which need bigger engines to provide the same performance — a retrogression which began in BMW’s case with the 633 CSi. But the 635 is nevertheless a highly satisfying return towards the standards set by the much loved 3.0 CSi, even if its greater frontal area and weight mean that it has lost an appreciable amount of the usual BMW economy.

The 633 CSi, which continues alongside the 635 CSi, is 6 per cent heavier and has roughly 10 per cent more frontal area than the previous 3.0 CSi. Compared with the 633, the 635 weighs 1 cwt (5.1 per cent) more but has the apparent advantage of a fairly marked air dam front and a lipped tail, said to cut lift by 50 and 15 per cent front-rear.

The engine is more different from the smaller-engined car than is immediately obvious. Where the ’33 has a capacity of 3,210c.c. produced with 89x86mm bore and stroke, the ’35 has 3,453 c.c. and 93.4x84mm — it uses the big bore siamesed block design developed from the Group 5 racing 24-valve. In spite of the bigger bore and shorter stroke, the small increase in capacity might be expected to have slightly the opposite effect, the engine’s performance peaks are both lower, thanks to different valve timing. Maximum power is 218 bhp at 5,200 rpm (633 has 200 at 5,500rpm) and maximum torque is 224 lb. ft. at 4.000 rpm (210 at 4,250).

The four-speed gearbox of the ’33 is replaced by a five-speed Getrag one, geared a little low as on most BMWs, at 23.55 mph per 1,000 rpm — a curious state of affairs here, when with such a wide spread of power it would have been so easy to have made fourth the true maximum speed gear, and fifth an economy overdrive, with small adjustments to the ratios. There is a 15 per cent bigger bore exhaust system, suitably altered Bosch L-Jetronic electronic fuel injection and a slightly higher (9.3-to-1) compression ratio, the car running on 98 octane as before. Tyre sizes are unaltered (Michelin 195/70VR-Min. XDX on the test car) but the rim width on the standard BBS aluminium-alloy wheels is increased by ½-in.

BMW 635CSi E24 interior

Above: Reflections seen here are caused by bounce-flash lighting and are not normally seen by driver. Instruments, from left, are fuel and temperature gauges, speedometer with six-figure mileometer and press-zero trip, and revcounter. Warning lamps in centre are for (from left) low fuel and high temperature, battery, indicators, oil pressure, rear fog lamps and, on right, high beam, fog lamp, handbrake and a spare. The six blank spaces across the top of the display are used on automatic 633 CSi as transmission indicators. Lamps are switched, pull-style, on left of column, fog lamps on right. Lamp check panel is on right. Heater controls comprise ambient air vents each side, temperature / air conditioning and distribution on left and right of quartz clock whose bezel is heater fan rheostat control. Below: Lamp check panel enables a quick look at all major services before driving away.


Performance

Smooth and zestful

Starting is typical of Bosch fuel injection cars. You are told not to apply any throttle from cold; turning the key for only a short period leaves the engine just turning over on its own, as if about to die — then, after a few seconds it picks up gradually to the right warm-up tickover speed, emitting that delightful and characteristic BMW high-pitched twitter from the exhaust. You get used to this behaviour after a while, since it is a reliable starter, but at first it is disquieting. Drive away is excellent, and you have to restrain yourself from maltreating a cold engine which is so willing to go.

1979 BMW 635 CSi E24 SPEED
MAXIMUM SPEEDS AT TEST 
Gear mph kph rpm
Top (mean) 140 225 5.950
(best) 141 227 5.950
4th 118 191 6.350
3rd 84 135 6.350
2nd 62 100 6.350
1 St 40 65 6.350

 

Not so once it’s warm. This is the epitome of BMW zestfulness — that glorious smooth eagerness of a BMW six which is such a hallmark of the breed. There is one BMW that, up to 100 mph is quicker — the BMW 323i E21 — but what the 635 CSi E24 loses to its big-engined little brother at the lower end, it more than makes up for in refinement and in the way it keeps going where the M20B23 2.3-litre falls off. The manufacturers claim the car to be fastest four-seat coupe made in Germany, with a top speed of 140 mph. The test car did exactly that in near still air, with the engine making a shade under 6,000 — 750 rpm (14 per cent) over its peak power. It is obvious that, if properly geared for maximum speed, the car would achieve perhaps 145 mph — of academic interest certainly, but if geared thus it would gain usefully in economy and unfussiness. For it is still fussier than some of its competitors especially the particularly quiet Jaguar XJ-S.


ACCELERATION FROM REST
True Time Speedo
mph (sec) mph
30 3.2 31
40 4.9 41
50 6.7 53
60 8.5 64
70 11.0 74
80 14.3 85
90 18.7 95
100 23.4 105
110 30.3 113
120 41.0 122

 

The advantage of undergearing which the German motor industry — and presumably the German driver — likes is of course easy top gear performance. The 635 has this in full measure, thanks to its generous spread of power. It will pull in top without protest from 19 mph — 800 rpm — and as the 20 mph increments show, it accelerates more or less evenly, give or take a half-second to 90 mph only gently falling off above that. This makes it a very relaxing car to drive generally.

STANDING START
Standing 1/4-mile: 16.2 sec, 85 mph
Standing km: 109 sec, 29.8 mph

 

Standing starts are best done using only around 3,300 rpm to produce mild wheelspin accompanied by some wheel-hop, any more wheelspin proved as usual to be slower. The Porsche-style gate pattern for the five-speed gearchange, with first on the dog-leg rather than fifth, makes the vital first-to-second change slower than usual. This is really a racing style arrangement, since first gear is only usually wanted once, on the start-line. For road use, the Alfa pattern with fifth on the dog-leg is better, since one rarely needs to change into top quickly whereas there are times when first is wanted fast.

1979 E24 BMW 635 CSi road-test

BMW M30B34 engine. Impressive engine compartment. Note tidy, well identified fuse box with its transparent lid.


ACCELERATION IN EACH GEAR
mph  Top 4th 3rd  2nd
10-30 8.6 5.0 3.6
20-40 9.1 7.1 4.7 3.1
30-50 8.9 6.4 4.3 2.8
40-60 8.7 6.4 4.1 3.5
50-70 8,0 6.7 4.3
60-80 9.6 6.7 5.4
70-90 10.0 7.1
80-100 10.9 8.6
90-110 13.1 12.3
100-120 18.0

 

Acceleration in any BMW is always exhilarating, and this one is no exception. There is a noticeable amount of attitude change — the car squats perceptibly on take off and after each gearchange. In spite of the awkwardness of first to second, there is a yelp of tyre squeal as the clutch bites again, and this is repeated on the faster change from second to third. Testing in December isn’t always blessed with the right weather, and the inordinately high cross wind in which we were forced to figure the 635 has had its effect on the results. Nevertheless, as the times suggest, the car is a delight to drive fast as well as slowly. The gearchange takes some learning, requiring deliberate but light movements; heavy-handedness is encouraged by the notchiness of the change, but is punished by a tendency to baulk which disappears if you are gentler.

There’s a rev-limiter at 6,350 rpm. In spite of the low peak power revs, we found it best to change up at 6,000 rpm. Response is superb, as usual on BMWs with the exception that on this particular car we encountered momentary bouts of total misfiring several times during hard acceleration — not we believe a typical fault.


Economy

What you’d expect

When comparing BMWs with competitors, economy has always been a strong point. But if engine size and weight and frontal area all go up, more energy is used to do the same job, and so it is not surprising to find the 635 CSi’s consumption getting closer to its faster rivals, and well below (at 17.5 mpg overall) its 3.3-litre brother’s 20.6 mpg. Nevertheless, there is still a worthwhile difference; among the comparison cars only the Lotus Elite, a smaller, lighter car, is better. To be fair, it should also be said that the 635’s overall test mileage is less than the 633’s so that the very thirsty MIRA test session distance occupies a larger proportion of the overall. The 15 ½-gallon tank fills easily except for the last half gallon which requires slow delivery because of blow-back from the breather system. The fuel warning lamp starts flashing at odd moments with at least two gallons left. BMW are, like Mercedes, delightful in detail; a pleasing one is the cup-like bracket in the fuel filler flap in which you can put the filler cap whilst re-fuelling.

FUEL CONSUMPTION
Overall mpg:  17.5 (16.3 litres/100km)  
Constant speed
MPH MPG
40 35.3
50 35.3
60 31.4
70 29.5
80 27.4
90 25.2
100 22.4
Manufacturers figures 25.9 

Drive-MY formula:

Hard 15.6 mpg

Driving Average 19.0 mpg
and conditons Gentle 22.5 mpg
Grade of fuel: Premium, 4-star (98 RM)
Fuel tank: 1 5.5 Imp galls (70 litres)
Mileage recorder: 1.6 per cent short
Official fuel consumption figures
(ECE laboratory test conditions;
(not necessarily related to Autocar figures)
Urban cycle: 14 8 mpg
Steady 56 mph 28.3 mpg
Steady 75 mph: 23.4 mpg
OIL CONSUMPTION
(SAE 20/50) 800 miles/pint

Road behaviour

Total obedience             

The car has that other hallmark of all BMWs — steering which at ordinary fast touring speeds is as near perfect a qombination of total obedience and weight as can be expected in a. road car. It is not matched by the car’s ultimate cornering, which is slightly let down by the usual BMW trailing arm readiness to break away quite abruptly if the driver decelerates in the bend — but there is less of this than before which is a pleasant change. Naturally, it is easy to provoke a tail slide with the power available, but the fairly high-geared steering — 3 ½-turns for a handily tight 34ft lock — makes correction relatively easy. The steering’s response is good. There is no serious amount of slop in the ball and nut steering gear, and the power assistance is strong enough to make parking easy but not so dominant that all feel is missing. Roll is limited to a comfortable and confidence-inspiring degree.

For all normal road use — and this includes fast, safe driving as opposed to track-style stuff — it is worth repeating that the response of the steering which is combined with the customary BMW readiness to turn in (to begin to turn) is something which makes the car particularly delightful to drive. On the other hand it is reassuringly stable, even in a cross wind at speed. We noticed, however, that at maximum speed the steering did feel a little lighter than before, suggesting that there is still some lift in spite of that modified front. Weight distribution is the same as that for the E24 BMW 633CSi at with 56.6 per cent on the front with the car unladen.

M30B34 - engined 1979 E24 BMW 635 CSi road-test

The ride is a little abrupt at low speeds, rather more so than you might expect, but it improves to the usual BMW standard at speed. Road noise is there, slightly less than average, mostly made up of bump-thump, though there are enough vestiges of road roar to be noticeable. At 80 mph the volume of the excellent Philips stereo FM/AM radio must be turned up, but not to an uncomfortable level. Engine noise is there — a pleasing sound, typical of all six-cylinder BMWs, a sort of deep moan when you accelerate, which is subtly exciting — making the car only just quiet enough if judged absolutely. Wind noise on the test car came from around the very prominent door mirrors and, appreciably more so, from the optional electric sliding roof.

SAFETY
BRAKING
Fade (from 85 mph in neutral)
Pedal load for 0.5g stops in lb
start/end start/end
25-50 6 55-35
25-23 7 50-35
30-25 8 50-30
40-30 9 45-30
50-30 10 45-30
Response (from 30 mph in neutral)
Distance
10 lb 0.18  167 ft
20 lb 0.30  100 ft
30 lb 0.55  55 ft
40 lb 0.75  40 ft
60 lb 0.95  31.7 ft
Handbrake 0.30  100 ft
Max gradient 1 in 3  
CLUTCH Pedal 40 lb. Travel 6 in.
WEIGHT
Kerb, 30.8 cwt/3,447 lb/ 1.564 kg
(Distribution F/R, 56.6/43.4) 
Test, 34.3 cwt/3,847 lb/1,745 kg
Max payload 794 lb/360 kg 

 

Brakes are just the right blend of power and low pedal effort. The ventilated discs resist fade convincingly and proved well up to the performance. The handbrake copes comfortably with the 1-in-3 test slope.


Behind the wheel

Clarity and simplicity

The driver’s seat cushion can be adjusted fore and aft, up and down, and for tilt, so that together with the seat back rake adjustment there is little reason for discomfort. Cloth or leather seating is optional without extra cost; we found the leather lacked some sideways location. The steering wheel has fore and aft, but not angular adjustment, which is a small pity because some of our drivers felt that the wheel itself was a little high for them. Pedals are nicely arranged, and heel and toe changes are not at all difficult. The instrument panel remains an example to other manufacturers in its carefully placed reflection-free glass, the tastefully simple yet explicit markings and the neatness and position of dials with respect to the steering wheel, which does not obstruct one’s view. We would continue to ask for an oil pressure gauge and an ammeter, in addition to the usual warning lamps in which the 6-series coupes abound. In addition to the main warning lamps in the instrument pod, there are as well a comprehensive panel of seven check lamps which on pressing a button tell you whether or not oil, coolant, washer and brake fluid levels, and brake lamps and linings are right.

The horn is controlled from thumb switches in the steering wheel spokes — rather too easily touched inadvertently and still not as ideal in an emergency as using the centre of the wheel. Electric windows are worked, rather slowly, with juddering, from switches on each side of the gearlever. The usual neat BMW heater fan rheostat is provided in the form of the bezel of the clock.

The heater itself continues to amaze us. How so many manufacturers, particularly makers of otherwise very good and expensive cars, can fail to take note of the simplicity, effectiveness and above all ideal temperature control of the air blending heaters used now for many years by Ford and Austin-Morris is beyond comprehension. That on the 635 is the depressingly usual water-valve controlled device one has learnt to expect from most Continental makers — it provides very poor temperature control, with little variation between full heat and none at all, plus slow response. Very tiresome on nearly £19,000’s worth of motor car, especially when this price includes the boast of air conditioning (an extra) neatly switched from the same heater temperature control. One good mark is for the side window demisting which is welcome in poor weather, and another goes to the ventilation which is adequate, at any rate in winter.

Extensions behind back seats on shelf cover useful concealed trays.

Visibility was a wonderfully strong feature of the elegant old 3.0 CSi body which had most pleasingly thin pillars on all corners and large amounts of glass. Presumably it was roll-over crush resistance and barrier impact test requirements which dictated the thicker pillaring of the replacement, but, although we would have thought that by using much thicker wall sections the windscreen pillars could have been kept to the same size as before, they are not too bad and the view is still good. You have got to remember that the size of those pillars is enough to hide a pedestrian momentarily however, and look more carefully. In the wet the proper British-biased screen wipers are appreciated by the driver, though there is a lot of area unswept on the passenger’s side. Also in the wet, incidentally, after standing overnight in rain, there was a small leak from the front left hand corner of the sunshine roof on the test car.


Living with the 635CSi

Overall one can sum up by saying that each of the Road Test team would very much like to. In addition to the overall pleasure of driving and running the 635, its detail design gives much satisfaction. True central locking is provided; turn the key or push down the sill pip (virtually thief proof as it has no shoulder under which a wire could engage) in the driver’s door, and both doors and the boot locked. Switches are all robust in feel and in the way they work. The bonnet is released by pulling an easily found lever under the dash on the passenger side — .it is on the driver’s side on left-hand-drive models and it is a pity that it isn’t changed over for this country; but it works well, unlike those on some other cars.

Room in the back depends on how much the front occupants sacrifice their legroom, as you would expect in a coupe. The backs of the rear seats are continued neatly over the shelf behind in the form of lidded shallow compartments for oddments. Other oddment space is fairly good; the lockable swinging-bucket type of glove compartment is big enough to carry a useful amount of guide books, maps and so on. The disadvantage of this type is that it becomes heavy to shut when full. At its side there is a handy rechargeable torch, permanently plugged into the car’s electrical system but fitted with an automatic cut-off arrangement to avoid over-charging. There are small spring-loaded pockets in the doors. Door mirrors on the test car are the remote electric sort, controllable fortunately from the driver’s side, since their ingenuity fascinates anyone unfamiliar with them. The driver’s one is standard as far as British market cars are concerned, but not the passenger-side one.

The electrically motored sunshine roof moves slowly, and makes a tolerable increase in wind noise at speed when open. It can also be moved to hinge up at the back, for extra ventilation without being wide open. Boot space is generous, although the single skin sides must be respected with any large sharp-cornered load that can roll about if not restrained. The usual superb BMW toolkit is provided, neatly stowed out of the way under the bootlid. The aerodynamic rear lip is made of soft rubbery material to prevent damage.

If not quite in the Jaguar class, the underbonnet layout is good to look at. All major reservoirs are easily found; the alternator is rather buried, but the battery, excellent transparent-lidded fuse box and distributor are all readily accessible.


The BMW E24 633/635 range

As far as Britain is concerned there are just two big BMW coupes (the carburettor 630 CS is not available here). The 635 CSi is the flagship of the BMW range at £16,499 (without those expensive extras) and is only available with manual transmission. Since the 635 introduction the 633 CSi is now the automatic version of the range, at £15,379; you can no longer buy a manual 633.


HOW THE BMW 635 CSi E24 COMPARES

Clearly, on all counts but economy the Jaguar XJ-S is dominant. Its larger engine naturally puts it on top as it should, and its combination of sheer performance and flexibility and refinement is completely unrivalled anywhere in the world. It is also still relatively good value for money.

Happily there are no duds in this field. The Lotus will appeal to the purist who values efficiency, an old Chapman strongpoint, though it is the least refined of the bunch.

The two most expensive cars vie closely with each other for second best performance; the BMW follows the Maserati and the Porsche, and is really closer to the Lotus than its dog-leg-first-gear limited 0-60 time would suggest. The Mercedes, because of its lack of a manual box option, falls behind on acceleration and economy.


ON THE ROAD

Top for roadholding must come, in strictly alphabetical order since it is very hard to say which is absolute topmost, the Jaguar, Lotus, and Porsche, with the Mercedes close behind. These cars all have relatively well-behaved rear suspension. The BMW 635CSi E24 is much better than previous semi-trailing arm cars from Munich. The Maserati’s rear end goes relatively easily too.

All steer well for all ordinary purposes, the Jaguar lacking some feel but having the best gearing for its size, needing only three turns for a 36ft lock. It rides very well and exceptionally quietly, and its brakes are well balanced. In power assisted form, the Elite’s steering also lacks enough feel, and would be better with slightly higher gearing and more willing self-centring; ride is good.

The Maserati’s steering, superb in its liveliness, feel and accuracy, is spoilt only by a clumsy 39ft lock; the ride is acceptable if rather firm. Feel, without road shock, characterises the Mercedes direction, plus accuracy. The 928’s steering is geared nearly as high as the Jaguar’s, has a little feel, is accurate except under braking when it wanders slightly but is otherwise superbly stable. The BMW could do with more feel, but does everything else in this respect just as well as the rest.

All of these are practical touring cars as well as high performance sporting machines, the four larger cars especially so; they in particular have the boot space of a conventional four-door saloon, but of course lack something in back seat space. The Lotus and the Porsche 928, both slightly smaller cars, are a little limited in luggage room, but their designs sensibly come to terms with the problems of rear seating in relatively cramped space by shaping the seats to encourage a knees-up posture.

The Maserati suffers mildly from the usual Italian car proportions of seating in front — pedals a little close, wheel a little remote — which is awkward for the longer-legged Anglo-Saxon. The Porsche and the Lotus are both cars in which one seems at first almost to sink; you are distinctly surrounded by car in the driving seat. This applies less so to the Jaguar and least of all to the two big German cars; the Mercedes-Benz 450SLC C107 and its Bavarian rival are cars in which you sit commandingly. Overall, the BMW appeals greatly in size and space, yielding nothing to the others here.


VERDICT

Undeniably, for best value for in all respects except economy and perhaps looks — and that is of course very much a matter of opinion — the Jaguar XJ-S is unapproached. Its trump card is of course its quietness and refinement; the near-silent sport cars at last The Lotus falls behind in refinement, which it is reasonable to assume is expected in this corner of the market It is likely that for solid quality the Mercedes has no peer, and its refinement is good. The Kyalami will appeal to the person who wants something subtly different; it is distinguished, and also very enjoyable The Porsche is also expensive, but an incredibly good all-rounder with no vices. The Jaguar aside, there is no clear favourite. The BMW will find favour with the man who ranks style as important as performance, and who prefers a vestige of sporting sound to total refinement, it is a worthy contender here, practical and very satisfying to drive.


MANUFACTURER: Bayerische Motoren Werke AG, Munich, West Germany

U.K. CONCESSIONAIRES: BMW Concessionaires GB Ltd, 991 Great West Road, Brentford, Middlesex TW8 9ED


Below: Big wide doors make entry and exit easy Cloth or leather (as here) are optional at no extra charge.

Right: Rear seating is minimal, but adequate for short journeys if front seats are set fully back.

Drop-down bucket-type glove compartment includes a re-chargeable torch plugged in when not in use, on right.

Boot is generous but its single skin sides must be borne in mind when carrying loose sharp-cornered items. Bulge under lid contains handsome and quite comprehensive tool kit.

Above: Side view is one of the better aspects of the 635, recalling much of the grace of the old 3.0 CSi and diminishing the thickness of the new car, evident from three-quarter front. Chief identifying features are the plastic stick-on stripes, and front and rear aerodynamic aids.

Below: Rear Up is soft-moulded for pedestrian safety; exhaust pipes are bigger for the larger engine compared with the 633 — up from 165in. to 2in. dia.

 DETAIL TECH DATA
Car 1979 BMW 635 CSi E24
Made in Germany
Car type Front, rear drive
ENGINE 
Type BMW M30B34
Head/block All alloy head / cast iron block
Cylinders 6, in line
Main bearings 7
Cooling Water
Fan Viscous
Bore, mm (in.) 93.4 (3.68)
Stroke, mm (in.) 84 (3.31)
Capacity, cc (in.)  3.453 (210.7)
Valve gear OHC
Camshaft drive Chain
Compression ratio 9.3-to-1
Ignition Electronic breakerless
Fuel injection Bosch L-Jetronic
Max power 218 bhp (DIN) at 5.200 rpm
Max torque 224lb ft at 4.000 rpm
TRANSMISSION
Type  Getrag 5-speed
Clutch  Hydraulic, diaphragm spring
Gear Ratio mph/1000rpm
Top 1.0 23.55
4th 1.263 18.65
3rd 1.776 13.26
2nd 2.403 9.80
1st 3.717 6.34
Final drive gear Ratio Hypoid bevel 3.07-10-1
SUSPENSION
Front location MacPherson strut
springs oil
dampers Telescopic
anti-roll bar Yes
Rear location Independent, semi-trailing arm
springs Coil
dampers Telescopic
anti-roll bar Yes
STEERING
Type ZF ball and nut
Power assistance ZF hydraulic
Wheel diameter 14.7 in.
Turns lock to lock 3.5
BRAKES
Circuits Twin, split front/ front and rear
Front 11 in. dia. ventilated disc
Rear 10.7 in. dia. ventilated disc
Servo Vacuum
Handbrake Centre lever, rear drum within disc
WHEELS
Type Cast all alloy
Rim Width 6 1/2 in.
Tyres make Michelin
type XDX radial tubeless
size 195/70VR14in.
pressure F36. R36 psi
EQUIPMENT
Battery 12V 66 Ah
Alternator 65A
Headlamps 110/220W
Reversing lamp Standard
Hazard warning Standard
Electric fuses 19
Screen wipers Two-speed plus intermittent
Screen washer Electric
Interior heater Water valve
Air conditioning Extra
Interior trim Leather or cloth seats, pvc head-lining
Floor covering Carpet
Jack Screw pillar
Jacking points Two each side, under sills
Windscreen Laminated, tinted
Underbody Paint system.
protection bitumastic. pvc

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