An all out battle in the luxury car market has been launched by BMW, who have proclaimed that their new 7-series of large saloons replacements for the 2500 to 3.3Li series is in direct competition with Mercedes-Benz. The audacity of the Munich upstarts is furthered by prices in Britain, which are slightly more expensive than the equivalent Mercedes models. The three new models in the 7-series range, the 728, 730 and 733i, retail from £8,950, £10540 and £11,550 respectively.
The last two figures of each model number denote the cylinder capacity of these elegant, new cars. the 2.8-litre and 3.o litre cars have carburetter engines, while the 3.3-litre car has Bosch fuel-injection. A basic description suggests little more than rebodying of the old running gear: six-cylinder, in-line overhead camshaft engines; McPherson strut front suspension; semi-trailing arm rear suspension; four-speed gearboxes; ZF recirculating ball power steering. The truth is much more complicated and on paper at least the mechanical specification shows many sophisticated detail design advancements.
The new models are longer and wider than the preceding BMW long wheelbase saloons, the 3.3L and Li, obviating the need for, alternative wheelbases. They have more leg room, headroom, boot room and elbow room than the old long wheelbase cars. Not surprisingly they are heavier, too.
Their engines are uprated to cope with the extra weight. At the bottom of the range, the 2.5-litre engine has given way to the 2.8, which produces the same power, 170 h.h.p., as the old 2800, with slightly less torque. The carburetter 3,0 engine gains 4 b.h.p. for the same torque, while the top of the range model strives to keep up with the old 3.0Si performance standards by adopting the 3,210 c.c. fuel-injection engine, worth a couple of extra b.h.p, and a significant amount of extra torque. A 2.5-litre engine will be available to special order for certain export and diplomatic markets.
The two carburetter engines now use a single four-barrel Solex carburetter in place of two Zenith two-barrel carburetters, together with slightly modified combustion chambers. Better mixture control for performance, consumption and emission is promised. The 733i uses an improved version of the Bosch L Jetronic fuel-injection, together with electronic ignition. All models get a viscous cooling fan, assisted by an automatic electric fan in the case of the 733i.
Alas, there have been no changes to the ratios of the 4-speed Getrag box, although when we were at the Munich factory recently there was talk of a 5-speed gearbox being available in the not too distant future. Automatic transmission cars have benefited from the new ZF three-speed gearbox with a Eichtel and Sachs torque converter.
Although McPherson strut front suspension is retained, it features a novel development described as a double-joint spring strut, in which an additional ball joint is included. The thinking behind it is complex and not easy to follow; soffice to say here that the resultant geometry offers more variations than conventional geometry, allowing progressive anti-dive without taking extra space; keeping the big ventilated disc brakes in the air flow, improving steering return and smoothness and providing more stable braking under, adverse conditions.
The rear end gets a new tubular subframe to carry the semi-trailing arm and spring strut independant suspension, together with improved rubber bushing.
Obtaining sufficient vacuum to operate a conventional brake servo has become something of a problem on modern engines. BMW have overcome this with a hydraulic booster, which shares a common engine-driven pump with the ZF power steering. This system ensures full power-assistance from rest, its accumulator stores sufficient energy for eleven 80% stops without the servo working (i.e. if the engine fails), and a 0.15 sec. response time improvement is claimed, sufficient to knock 17.5 ft. off the distance required to stop from 80 m.p.h. Larger diameter, ventilated front discs are fitted and the braking system is split diagonally.
The styling has much in common with the 633CSi, as does the splendidly ergonomic facia layout, which features the Coupe’s push-button test system. The 733i has central locking on all doors, boot and petrol filler cap. A new heating and ventilation system includes rear compartment ventilation and separately adjustable heating and ventilation on the 730 and 733i. The big seats are said to be tuned to suspension frequencies. An abundance of sensible details includes a first aid kit contained inside the rear seat armrest, a front apron below the bumper of “self-restoring” plastic, which regains its shape after minor impact and larger, more powerful, outer headlamps, Long range cruising is ensured by an 18.7 gallon fuel tank.
We have already had the opportunity to try the new models: in right hand drive form amidst magnificent scenery north of Toulouse; and left hand drive models on BMW’s cold and damp Munich test track.
The appearance, finish and appointments are superb, the interior design a vast improvement upon the suddenly and curiously old-fashioned 3.0 Si which carried us to and front Munich Airport. It is a quality of finish which BMW intend to be maintained, too: the bodywork carries a six-year guarantee, in line with Porsche.
Starting the engine provokes that familiar throaty roar and slight whistle and initially there is little to distinguish the old and new cars in behaviour. Round the test track the new car continued that annoying trait of spinning its inside rear wheel round tight corners; the retention of that semi-trailing arm layout with its considerable camber changes came as something of a surprise, but BMW engineers explained that they had tried several different systems, including McPherson strut, without appreciable benefits. A limited slip differential would have helped and will he optional. Nonetheless this big car proved very forgiving and stable in nasty conditions of rain and unseasonal snow.
The real virtues of the chassis improvements became more obvious on the road. The steering was immediately more reassuring than the old, its power assistance almost imperceptible, its accuracy excellent. Even more impressive was the improvement in braking, BMW brakes have always had a lack of progression and feel, coupled with abruptness at low speeds. They are now beautifully progressive, more powerful and no longer susceptible to fade.
All the cars available in France had covered low mileages and were obviously very tight, which may well have accounted for a disappointment in the performance especially from the 733i compared to the old 3.0Si. They remain very fast by anything except V12 Jaguar standards amongst saloon cars, however. The nicest model of the lot proved to be a 728 with very smooth ZF automatic transmission. It was almost as quick as a 733i manual we followed and which we later drove and handled much more pleasantly. The 733i is perhaps a shade over-tyred on 205 section rubber against the 728s 195 section (no 730s, which also have 205 section tyres, were available in France). The big tyres also created more thump and rumble and possibly accounted for the more fidgety ride of the 733i. The ride showed no noticeable improvement over that of its predecessors, remaining firm, at times almost harsh. Both BMW and Mercedes still have 4 long way to go to match Jaguar’s standard of ride and road noise suppression.
We wonder how BMW will cope with the anomaly of a higher price for the 633CSi than for these more sophisticated, more roomy and comfortable big saloons. The word is in Germany that the coupe is not selling as well as it might. This better value, new saloon isn’t likely to help it much. – C.R.