Most motor manufacturers indulge in cosmetic face lifts to revise models, a policy which often goes down like a lead balloon on second-hand markets. With the new “little-six” 320, BMW have reversed the trend, to put a completely new heart into an existing body. A straight-sixcylinder engine of 1,990 c.c., with a single overhead camshaft has replaced the faithful four-cylinder engine of identical capacity. Concurrently the Same six cylinder engine has been fitted to the revised 520 and the 320i has been replaced by the 323i, which has a fuel-injected. 2.3-litre version of the new small six. Thus BMW can boast a range made up almost entirely of six-cylinder cars; only the 316 and 518 retain the old fours. In the case of the 320, considered specifically here, I wonder whether that very lack of cosmetic changes might affect its sales among the one-upmanship brigade, for only the sharp-eyed observer will spot the additional grille badge, wider wheels and tyres and larger exhaust which differentiate the “six” from the “four”?
The idea of a small six-is nothing new to BMW of course, the 328 in particular recalling past successes on the theme. In contemporary BMW engineering terms this latest six is new, inheriting little other than basic single overhead camshaft cylinder head design from the large sixes or the almost superseded four. In 2-litre guise the engine has a bore and stroke of 80 x 66 mm (the stroke is increased to 76.8 mm for the 323i, which won’t reach Britain until the Spring). The cylinder block is cast-iron and the crossflow head alloy. Surprisingly, BMW have adopted a cast-iron crankshaft, running in seven main bearings, containing 12 integral counterweights to reduce bearing loads and carrying a damper on its nose. For the first time on a BMW, the central single overhead camshaft, supported upon seven bearings, is driven by a toothed belt and operates the valves via short rockers. The four-barrel, downdraught Solex 4A1 carburetter has an automatic choke. Familiarly, the engine is canted over, but to a 20 degree instead of the four’s 30 degree angle.
This engine transplant is not a “shoehorn” job – the 3-series was designed around it in the first place -and the unit fits in quite neatly, although the plugs are very difficult to extract, as I was to find out when trouble struck the first of two road test 320s. A smaller, though more efficient crossflow radiator and an electric cooling fan overcome the problem of extra length.
In the old engine, BMW had one of the smoothest four-cylinder units in the business, so why adopt the extra complications of extra cylinders? Increased smoothness was one aim, but higher on the list of priorities was the benefit of improved thermal efficiency occasioned by the higher compression ratios which can be used with a six’s smaller combustion chambers. This is beneficial to both exhaust emission and fuel consumption, both subjects which are headed for tighter controls in the future. In fact the new engine runs a 9.2:1 compression ratio compared to the four’s 8.1:1 and while the fuel consumption of both test cars agreed with BMW’s claims in that direction, the Munich company carefully omitted to remind us in print that whereas the old engine was content to digest two-star fuel, its young brother demands premium grade.
The little six boasts an increase of 13.4 b.h.p. over its predecessor and indeed its 122.4 b.h.p. at 6,000 r.p.m. compares favourably with the 125 b.h.p. at 5,800 r.p.m. of the old fuel-injected 320i. The 323i promises to be a real flyer, with 143 b.h.p. on tap. A less marked increase in torque is shown over the old 320: 118 lb. ft. at 4,000 r.p.m. against 116 at 3,800 r.p.m. Offset against this is an increase in weight of 188 lb., to 2,459 lb., of which so to 60 lb, is accounted for by the physically larger engine.
I am fortunate enough to have had considerable experience of the six-cylinder 320, firstly on the Press launch in the South of France, from where I returned one to England in an extended journey across France, and then, more briefly, with a second right-hand-drive car in Britain after the first example developed a faulty Solex.
At first, static acquaintance this new model seemed to have little to offer over and above the original 320, which I road tested very favourably in Motor Sport, January 1976 and the less happy 320i (Motor Sport February 1977) and I don’t intend to dwell much on the creature comforts, which are much as before. A new and most comfortable upholstery cloth now covers the entire seat faces of this four-seater, two door saloon, the interior door panels have been neatened and the dashboard switches and levers restyled and more clearly labelled. I will reiterate my comment from the earlier 320 road tests that the curved facia layout is one of the best in the business, the clarity of instrumentation, the convenience of switchgear a credit to its designer. The seats are hard and at first uncompromising, but those miles across France proved this German recipe to be highly satisfactory, especially when accompanied by a driving position which, if a touch “sit-up-and-beg”, is very relaxing. Commanding visibility is afforded through the deep, extensive glass area, rear seat and leg room is cramped, the boot is roomy and heating and ventilation first class, though opening rear quarterlights are not a standard fitment. The second car had the benefit of a slide and tilt steel sunshine roof. I must make mention of the excellent paint finish, a department in which BMW, Mercedes, VW and Porsche can teach the British and Italians so much. Why?
The familiar 3-series character changes with a turn of the key and the springing to life of the little six, the engine mountings and the body less disturbed by “start-up” than the four. The soft-whirrings which are emitted are less typically “straight-six” than the sporting bark of the new in-line Rover engines. First time starting from cold is usually guaranteed by first prodding the throttle to activate the automatic choke.
One immediately obvious benefit of the engine change is the new-found flexibility and “laziness” which makes 20 m.p.h top gear trickling in traffic an expected duty of the engine rather than a punishment. In fact this 320 will pull away from 10 m,p.h. in top. This is in spite of a reversion to the 3.64 final drive of the 2002 from the old 320’s lower 3.9:1.
BMW have stuck to a four-speed gearbox in face of the almost standardised five-speed boxes amongst the opposition; as always, a five-speed ZF gearbox is listed as an option, but this is rather more suited to competition use. I understand that a more appropriate five-speed gearbox is under development at BMW. The four-speed box’s ratios have not been altered for this six-cylinder application though the geartrain has been beefed up. Light and positive in use, the gearchange is a delight, but the antiquated whine in the lower gears becomes more annoying than ever when associated with the purr of this new “six”. A noisy differential in the second car added to the whining.
This new engine certainly packs adequate punch, capable of accelerating the 320 from rest to 60 m.p.h. in just under 10 sec. and to a maximum of 112 m.p.h., some 6 m.p.h. faster than the four-cylinder car. Yet the smoothness of its manners and less willingness to rev at the top end of the scale might be considered as less sporting than the characteristics of the “four”; its real attributes are smoothness and low-speed flexibility. Acceleration from modest speeds in the higher gears is not remarkable in fact it feels a bit of a sluggard if the gearbox is not brought in to play to build up the revs. Even then it takes its time in all except first gear to reach the 6,400 r.p.m. red line, equivalent to 32 m.p.h., 6o m.p.h. and 90 m.p.h. in the gears. Up to about 4,000 r.p.m. the unit’s quietness is admirable, but above that limit an element of relative fussiness sets in, a sort of whirring buzziness from the top end of the engine, rather than the calico-tearing crispness of other small sixes.
This same fussiness comes into play again at cruising speeds above 80 m.p.h. At 70 m.p.h. or thereabouts the engine is almost perfectly silent. The buzziness is not an intense sound, but is out of keeping and not at all satisfying. It certainly does not prevent this small BMW being a very satisfactory high speed cruiser, capable of sustaining three figure speeds easily, albeit on a well-prodded throttle, as the first test car had been doing when the four barrel carburetter developed an incurable malfunction on the autoroute south of Orleans. The symptoms were of blocked jets, for the engine was happy on slow running or full throttle. I couldn’t cure it, so the only comfortable means of returning to England was to spend even more time at three figure speeds, punishment which this 320 rebuffed superbly! Back at BMW Brentford the malfunction proved to be more serious than errant muck and the Solex carburetter had to be changed.
Returning to noise levels for the moment, wind noise is too prominent at speed, particularly if the now “tiltable” facia fresh air vents are open. On the other hand, suspension and road noise is extremely well suppressed.
Whirring machinations apart I enjoyed this car and would need little persuasion to buy one if the editorial Alfa Spider was ready for changing. Ironically, it was not the well-publicised new engine which did the trick. With the new package have come suspension and braking revisions which have more than replaced the sporting characteristics the 3-series BMW has seemed to lack. The McPherson strut front and semi-trailing arm rear suspension has had its spring and dampers uprated, the old 5J x 13 in. wheels and 165 section tyres have given way to the 5 1/2 J wheels and 185/70 section tyres of the old 320i, ventilated front discs have been added (the 10.04 in. diameter is unchanged and the 9.84 in. diameter rear drums remain) and a direct-acting, 9 in. servo has replaced the 8 in. article. The handling is now a driver’s delight, the whole car much, much tauter in feel, the roll considerably reduced although still there and pitch and squat is much less marked. Power off it is an understeerer, power on it is is nicely neutral, very predictable and very safe, the last two descriptions being ones I could not attach to the 320i I tested last year. This small BMW is much more responsive to the sensibly high geared, smooth and positive steering. The extra stiffness has brought with it a choppier ride over rough surfaces, but I wouldn’t call the ride harsh and a less smooth ride must be a small price to pay for modifications which have put the fun back into BMW small car motoring.
Improved braking is an added bonus. The brakes of the old cars lacked progression and snatched, especially at town traffic speeds. Righthanddrive cars, with remote servos, suffered the worst. This insensitivity has given way to a progressive, firm pedal and the overall braking performance is enhanced further by better resistance to fade.
Power assistance is available on this new model, though the steering is really light enough. It might be of benefit to ladies using 320s regularly in town. Of the two test 320s, the first, on Continental tyres, had slightly lighter steering at parking speeds than the second, on Michelin XVS. The Michelins gave better roadholding at the expense of a lumpier ride and less positive steering.
I thought at first that the original 320 must be running on air, for the fuel gauge sttick solidly on full for 60 to 70 miles, a trait copied by the second car. In fact even that fast trip across France failed to bring the consumption below 23.5 m.p.g. and 25 m.p.g. was more normal. Most owners could probably expect a 27 to 28 m.p.g. average, with 30 m.p.g. perhaps in sight for the very light of foot. A one gallon larger tank, to 12.8 gallons, ensures a comfortable range of over 300 miles.
The 3-series has always presented a fine, compact, quality package, lacking a little in sporting appeal. The new six cylinder engine is not as sporting as might have been hoped, though it does give the car additional smoothness and refinement; the improved sporting desirability of this small six comes largely from the much improved chassis. Further development will no doubt make the engine more appealing and the 323i promises to be quite a motor car. Meanwhile the 320 presents excellent value for money amongst its competitors in the 2-litre up-market, at £4,999. —C.R.
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