I have read on several german web sites that Mercedes is having problems with the new E-Class; 50% of all warranty claims are to do with the engine management system and Bosch are working flat out to address the problems. There has been a 'problem solution' working group for about a year now.
There are also problems emerging with the SBC electronic brake system; details are very thin so it is not possible to describe what the problem is. I have read in 'What Car?' of one reader who suffered several complete brake failures with his new E-Class; DaimlerChrysler replaced the vehicle but refused to acknowledge there was an issue (they stated that the diagnostic memory did not record any such event).
Look in here (in German)
automobilwoche.com
-But if there are serious problems with the new E-Class you do not need to be a genius to work out that DaimlerChrysler will not admit to anything they do not need to: with the new new 5-series available it would be disastrous if word got out that the E-Class has suspect brakes or electronics.
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The SBC system worries me - it looks a bit too clever for its own good! I hope they did a damn good FMEA on it.
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Take a look at
www.honestjohn.co.uk/forum/post/index.htm?v=i&t=57...6
I quote from one of the posts of Mercedes own press release
"Only in the event of a major fault or power failure does SBC automatically use the services of the tandem master cylinder and instantly establishes a direct hydraulic link
between the brake pedal and the front wheel brakes in order to decelerate the car safely."
I like the idea of 'instantly establishes,' in the real world it is either already established or it takes a finite (albeit short) time. I could be generous and say something has been lost in the translation from German, but there again it is more likely to be PR spin.
If complete failures have actually occurred this system obviously is not 100% foolproof!
pmh (was peter)
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pink fluffy dice.
Sigh, when will people learn not swear. Far easier to delete than edit, btw. DD.
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I was a little bit worried about the brakes on the E-Class when I was looking at buying one so I did a bit of research. Apparently to produce a car with this type of system Mercedes had to get it approved by several institutions and so on. The independant tests were that a conventional system was 30% more likely to fail than the SBC system.
Sounded so good I bought one and I am very pleased with it.
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"a conventional system was 30% more likely to fail than the SBC system."
Y'know, I never quite understood those stats. The way I see it is that the SBC is essentially a fairly standard braking system but with a very clever way of connecting the driver to the stopping bits :)
If this is the case (and if I'm not completely misunderstanding it all, and just blithering senselessly), you'd have precisely the same scope for mechanical failure at the business end, but with the added possibilities of failure in the flashy new electonics.
I'd also be a little concerned that the system (especially given the use of a pedal travel simulator component) could effectively disguise potential problems with the brakes that you might normally feel through the pedal itself.
On paper though, it packs a lot of great functionality in - it'd be nice to be reassured that it does indeed work well and with greater safety figures.
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"a conventional system was 30% more likely to fail than the SBC system."
This is straightforward marketing nonsense. Basic reliability theory says that as you add elements to a system it becomes more unreliable.
Mathematically, the overall system reliability, R, as a function of time, t, is given by:
R(t) = exp-(r1+r2+r3+...)t
Where r1, r2 etc. are the reliability coefficients of the individual components. It is impossible to build a more complex braking system that is more reliable than a simple system (using the same basic braking components).
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Erm... yeah, that's what I meant to say ;)
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The story in automobilwoche sept 15: "Mercedes pulls the brake".
MB are pulling out of SBC for economic reasons. Bosch said "we told them so. the volumes are not high enough...".
The existing hydraulic systems will be enhanced...
Looks like Blair is not the only one without a reverse gear !!
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Would the SBC system not work in a very similar way to aircraft " fly by wire" systems?
How reliable are the systems used on planes?
The answers are yes and very. Well that's what I've just been told.
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Damn I wish I could read German.
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Marcos, there are, of course, a number of fairly good german - english web-based free translation facilities available these days. Google have one. You can either cut and paste text or provide a url. Whilst far from perfect, this facility will provide a good gist of the content. It copes less well with technical stuff though.
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aircraft " fly by wire" systems...
reliable but triplicated! How many car companies are going to pay for triplicated redundant systems, with majority voting logic monitoring? In the early days, duplicated electronic systems were implemented using different manufactures processors with code written by independent software teams! I like to think that this still applies but somebody will know.
Interesting if Mercedes have dropped the idea...
pmh (was peter)
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You are right - aircraft systems are triple redundant with majority voting and have to pass very stringent FAA and CAA certification tests. None of this applied to automotive systems.
Even aircraft systems still can go wrong (I don't think the Paris Airbus crash was ever fully expained - the pilot blamed the computer, I think).
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With regard to reliability stats can I pose following queries
1: If climbing with 1 rope with 1 in 100 change of failing I understand the risk
If I climb with 2 ropes with both @1 in 100 failing surely my risk is now not 1 in 100 but 1 in 100 times 1 in 100 ie 1 in 10,000 not sum of reliability as described earlier.
but statistics can be funny .
No plane has ever crashed with 2 bombs on board
Moral
Always carry your own.
You may be in prison for 20 years but you will be alive!!!
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Geoffken, it depends whether the ropes are in series or in parallel. Your example is for parallel i.e. climbing with safety rope. It is a different formula if your ropes are in series i.e. tied together to make one long rope.
No plane has ever crashed with me on board. No need for bomb.
Motoring link - no car has crashed with me on board (for last 20 years). ;-)
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geoffken
If you are referring to the little equation I posted earlier then you've read it wrong. The reliability coefficients of the component parts are 'powers'. The total reliability coefficient of the system is given by the natural log (e) raised to the inverse power of the sum of the component reliability coefficients.
I can assure you that it is correct.
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Geoffken,
With two ropes performing the same job you are considering two separate systems rather than increasing a single, simple system to a single, more complex system.
Aprilia's equation refers to instances of the second, not the first, since in this case it represents that an increasing number of components involved in a single system can only increase the likelihood of failure.
Two separate systems duplicating the same task can indeed lower the risk of total failure, although not the failure of any individual part or failure of any one of the single systems.
Mark.
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I think you will find that many Military aircraft with a lot of bombs on board have crashed, specially during WW2.
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