Innovations From Daimler-Benz
Elsewhere in this issue, W.B. looks at the history of Daimler-Benz in Britain and “Matters of Moment” celebrates the company’s centenary which is also the centenary of the motor car. No company is more conscious of its past (and none has more reason for pride) and no company is more aware of the demands of the immediate future. It is Daimler-Benz which has instigated the “Eureka” project which calls for widely-based European cooperation to develop new technology and traffic systems in the face of American and Far Eastern competition. It also currently employs 10,000 people in Research and Development (split 65/35 between its car and commercial vehicles divisions) and this fact alone clearly states its attitude towards the future.
In early February MOTOR SPORT was invited to the company’s winter testing sites which are centred around a frozen lake at Arjeplog in Swedish Lapland, about 60 miles from the Arctic Circle. There, on carefully designed circuits created by snow ploughs and on nearby road circuits, we were invited to sample three new driving systems, each controlled by microprocessors, which demonstrated that Daimler-Benz’s R&D staff has been fully occupied in creating the company’s role for the next 100 years.
Daimler-Benz has managed to bring the future closer with three microprocessor controlled systems which form part of the second stage of microchip development as applied to cars. By the end of this year, it will be offering as options on selected models three new systems: ASD (automatic locking differential). ASR (acceleration skid control) and 4MATIC (automatically engaging four-wheel drive)
Most of us found the ASR system the most interesting.
ASR depends on ABS and looks at safety from a diametrically opposed viewpoint. Whereas ABS prevents locking, ASR prevents wheelspin and does so in two ways. When a wheel begins to lose traction, ASR ‘s sensors applies individual braking pressure to it and an electronic system reduces engine speed.
This means that on sheet ice, or with one side of the car on ice and the other on a surface offering higher friction, one can floor the accelerator pedal and the car takes off smoothly in a straight line and without any wheelspin for even at 60 mph the system operates before a driven wheel has completed a full circle. The demonstration cars were fitted with an “off” switch to allow writers to make direct comparisons. Driving in a wide circle without ASR, I found I could reach 63 kph before the car spun. With ASR employed the car reached 62 kph and stayed there even with one’s right loot floored. The system had sensed the limit, a warning light advised the driver that the limit had been reached and he should back oft, but the device prevented the car from going beyond its limit.
I’ve just described a party trick, for how many of us drive in circles on frozen lakes? Nonetheless it was an impressive demonstration. It was possible to over-ride the system by straightening the car to gain a few kph more and then turning in again. When this happened, efficient crews arrived in G-Wagens to tow you out of the snowdrift. The point is that you have to try hard to beat the system for when the warning light comes on, you really ought to back off.
When it came to driving on country roads with a fresh layer of snow on lop of compacted ice I found that driving fairly briskly in the 50-70 mph bracket the dynamics of the 500 series Mercedes-Benz are anyway so good that the system wasn’t needed and it only came into play when I consciously wanted to see what would happen if I floored the accelerator in a bend, something one wouldn’t normally do on snow and ice. What happened? Nothing happened. Actually lots of things were happening within the system, with electrical impulses instructing the hydraulic pump which operates the brakes and the throttle being held back until the rear wheels would accept the notional power being delivered by one s right foot, but nothing communicated itself to the driving compartment.
Like ABS, ASR is something you hope you’II never need but, like fire insurance on a house, you’re glad you’ve got it when the need does arise. With it you can cross mounds of snow knowing the car will be stable and worrying about black ice is a thing of the past unless you happen to be driving like a lunatic in the first place. It doesn’t alter the laws of physics but it does enable the driver to more easily approach the limits laid down by physical laws.
We were treated to a demonstration by commercial vehicles with and without ASR. No matter what the tonnage of the vehicle was, the one employing ASR was quicker off the line so from the motorist’s point of view it could one day spell the end of lorries driven by lead-booted drivers slipping and sliding up icy hills.
Like ABS, ASR is not infallible when confronted with a maniac driver. ABS does not shorten optimum braking distances but then very few of us are capable of achieving an optimum braking distance in the first place. If you are driving sensibly and are suddenly caught out by ice, fallen leaves, loose earth or water on the road, ASR will come to your aid. If you’re miles two fast, it will still come into play but by that time you’re probably on your way to being wrapped around a tree.
To cope with extreme conditions when moving away in, say, deep snow or loose sand, the driver can operate a switch which changes the logic of the system to allow some wheelslip.
At present it has been refined only for some Mercedes-Benz commercial vehicles and for cars fitted with V8 engines. These latter all have automatic gearboxes and so far ASR has not been sufficiently refined to cope with manual boxes. To be fully effective it has to be individually tuned to types of transmission and the characteristics of the company’s engines. It will be offered as an option later this year at an additional 2,850DM or about £800 at the current rate of exchange and adds only 18 kg to the weight of a car.
The second new system is ASD which, like ASR, is controlled by sensors monitoring the wheels. Friction discs are incorporated into the differential and when the wheels start to spin a hydraulic unit compresses the discs to lock the drive. In effect this gives a limited slip differential up to 100% lock. As with the other systems a dashboard light warns the driver that the system is active and should there be a malfunction, monitoring circuits disconnect the system and another light warns the driver of the fact.
ASD is primarily an aid to directional stability when pulling away and it operates only at speeds below 37 mph. It disconnects if the brakes are used, for it is felt it is a disadvantage under retardation.
While it is not as spectacular as the other systems it has an obvious appeal for the sporting driver offering as it does many of the advantages of a limited slip differential. From mid-1986 it will be an option on the compact and mid-range cars and those S models fitted with six cylinder engines. It will cost 1539 DM (around £450) and adds an additional 15 kg to the weight of a car.
By far the most complex of the three systems is 4 MATIC, which is automatically engaging four wheel drive. Four wheel drive has suddenly become extremely fashionable and companies are vying with each other to produce models, in some cases to disguise the deficiencies of the handling characteristics of their front wheel drive cars. Four wheel drive is superb in difficult driving conditions but under normal circumstances, the majority of circumstances, a well-sorted conventional system is perfectly adequate.
Psychologically 4wd can lure a driver into a sense of false security and confidence and we’ve heard that in some countries which are habitually snowbound in winter, the motoring organisations report a high incidence of being called to stranded 4wd cars whose drivers have been so over-confident that they have felt they can drive anywhere. They have felt that their systems can break the laws of physics whereas even the best can only take a driver closer to the limits.
4MATIC has a transfer case from which power is distributed to the front and rear axles via a planetary gear-set and distributes power 35:65 with a rearwards bias. A computer monitors the rotation of the front and rear wheels, the steering angle and whether or not the brakes have been applied. Depending on how critical the situation is, it operates in four modes.
The first is rear-wheel drive only which is maintained for the larger part of anyone’s driving. Mode two is the 35:65 power split which is always engaged when pulling away and when driving if excessive slip occurs, it becomes engaged. Should this not be suflicient and the front and rear wheels are still rotating at different speeds, the central differential is locked (mode three), it all takes place in milli-seconds, less than an eye-blink.
Should this not be sufficient to keep the car stable, then the rear axle differential is locked (mode four). Should the driver apply his brakes, then the system is disengaged so that the ABS can work.
In practice I found that when approaching a corner too quickly and having the car slide, hitting the brakes brought it to a halt quickly but sideways on. Reproducing the same circumstances but applying power early in the corner took the car sweetly round, with all wheels driven, whereas in rear-wheel drive only mode, a quick spin resulted. I should say since we’re discussing safety systems, that I’m talking about driving on the lake where we were encouraged to drive to the limit and beyond and there were crews in G-Wagens on hand to tow cars out of snowdrifts.
Under artificial circumstances and without rival systems to compare under the same conditions, it is difficult to assess this system. ASR was easy to appreciate for it is unique, but it’s impossible to compare 4MATIC with, say. Quattro or Sierra 4×4 because l’ve driven neither on a frozen lake and nor, for that matter, on the sort of roads you find near the Arctic Circle in February.
Whereas with ASR and ASD you get what you pay for, and each is unique. 4MATIC will cost 12,400 DM (about £3,500) and we are suddenly considering serious amounts of money, especially when taxes are added.
Ford is able to provide an adequate, simple, 4wd system for roughly half that amount and since 4MATIC is initially to be offered only on six cylinder cars, there is a degree of over-lap in potential customers.
So far as one can tell in the circumstances under which the cars were tested, 4MATIC is a good and ingenious system but whether one needs something of such sophistication, and at such a price, is another matter altogether. On test tracks I found it possible to maintain much higher speeds than I would care to attempt when driving on snowbound public roads without ever engaging 4MATIC. That’s partly a compliment to the 300 series car I was driving and partly an acknowledgement of the fact that being let loose on a test track is not the same as being on public roads which have to be shared with average drivers who, by definition, are only average.
One question which hangs over all three systems, in varying degrees of force, is whether they do not encourage drivers to drive over their limits. The warning lights are supposed to warn drivers that they should back off, but some might regard the absence of a light as a carte blanche and others might see the light as a challenge.
A senior engineer assured me that they had modified the driving habits of the teams of engineers who had undertaken the testing but this appears to be empirical evidence gathered by engineers, who presumably began convinced of the excellence of their systems. I d be more convinced had the evidence been gathered by impartial assessors. A Swedish journalist told me how impressed he’d been by Mercedes-Benz’s organisation during the week before the press had arrived, “When something went wrong it was quickly put right.” he said. “all you saw next day was some glass on the road.” That doesn’t quite smack of modified driver-behaviour.
There must be a point at which so much assistance is given to a driver that he relies on “intelligent” driving systems at the expense of honing his own expertise. We all make mistakes and like ABS, all these systems could be useful when we have strayed over the limit, my fear is some people’s sense of security is going to be so enhanced that they will be less careful.
In time we will see these systems, and systems like them, become an everyday part of motoring. ABS, which was developed with Bosch, is exclusive to Mercedes-Benz for a little over a year before other companies may bid tor it. With mass-production the price should fall until it becomes, first, a widely-chosen option (as ABS has become on Mercedes-Benz cars) and eventually a standard fitting on certain ranges (like electronic ABS on Ford’s Granada Scorpio).
In the meantime, Daimler-Benz has regained its lead in automotive technology, albeit for a select market. The company which gave us the first 100 years of the motor car has begun its second 100 years in an impressive manner. — M.L.