Category: New cars

The Law Of Chisholma-Benz

Video: The Law Of Chisholma-Benz
Video: Betz' Law proof and explanation 2023, February
The Law Of Chisholma-Benz
The Law Of Chisholma-Benz






No matter how scolded electronics, the Internet is a great thing (when it is on the desktop, not in the car). We decided to find out what exactly from electronics broke and caused reviews from different companies in recent years. Here is an impressive list of sometimes very curious defects:

1. Renault Espace 1996–1998 - A defect in the cable for the winch lifting the spare wheel could lead to the loss of reserve on the go.

2. BMW 3 - 7 series 2000-2001. - overheating of the electronic block of the cooling fan created a risk of overheating of the engine and even ignition of the fan itself.

3. SAAB-900 of 1995, "Lancha-Fedra" - airbags spontaneously deployed.

4. “Lancia Thesis” - the steering wheel angle sensor could cut the ESP system on the go and take the car off the track.

5. "FIAT-Steel" was noted directly at the service station, hitting technicians on the ears with side cushions when they connected the instrument cluster after the repair.

6. Last summer, BMW appealed to the owners with a request not to drive around on vehicles with V8 and V12 engines (release from May 13 to July 12) due to a defective controller.

7. And here at "Subaru" nowadays "Legacy" and "Impreza" 1997-1998 suddenly "malfunctioned". - a sharp press of the horn button could activate the pillow squib …

“Everything that can go bad goes bad.”

The First Law of Chisholm


Martina Muller drove up to the next intersection at a speed of about 40 km / h. The red light came on, and … the brake pedal suddenly fell under my foot almost to the floor. The usual slowdown of the Mercedes-E320 did not follow, although the lady frantically pressed the pedal. Martina, an experienced driver (annually drives 30, 000 km), remembered in time about the additional pedal of the parking brake, and it worked almost at the edge of the intersected street. Of course, Frau Muller replaced the controller for controlling the SBC intelligent system, but now it never accelerates above 130 km / h (this is in Germany!), Constantly waiting for a catch.

Such cases, alas, are not isolated. For example, Danish taxi driver Dan Petersen was “lucky” to experience the SBC’s refusal three times and finally, by the grace of the electronics, lose the rear bumper - a crash occurred during a U-turn.

So began the largest action to recall the Mercedes with an advanced electronic brake system - in total 680, 000 of these cars managed to leave the conveyor! And there wouldn’t be anything special - reviews today are like advertisements (they say, we care about the client!), If it were not for the unprecedented decision that followed - stop installing SBC and return to traditional brakes.


We recall briefly that the Sensotronic Brake Control, which worked in the new E-class, as well as in Mercedes-SL, SLR and Maybach, is nothing more than brake control "over the wires": the pressure in the drive does not create driver’s foot (even reinforced with vacuum), and a separate hydraulic pump. The driver only gives the command to the computer, and it opens and closes the necessary valves, and for each wheel separately. This takes into account many factors and parameters of the car. As a result, when everything works as it should, braking is effective and safe.

If the first Chisholm law comes into force, then the red STOP sign lights up in the instrument cluster, the vehicle speed is limited to 90 km / h and the emergency circuit for the front (only!) Wheels is highlighted in the brake system. And the same as it was on cars of the 40s: without any amplifiers, ABS and other stabilization systems. It is not surprising that the way to a stop increases by 30 meters (at 100 km / h) and the most unpleasant thing is that a malfunction can occur not only with a harmless reversal, like the Dane, but also on the autobahn at the highest speed. In this case, a polite warning of a computer about a risk runs a bit late.

Here we, perhaps, will leave alone a very reputable company and talk about


In a famous joke about Russian and American, bragging about the achievements of their car industry, our compatriot amazed the opponent that his car would reach home without any computers: "Where is he going to get out of a rut!". Perhaps there is some truth in this joke? After all, the more complex the system, the higher the probability of failure. Take a look at the table of electronics failure rates, their share in the total number of failures. Scientists have extended it until 2010, and probably their forecast is not so far from the truth. There is more detailed information on this subject, disaggregated by manufacturers. We will not dump all the information on readers' heads, but note: if the total number of failures corresponds to the brand reliability rating, then the share of electronics failures surprisingly fluctuates around 50% with slight deviations. This confirms that the problem is systemic, and the case with the Mercedes only showed it in a new light - car safety.

Recall the theory of probability: with the reliability of each electronic system at 0.99 (the probability of failure is 1%), the reliability of a car with six computers is only 0.996 = 0.941 (the probability of failure is already 5.8%!). By the way, there are about seventy controllers in Maybach!

Scientists have formulated the conditions when, even with electronic devices, the car would have a reliability level of 0.99 as a whole. It turns out that for this you need to create a “computer” with a reliability of 0.998 (the risk of failures is not more than 0.2%). Not only that, electronics of this level could turn Golf into Maybas for the price - it becomes obvious that the work of electronic engineers will be Sisyphus. As soon as they set out to determine the next (7th, 8th, etc.) new product under the hood, immediately there would be super-demands on the reliability of not only herself, but also the previous six. Otherwise, the problems will grow like a snowball!

But perhaps it is not necessary to multiply and complicate the electronic filling of the car? What, by the way, do car owners think about this - after all, only they, in the final analysis, have the right to decide what they need and what not. The answers given on the diagrams to the three main questions are very eloquent.

Well, everything is clear. And why only our “frets” are notorious for being the most reliable in the world?


They have long been brought into endangered species. But in vain: in some places it would be worth creating reserves! As proof of a couple of recent stories. Imagine: speed under 80, you are in the tunnel. And suddenly … the motor stalls, the power steering and brakes fail, the warning lights and instrument arrows start a frantic dance. Horror! Well, at least the car by inertia overcomes the area with evil spirits and everything normalizes. Such an incident occurred with Franz Elmiger in the area of ​​the Gubrist tunnel near Zurich. His "Scene" was changed by "brains", but everything repeated the same way. Then a technician of a service center with a diagnostic laptop sat nearby. O-pa - the computer was cut down along with the car controller! Similar jokes in this damned place and competitors - "Peugeot 406". “Something is floating in the air, probably some unacceptable mixture of radio waves for the French,” was the verdict of experts.

But in Germany, next to the Bundeswehr medium-wave transmitter, local residents still prefer … carburetor cars without anti-theft systems. Firstly, they are not already being stolen, and secondly, the doors do not lock on their own. Injection cars do not live here for a long time - they’re going crazy. And this despite the billions that automakers spend on electromagnetic compatibility research - it is clear that not all combinations of fields can be modeled in the laboratory …

However, in some places on the ignorance of visiting drivers, you can earn. In a German village, for example, there is a tricky ATM that doesn’t let go of a car parked nearby: it just jambs it. A resident of a neighboring house, without thinking twice, bought a tow truck and does not know any downtime: a dozen poor people help out a day.


This eternal question was asked by the world's leading manufacturers of automobiles and components. Of course, no one seriously thinks about returning to the carburetor past - there are too many advantages for motors controlled by electronics. Even the military, which traditionally considered mechanical systems more reliable in the event of a nuclear explosion that completely kills microcircuits with an electromagnetic pulse, has long given up. But to make electronics a truly strong and persistent link in the hierarchy of automotive devices is an imperative of the time.

The Daimler-Chrysler acted as the skirmisher of the new initiatives. Here they set about developing the so-called “zero-defective culture” of production, which is based on a number of commandments and future standards. Now manufacturers of components will be certified on a five-step scale: only climbers to the fifth, highest level will be able to claim the supply of chips for the Mercedes.

Hastily developing standards and new rules of the game for manufacturers of automotive chips, and they will be tested in the complex of all electronic filling. After all, the connections between the systems today have become so complex that defects can appear precisely during the abnormal interaction of individual controllers.

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