ECONOM PLUS
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by John F. Moon,
A.M.I.R.T.E.
The Latest Import from Germany is the Borgward Express Microbus : Seating for 12 Persons and Remarkable. Fuel Economy can be Bought for £862
QNE of the latest marques to he imported from Germany is the Borgward Express Microbus, the concessionnaires for which are Metcalfe and Mundy, Ltd., 280 Old Brompton Road, London, S.W.5.
The performance, capacity and general finish of the Express are exceptional, especially in view of its retail -price of £862, but its most remarkable feature is its fuel economy, and the secret lies in the use of a tWo-cylindered two-stroke petrol-injection engine.
This unit ,is little bigger, than some current motorcycle engines, having a capacity of only 688 c.c., but it develops 29 b.h.p. at 4,000 r.p.m. and has a high torque rating of 43.2 lb.-ft. delivered at 2,600 r.p.m. The reason for this abundance of power and exceptional fuel economy (the specific fuel consumption at 4,000 r.p.m. is 0.51 lb. per b.h.p.-hr.) is the fuelinjection system.
Petrol Injection System Bosch equipment is used. It consists basically of a conventional plunger injection pump, operated by cams integral with the crankshaft and supplying fuel through injectors in the cylinder head. The injection pump has .a diaphragm governor controlled by a venturi in the inlet manifold, and lubrication of the pump and engine is catered for by an engine-driven oil pump which draws its supply from a separate oil tank.
Some of the feed from this pump passes into the injection pump and some continues to a pressuresensitive control valve in the airintake manifold, through which it is fed, with the airstream, into the cylinders. There is no oil-return. thus a constant supply of fresh oil is ensured.
Other features of the Express include a four-speed all-indirect synchromesh gearbox and final-drive unit which is transversely mounted in unit with the engine, below the forward bench seat. The drive is taken to the front independently sprung wheels, and the absence of a transmission line to a driven rear axle provides for a low floor.
Welded Steel Body
The body of the Microbus is a steel welded assembly, although timber flooring is used. In both van and Microbus form it has double doors at the near side, a large rear door and a door at each side of the driving compartment, which is ahead of the front wheels. The Express is also available as a pick-up, in which case the retail price is £800 14s. 8c1.
My tests were extended over a period of six weeks, because when I first collected the Microbus from Metcalfe and Mundy. Ltd., it had covered only 475 miles, and I was warned that the engine would not give of its best until at least 2,000 miles had been put on the clock. At the end ofthree days concentrated driving I had managed to increase the mileage by only 650, and although the average fuel-consumption rate was good I decided to return the vehicle to the concessionnaives and collect it later.
With 15 cwt. of iron weights to represent a payload of 11 passengers and light luggage, Succombs Hill was attacked during the first series of tests .and this was sufficient to convince me of the exceptional power developed by such a small engine.
Three climbs were made in low gear at 15 m.p.h., and at the end of the third climb the radiator temperature had risen by 20° F. to 190' F., the ambient temperature being 52' F. A stop-start test on the 1-in-4 gradient failed, but subsequent attempts on a 1-in-5 slope proved successful and the hand brake comfortably held the vehicle on the steeper gradient.
Brake-fade tests were made during the descents, and although the pedal travel had increased sufficiently to allow the pedal to touch the floorboards, a confident emergency stop was made from 20 m.p.h., after the third descent. The increase of pedal travel was in fact not so marked as at first appeared, because the normal full application brings the pedal to within 11 in. of the floorboards when the drums are cold. the master cylinder having a long working stroke.
After four weeks of demonstration work, during which period the engine had been decarbonized, the Microbus was ready for further tests, and these were conducted in the Midlands. A run between London and Worcester, a distance of 110 miles, was made at an average speed of 39 m.p.h. and an average consumption rate of 31 m.p.g.
En route to Worcester it was necessary to descend Fish Hill, which is 11 miles long and has a general gradient of 1 in 14.2. Third gear was engaged and the brakes partially applied to restrict the speed to 30 m.p.h. and at the bottom of the hill there were slight signs of fade, but the brakes soon recovered.
Acceleration runs were made along the main Warwick road near Solihull and I was glad that the gear change had eased off a little since I last had the vehicle. During the first tests the change was so stiff as to cause severe arm-aching on a long journey, and was not improved by an over-efficient baulk-type synchromesh mechanism.
Low, second and third ratios only were used for the standing-start tests and correction was made for a speedometer which was 121 per cent. fast, similar corrections being necessary for the odometer during subsequent tests_ Changes were made at the maximum speed in each gear, as indicated by marks on the speedometer dial.
There being no direct drive in the gearbox, third gear was used for the rolling-tart runs, and between 10 m.p.h. and 15 m.p.h. slight movement at the steering wheel betrayed the high torque transference to the front wheels. This effect was even more marked when pulling hard in the lower gears, especially when cornering, but is a characteristic of other front-wheel-drive vehicles.
Braking tests were made along a reasonably rough-surfaced road off the main traffic stream and despite the relatively small facing area ot 112 sq. in., satisfactory figures were obtained. ( would have preferred a more "solid pedal, . because repeated adjustments and bleedings had failed to remove its sponginess. For a vehicle which can be expected to run at speeds in excass of 50 m.p.h., a greater frictional area would also increase safety.
Fuel-consumption runs were made over a give-and-take course in the Meriden-Stonebridge area. The circuit included several steady up-hill grades—one of which required third gear—and three roundabouts. The same stretch of road was used for refuelling on each occasion, and to avoid the risk of air-locks causing a false result. I disconnected the fuelreturn pipe from the filter-where it entered the front end of the tank and added petrol to this level. The figures obtained were the result of two runs under each condition and must surely create an economy record for a petrol-engined vehicle. The speed during each test was not allowed to exceed 35 m.p.h. and, as can be seen from an accompanying table, provided that the Microbus can be kept on the move in top gear, the amount of fuel needed is extremely small.
High sensitivity to variations in n1 3
load, and to constant stopping and starting, is shown by the marked differences in consumption rate returned after each test. The engine had been set to run on premiumgrade benzole mixture, which was used throughout the 400 miles of testing, and an overall consumption rate of 29.4 m.p.g. resulted. This mileage was covered with a full payload, except when making the shortdistance fuel runs, and consisted of high-speed long,distance trips and short runs in built-up areas.
Warmington Hill, near Banbury, was climbed when returning to London. It has an average gradient of 1 in 9 and-was climbed in second gear, the speed dropping to 15 m.p.h. on the 1-in-7 section. The temperature rise was only 10 F. above the normal figure of 170° F.
The Borgward is not particularly light to handle. The large-section tyres and relatively high front-axle loading combine with the normal resistance caused by the front-wheel drive to produce heavier steering than is usually found on British vehicles of this size.
Dia Similarly, the gear change, which is from side to side because of the transverse gearbox, is not fight, although the synchromesh is of a high standard, which is a slight compensation. Even when braking gently, a heavy pedal pressure is necessary.
On short runs, this general heaviness would not be of sufficient moment to worry most drivers, but 1 would not like to suggest that a woman driver should be expected to handle .,the laden vehicle for more than 100 miles without a break. A further point is that the large turning circle can be troublesome in traffic.
The wide cab doors give easy_ admission to the driving seat from each side and the high driving position and generous glazed area provide excellent all-round visibility. The suspension. is good over any road surface and pitch and sway were not marked at any time. On wet roads the front-wheel drive gives a stability which permits high-speed cornering with confidence.
The front-seat cushions provide the sole insulation from engine noise, and for this reason occupants of the Express are always' conscious of the high-pitched snarl of the power unit. This is not irritating and does not prevent normal conversation in any part of the vehicle. The external exhaust note is, in fact, appreciably louder than the engine noise experienced within the body.
To obtain the best performance from the Borgward it is necessary to keep the engine speed high. Although the power unit pulls well at low speeds, its effect on the transmission can be clearly felt through the steering wheel and the sluggish acceleration rate provides a useful reminder to engage a lower gear.
Seating fOr six passengers on the off side and four on the near side is arranged longitudinally, with room for one alongside the driver. The seat adjacent to the double side doors can be folded up and this leaves a large clear floor space for luggage. The accommodation suggests that one of the many uses to which the Express could be put is that of transporting a cricket team complete with gear. Ventilation is somewhat restricted, being confined to sliding windows and hinged quarter lights in the cab doors and two large extractor lights towards the rear of the body. In hot weather the temperature inside the bus can rise uncomfortably.
Other standard fittings which illustrate the high quality of the vehicle include a most efficient heater and demister; two interior lights and winking direction indicators.
For use in Great Britain, additional steps are fitted at the side and rear doors to reduce the single-step height.
The step on the near side forms a minor driving hazard by increasing the width of the vehicle by 4 in. Its height is such that it can easily foul a high pavement. A light-alloy luggage rack is available as a roof fitting for an extra £24.
My first maintenance task was to adjust the brakes, which took 12 minutes. The time included assembling the mechanical jack, jacking up each wheel, finding the correct spanners and locating the two adjusters on each brake back-plate. The jack is a quick-acting unit which makes lifting a laden vehicle somewhat too much like hard work.
Bleeding the system took 10 minutes, with an assistant to pump the pedal. The reservoir is reached through a trap in the floorboard in front of the passenger seat and its position enables the pumper to watch the fluid level from the driving seat.
This trap would be improved by a screw fastener, because when travelling fast the air builds up under the floor and lifts the trap and rubber mat which covers it.
To jack up and remove a front wheel and fit the spare took six minutes. The spare wheel is a tight fit under the rear of the body And a certain amount of juggling is necessary to remove it. A brake drum was removed while the wheel was off, so that the facing area could be measured.
When the two scat cushions in the driving compartment are lifted, the engine is completely exposed for all routine maintenance tasks.
A clean-air intake and silencer is essential with a high-efficiency twostroke unit, and removal of the Borgward fitting is an easy matter, entailing the slackening of a clamp ring and a cylinder-head unit. The filter element is retained by two snap fasteners. With the silencer removed, complete access is given to the starter.
The petrol filter is well placed fol attention and a single bolt secures the filter bowl. With the bowl removed, the disc element may be lifted out by the wire handle for washing. When the filter had been reassembled it was primed by turning on the ignition and thereby working the electric lift-pump. This whole operation occupied five minutes.
Distributor Adjustment Easy
Although the distributor is sited behind the engine it is easy to reach, and adjustment of the contacts is reasonably simple. The injectors and sparking plugs are located in the top of the cylinder head and to remove the injectors it is easiest to take out the plugs first. To remove, clean and replace both plugs and injectors is a 10-minute task.
The engine-oil filler is in the front panel alongside the radiator filler and both are concealed under a hinged flap. The gearbox filler is partly shielded by the air cleaner and this must be removed unless a pipe is used as an extension to the oilcan.
There are 33 greasing points and all are reasonably accessible, with the exception of the nipples on the inner universal joints of the drive shafts. Topping-up the rear dampers is not easy, because no traps are provided in the floorboards to give access to the filler plugs.