Road test 1985 BMW 735i Automatic E23

1985 BMW 735i Automatic E23 – more efficient E23 7-Series BMWs introduced in December 1982 featuring latest 10-to-1 compression ratio, 92x86mm, 3,430cc M30 engine (first introduced in the latest 6-Series E24), with full Bosch Motronic digital ignition and L-Jetronic electronic fuel injection. New ZF 4HP22 four-speed automatic transmission has automatically engaging lock-up of the 31.1 mph per 1,000 rpm overdrive top gear. Modifications to front grille, pillaring and addition of bib spoiler reduce drag coefficient by nine per cent. Front anti-roll bar is stronger. Rear semi-trailing arms now run at 13 (instead of 20) deg to improve handling.

Until recently it has been assumed that one has had to accept a significant penalty in fuel consumption – and to a lesser extent performance – in cars fitted with automatic transmission if only because of the power wasting effects of a torque converter. One of the first applications of an automatically en gaging top gear lock-up was on the three-speed Chrysler Torque-flite transmission used by Aston Martin. The ZF 4HP22 transmission, seen for the first time at the 1982 NEC Show, fitted to the new E23 7-Series BMW, takes the theme a step further by using a clutch to lock out a very high overdrive fourth gear (giving some 31.1 mph per 1,000 rpm) at any speed above 55 mph, although on light throttle openings fourth will engage at as low as 35 mph – at engine idle speed.

Better fuel consumption is claimed for the new automatic than for the manual cars, but some of the much improved performance and efficiency of the E23 7-Series is undoubtedly due to other improvements. Aerodynamic drag is reduced by nine per cent (from an admittedly pretty high, independently tested, Cd of 0.45) thanks to a subtly altered grill, front air dam, new A-pillar fairings and mirrors (all of which help reduce wind noise), but perhaps more significant in the overall efficiency equation, is the incorporation of the less oversquare 92.0 x 86.0mm, 3,430 c.c. (instead of 93.4 x 84.0mm, 3,453cc) straight six first seen in the all 635 6-series coupes (1982 E24). This unit not only runs with a 10.0-to-1 (instead of 9.3) compression ratio but also with the fully computerised Bosch Motronic ignition/L-Jetronic fuel injection system. Quoted outputs are virtually unchanged with 218 bhp (DIN) available at 5,200 rpm, and 228lb ft torque at 4,000 rpm, but the torque curve is significantly fatter in the mid-range.

The rear suspension now uses the 13 degree (to the crosswise axis) semi-trailing arm angle (instead of 20 deg) in conjunction with increased anti-squat and the anti-toe change links first seen on the E28 5-Series. There is else a stiffer front anti-roll, bar.

Better door sealing is now incorporated and there is a new cloth roof lining to reduce noise levels. Such items as electric windows, mirrors, central locking, headlamp wash/wipe and rear seat belts are fitted as standard. The test car was also provided with the by now well-known on-board computer, an electric sunshine roof end electric seat adjustment, a limited slip differential cruise control, and a very expensive Blaupunkt Toronto SQR 32 stereo radio/cassette player and four-speaker system. With the high level of equipment in mind it is interesting to note that the test car tipped MIRA’s scales at 31.3cwt, which is an almost inconsequential 40lb more than its predecessor.

Aerodynamic improvements (opposite page) post 1982 E23 7-Series include rounder grille, revised bib spoiler (containing fog temps), new A-pillar fairings and door mirrors. Blade-type headlamp wipers are a standard fitment. Bumper have tough rubber-faced centre sections, and side body protection is provided by bump strips.

Performance

Not only fast…

But superbly responsive, flexible and impressively refined. Certainly BMW’s claims that the new 735i Automatic E23 has more performance and economy than previous manual cars is entirely justified. Exact comparisons are difficult because our previous BMW 735i E23 manual was tested in stronger wind, but the improvements are sufficiently marked to suggest that in similar conditions the new automatic would still be quicker than the old five-speed manual.

Slight surface dampness did not prevent the restyling E23 735i automatic getting away to an excellent start, the limited slip unit doing a good job in preventing any excessive wheelspin. With no apparent gains to be had by fully “stalling” the torque converter against the brakes during standing starts, we used a moderate amount of throttle prior to releasing the left foot and flooring the right. After a momentary slither from the rear tyros, the car got to 30 mph in 3.0 sec and 60 mph in a remarkable 7.8 sec (far quicker off the mark than any comparable car) then rushed on to 100 mph in 20.7 sec (2.2 sec faster than the old E23 735i 5-speed) and 120 mph in 37.7 sec, which the previously tested manual could not roach at all within the confines of MIRA’s one mile horizontal straights.

Full throttle up-change points are well chosen, with shifts occurring at 5,800 rpm and 5,700 rpm. We found that although we could not better the lower end of the acceleration range by making manual shifts, a marginal improvement in top end performance could be gained by revving the engine to 5,900 rpm (within 50 rpm of the test car’s rev limiter cutting in) in second gear before moving the T-handle selector forward a notch.

It should be explained that although the gearbox is a four-speed unit, it operates as a conventional three-speed under full throttle acceleration, fourth only engaging as pressure is released on the throttle. Thus on full throttle the gearbox remains in third right up to the car’s maximum speed; a mean of 130 mph previous pre 1982 E23 735i manual 129 mph) with the engine revving at 5,750 rpm, some 550 rpm beyond peak power. This apparent mismatch between the peak power point and top speed has always been a feature of BMWs, yet as in previous test cars this 735i engine displayed no unwillingness to send the needle towards the red sector of the rev counter. On the road the gearbox is notable for its responsive, yet smooth, part and full throttle up and downchanges (even when it has to change down two gears), yet where shifts between third and top are concerned this very responsiveness can lead to the rather irritating situation where for fairly small changes in throttle opening the gearbox “hunts” between fourth and third, say when driving briskly on a twisty B road. This situation is clearly preferable to a hefty prod being required to get a down-change, and can be easily avoided by selecting “3” and thus having the gearbox revert to a normally geared three-speed. Set the restyling E23 735i up with the cruise control in operation on a long incline and one can feel the throttle being gradually opened to maintain speed until a downchange occurs. This automatic speed hold device, worked by a column stalk, is exceptionally smooth in operation, unlike some which open and close the throttle quite jerkily. On light acceleration a 400 rpm drop can be felt as the torque converter is positively locked out, which gives some idea of the losses that would be occurring on wider throttle openings without the lock.

Perhaps more impressive than ever is the manner in which the BMW responds in the mid-range. Except at the very top end, the E23 7-Series’ acceleration figures compare tolerably with the similarly engined but manual gearboxed 6-Series Coupe E24, a fact that may go some way to explain why no tester mentioned he would have preferred to drive a manual gearbox car.

The engine and transmission provide a smooth strong surge of acceleration throughout the nor-mal speed range. At 100 mph the 735i is ambling along with the engine turning over at 3,200 rpm, and at 120 mph (3.800rpm) it is still a relaxing car to travel in – if still not quite matching the low noise levels found in an Jaguar XJ12 HE saloon. Mechanically the 735i is a gem. However, there remains one important criticism and that relates to the selector arrangement. On the one hand it lacks a ‘ stop’ to prevent the inadvertent selection of neutral when changing up, yet there are stops to be overcome (by raising a catch on the underside of the lover) when downshifting to 3, intermediate or low gears. What is really required is gating that allows free movement between 4 and 3 (since this is a frequently used change across which the engine cannot be over-revved) and guards to protect neutral, 2 and 1. As with all fuel injection BMWs cold starts are immediate, and warm up driveability superb.

Economy

20 mpg for the asking

For the post 1982 E23 735i automatic to achieve 19.6 mpg overall under road test conditions is a creditable performance considering the size, weight and performance of the car and this figure compares interestingly with the previously tested 735i manual’s 17.3 mpg.

During the test period fuel consumption varied in an unusually narrow band between 19 and 21 mpg, perhaps reflecting the consistently hard usage the car had. We would imagine these who are prepared to drive with e tolerably light foot, let the gearbox change up early and cruise below 90mph will never see less than 20mpg. Figures of this order in conjunction with a larger 22.4 gallon fuel tank (previously 18.7 gallons) give the 735i E23 a range in excess of 350 miles, which is as it should be on such a car. As before there are no irritations at the filling station and it takes only a few seconds to bring the fuel level to the filler neck for a true brim. A thoughtful detail is the clip on the inside of the filler cover to hold the cap. Oil consumption during the test period was negligible.

Noise

Not much

There is little doubt that in addition to making the 735i a more efficient motor car, suspension and aerodynamic alterations have made it more refined. Road noise comparisons are difficult since the previous 735i E23 used ultra-low profile Michelin TRX tyres. That car produced a noticeable degree of road generated tyre rear on coarse surfaces whereas the low level of tyre induced noise in the new car barely increases except on the very roughest motorways. Bump-thump and some rumble occasionally intrude when running over road joints and potholes, but never to an upsetting degree. As on the previous model one can be confused into thinking wind noise is worse than it really is if the face level “vent” control is selected, the through flow causing a rustling noise in the facia vents. Outside wind noise is well suppressed but does gradually rise in line with speed, once the car is doing anything over 80 mph. The engine is a delight, not only for the way it goes, but its silky smoothness when revved hard. Then the sound emanating from under the bonnet is a delightful blend of well-tuned induction and exhaust systems; quite muted but very sporting in character, while on light openings there is nothing more than a murmur from under the bonnet.

The overall impression is of a very refined car in which one can converse or listen to music between 100-110 mph without raised voice or hindrance.

Road behaviour

Better but still skittish

At first acquaintance the 735i’s unchanged power-assisted recirculating ball steering might be taken as boing lower geared than the norm, until one discovers the car has a usefully tight mean fore we must compliment the quality of the latest BMW’s steering. It is heavier weighted than most (particularly in relation to the Jaguar XJ6) and gives remarkable feel and precision for a non rack and pinion system.

Even at normal driving speeds the better behaviour of the new car is immediately obvious. Cornering roll and “squat” under hard acceleration are reduced and the car has an altogether tauter feel than the previous model, with noticeably improved straight line stability – which incidentally gave no cause for concern on wet roads at 100 mph in some of the windiest conditions experienced for some time.

Facia details from right to left – all systems check panel (see inset), main instrument binnacle containing rev-counter, water temperature and fuel contents gauges, service indicator, and speedometer (plus usual warning lights)  and in the centre, heating and ventilation controls, radio/cassette, on board computer, speaker balance control, rear mist switch and cigar lighter and very generously sized ash tray. Main lights and lamp switches are either side of column on facia. Stalk controls work indicators/ dip/headlamp lash on left, the upper right switching the wipe/wash, and by lower one the cruise control. Wheel spoke mounted presses operate horn.

Nor should there be any cause for complaint where ride quality is concerned, especially now that the new rear suspension is less affected by varying load conditions. The car soaks up the worst B road surfaces with great competence, and where there are bumps and changes in road camber the car faithfully holds the chosen track.

That said the suspension changes seem to have resulted in very little change in the car’s overall balance. There is the usual eager response to steering inputs, and on dry roads the car simply goes where it is pointed, ultimately breaking away front and rear together. On dry roads any significant loss of rear end adhesion can only be provoked by lifting off when cornering loads ere at their very highest, and then the slide is a simple matter to correct. As mentioned, the test car was fitted with a limited slip differential. On wet roads its action certainly inhibits wheelspin during sharp getaways or when accelerating out of a slow corner; by the same token, the insensitive driver may find the driving torque (of which there is a considerable amount) pushing the rear of the car sideways, rather than any of it being released via a lightly-laden spinning inside rear wheel. The skilful may relish this ability to control the car’s attitude with the throttle wh8n the roads are slippery, but it is a big car which takes space and practice to collect neatly from a wide angled slide. Oversteer of this nature could be less dramatic (even if it occurs at a lower cornering limit) without the locking differential. Suffice it to say that although the latest E23 735i is a more stable car, with more predictable handling and better ride than its predecessor (pre-1982 E23 7-series), the rear end remains rather too easily upset by coarse handling on slippery surfaces.

Whatever shortcomings the 735i may still have in balance, it can barely be faulted in terms of its braking abilities. It comes with the Bosch ABS anti-lock system as standard. For the uninitiated it is worth mentioning that under ail normal driving conditions the brake pedal feels quite normal with an averagely weighted pedal. Retardation rises pretty well in line with effort until the brake locking point (at between 50 and 60lb effort depending on the conditions) whereupon the pedal can be pressed as hard as one likes (to the accompaniment of a pushing back pedal and graunchy noise) without detriment to the crash stop performance: moreover because the system keeps the wheels turning, fairly dramatic avoidance manoeuvres can be made in confidence while braking very hard, even or bends.

Front seats are generously proportioned, strongly upholstered an widely adjusted (as are head restraints), in the case electrically via two panels and eight push button switches in centre console. In addition to front door pockets, stretchy pockets are provided In front soot backs. Rear legroom is generous. Seat belts and head restraints are provided and lidded centre armrest locker contains first air kit.

Strangely, we were only able to manage a best crash stop performance of 0.9g (as opposed to 1.0g before on the TRX-shod car but this could be repeated again and again without any concentration whatever on the driver’s part. One begins to take the car’s “idiot proof” stopping on wet roads for granted, and assume those following are skilful enough to match the BMW’s abilities. A useful warning to those following would be to badge ABS equipped cars “Anti-lock”. As before fade resistance is adequate for the performance of the car and towards the final stops in the deliberately severe Autotest fade test (10 consecutive 0.5g stops from 88 mph – the speed achieved at the ¼ -mile post) there were signs of a recovery in pedal efforts after a fairly sharp rise during mid-test. The handbrake held the car on the 1 in 3 (from which the upward facing restart was accomplished with ease) and managed a typical 0.3g retardation on the flat.

Behind the wheel

Few changes

Existing BMW 7-Series E23 owners will notice no fundamental changes in the new models except for the slightly redesigned instrument binnacle. There is a plethora of “extras” in the standard specification, to which an equally long list of options can be added.

Our seats were electrically adjustable for height, rake, whiplash restraint height and stretch, via four clearly labelled groupings of four switches (two groups per seat) mounted behind the T-handle selector in the centre console. The electric window switches are mounted behind these, the niggles here being that it is all too easy to rest an elbow on one switch or the other, (recessing them would help) to find a window opening or the seat moving as if by divine force!

On first acquaintance the seats seem hard, but they support extremely well over long distances, and no tester had cause to complain of discomfort, or difficulty in finding an adjustment to suit his frame. The steering wheel is also movable for reach, and there is enough rearward movement to accommodate drivers of at least 6ft 4in. in height. All-round visibility is good, apart from blind spots caused by thickish front and rear pillaring; however, a tailor driver’s view of the main instrument dials is partially masked by the steering wheel rim. The stalk controls are nicely positive in use. The left looks after indicators, plus dip and headlamp flash, with the upper right working the wash/wipe controls, which have two speeds plus intermittent and flick wipe, which triggers the powerful four-jet screen wash and linked wipe facility.

One tester mentioned finding himself occasionally confusing the latter stalk with the one operating the cruise control, which is the same length and set only a few inches beneath it. In contrast the facia mounted main lights and front and rear fog lamp switches cannot be fumbled.

Bonnet opens to vertical position and is hold conveniently by gas-filled struts. BMW’s largest straight six M30-engine (M30B35), and associated fuel injection equipment fits in the tittle space to spare. Layout is nevertheless neat and tidy, with all fluids (except oil) in transparent check-at-a-glance reservoirs.

On the far right-hand side of the facia is the by now universally fitted (on up-market BMWs) press-button systems check display dealing with engine oil, brake fluid, coolant and screen wash fluid levels, pad wear, and rear light bulb failure. The old E23 7-Series also incorporates the electronic “service indicator” whose beautifully neat display of five green lights then amber and red (service essential) is set between the water temperature and fuel contents gauges. Also displayed in the main instrument binnacle are the usual warning lights plus one relating to any failure in the ABS – in which very unlikely event braking simply reverts to a conventional system.

Grouped in the centre of the facia are the heating and ventilations controls plus such items as the radio, and its front/rear speaker balance control, cigar lighter, rear demist switch, and the by now well publicized BMW on-board computer, which in addition to providing facilities for every conceivable time, distance or average mpg (within five per cent of the truth) calculation, and can warn via a chime of exceeding a pre-set speed, work as a stop watch and when suitably programmed act as an ignition lock and alarm via a driver-set four figure code.

BMW’s system of push-button internal airflow controls (each dealing with a separate function) works well, particularly in the “demist” mode which automatically directs most of the air blending system’s output directly to the screen and side windows (via door ducts) and switches the fan to the fastest of four speeds. Temperature control (via a turn-wheel graduated from one to 10) and output are satisfactory, the only minor niggle boing that in common with many other currently available air blending systems, the centre and top facia vents are “semi-sensitive” to the temperature control, moaning that face level fresh air is only available with the temperature control adjusted at around the halfway point or below. A directionally adjustable centre mounted warm air outlet is provided for rear seat passengers.

Living with the 735i E23

It is a complex cockpit, but clearly laid out, and comfortable, nor should rear seat passengers have anything to complain about. The seats are well shaped. Log and headroom are generous and rear head restraints and seat belts are provided. Nice features are the neatly recessed rear scat bolt buckles, and the first aid kit contained in the lidded centre arm rest. The driver will particularly appreciate the headlamp wipers operating with the screen wash at night, the headlamp levelling system worked from a drop-down panel in the facia, plus the automatic dimming of the heating and ventilation switch gear lighting when the main lights are switched on.

There is an interior light delay. Both door mirrors are electrically adjustable of course, and depending on which way the relevant rocker switch is pressed, the optional sunshine roof either tips or opens conventionally. The radio aerial is power operated, and the central locking is of the quieter electro-pneumatic type and it also secures the fuel filler cover. The vanity mirror on the reverse side of the passenger’s sun visor is illuminated. There is a decent sized glovebox, two centre console trays, a recessed facia top, front door bins and stretchy pockets in the front seat backs, so space is adequate for housing most travelling paraphernalia. All the upholstery and carpeting is of high quality material and some very tough rough woven mots are provided. The boot is huge, in spite of the fact that the wheel-arches and vertically mounted spare wheel do intrude noticeably.

The usual comprehensive BMW tool kit is contained in a drop down tray mounted on the inner side of the boot lid. Another piece of thoughtfulness is a wiper pattern converted to right hand drive, the one vestige of the European specification car being the sturdy over-centre action bonnet release lever mounted on the passenger’s side kick panel. The bonnet hinges forward and is propped by gas struts to reveal a very crowded engine bay. Regular checks of fluid levels and fuse replacement are straightforward enough thanks to transparent containers, but with all the engine’s functions under electronic management there will be little or nothing even the knowledgeable owner can do to help himself in the unlikely event of a failure occurring. In our experience of a BMW 528i E28 long-term the service indicator will dictate the need for garage attention every 7,000- 8,000 miles.

The BMW 7-Series E23 range

The 2.8-litre E23 728i costs £14,320 (£14,680 auto – 1983), the 732i £16,090 (£16,450 automatic ZF – 1983) and the subject of this test, the 735i, £18,500 or £18,860 in automatic form (1983 ZF4HP). The E23 BMW 735i SE version costs £23,300 and incorporates many of the options tested here as standard equipment.

The traditional BMW boot lid mounted toolkit is always a welcome sight, end the boot itself is very generously proportioned, even after the inclusion of a vertically-mounted spare wheel.