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#451
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I am looking at an engine now where a design directive was given that there be fewer and lighter parts but with better NVH characteristics. Amongst other things, metal has been removed from certain joint areas. Fascinating.
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#452
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I recall talking to a gentleman who campaigned Porsches back around the time the 928 was newer. He was told not to race them. If he did factory support would evaporate for his team. Rod bearing 2/6 failures in the USA market and DNF's were apparently not part of a carefully groomed image.
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#453
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I love all those ads in North America about how you can pull a caravan with your S class. And how trailer hitches for sedans are factory options.
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#454
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Interesting to note Barry and Layback, as I tore down the engine from my '91 350SDL (which did not consume significant oil), and the pistons were level in the holes, but all cylinders were badly scuffed at 237,000 miles. The side-loads with the lowered wrist-pin were what I suspected as the cause, and I too wondered if this is a significant contributing factor to the ovaled cylinders and bent rods.
__________________
Gone to the dark side - Jeff |
#455
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Quote:
1) Click the troll's user name and select "View Public Profile" 2) Just below the name on the profile page (top/left), click the "User Lists" menu 3) Choose "Add to Ignore List", then click "Yes" when asked to confirm 4) Relax at the sound of silence. That reminds me of a quote I heard years ago: "When wrestling a pig in the mud, you both get filthy dirty. But the pig enjoys it." |
#456
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Ah, finally, some respite.
About five or six years ago I designed a windage control setup for the SRT4. Ed Peters (ex Chrysler failure analysis engineer) got one for dyno testing and insisted on paying for it. He carefully tested it at an oem level in his dyno cell. His comment: "this setup is the most significant bolt-on change for oil and windage control that [I have] witnessed since 1986" There is hope for a philosophy major after all. Edit: future readers of the thread, please do not let yourselves be browbeaten by some of the members here ... That they choose not to look should be of little import. Quote:
An inverse problem exists and many other theories can apply. There is great value in taking the time and effort to follow these alternate chains of reasoning. One never knows when circumstances will let you once again see an old friend. Good luck. Last edited by Kevin Johnson; 11-19-2010 at 07:49 AM. Reason: Follow up on chaos |
#457
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I have a 1991 350SD. Due to the high compression & poor design of the rods the engine blew 8 years ago. MB is aware of the problem & redesigned the rod to handle it.
MB paid for the repair. I now have 303k on the car. (The engine failed around 180K) I do Turnpike driving a lot in Pa. & cruise around 75-80mph. It runs great but uses a qt. of oil about 600 miles. |
#458
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My 200,000+ mile 603s never use more than a quart per oil change, sounds like your engine is again failing and might have a bent rod or two (or just ovaled cylinders). A 120,000 mile engine should not consume oil.
Did you buy the car new?
__________________
Gone to the dark side - Jeff |
#459
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What year was the motor replaced?
-J
__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket Tesla Model 3. 205,000 miles. Been to 48 states! Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels. 2014 Cadillac ELR 2013 Fiat 500E. |
#460
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Quote:
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#461
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Bending rods due to manufacturing tolerance issues?
Quote:
"Rodbender" rods being victims of tolerance issues during their manufacture -possibly explaining why some are weaker than others -is an interesting idea. In my line of work, I have encountered fabrication problems caused by a general lack of understanding of GDT (Geometric Dimensioning and Tolerancing) -a fairly recent dimensioning system that has been embraced gradually by industry in the last Twenty years internationally. My experience has been that when an Engineer/desinger first starts using GDT on his drawings it throws Manufacturing through a loop, often resulting in bad parts. The problem is also often compounded by the fact that Quality Assurance may also not understand GDT -resulting in bad parts passing inspection. GDT is a very good system once it is understood by everyone in the Engineering/Manufacturing/Inspection chain -but learning it can be difficult -and for those without strong spatial understanding, it may never make sense -but of course, those without strong spatial abilities probably should NOT be working in the Engineering/Manufacturing/Inspection chain anyway -but you'd be surprised how many there are who do. I wonder if the design and production of the "Rodbender" engine coincided with Mercedes Benz's initial incorporation of GDT, and the inherent teething problems that often occompany it? Last edited by clambake; 05-31-2011 at 02:03 PM. |
#462
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Does GDT include designing for the dynamic environment? I get the sense that the rods were incorrectly designed rather than incorrectly manufactured.
Sixto 87 300D |
#463
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No -GDT is a newish ('80's) dimensioning and tolerancing symbology used on engineering drawings, that allows Engineering to communicate a "real world" (circular and/or geometrically interdependent, etc.) tolerance envelope to Manufacturing that the old "rectangular" system (+-.060, +-.0015, etc) could not. It is complicated, but is very well thought out and extremely effective.
It's a language for communicating the intended design -not for creating the design. Initial incorporation teething problems -mostly due to people simply not admitting that they don't understand GDT -can be at any and all levels of the Engineering/Manufacturing/Inspection chain, and are often never admitted to -even years later -for personal pride reasons, and eventually swept under the rug. For this reason, Management may never find out why something didn't work out -and the official explanation will become simply "something happened" -kind of like in the case of the "Rodbender". That's at least been my experience here in the US -Germany may be different. . . Last edited by clambake; 05-31-2011 at 05:10 PM. Reason: clerical |
#464
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demensioning
All well and good,but, if management implements geometric dimensioning, then they ought to train everyone that will be using it or there will indeed be problems. Around "here" they "forgot" to train ANYONE on second or third shift. "you mean someone works at night?" Five years have past, still no training! Anyone here Fly? I don't! Oh yes they forgot second shift when they implemented SPC too.
Jon J at an aircraft plant in Wichita Ks. on the east side.
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Jon J. 81 240D |
#465
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There you go -Jon provides anecdotal evidence of GDT poorly incorporated -and (I deduce) in a place that makes planes we all trust our lives to. An American company goes for Five years plus using GDT without adequate training -having personally made parts from that particular company's drawings before, that sounds about right.
Seeing what mistakes a large American company is capable of incorporating GDT, could Mercedes Benz produce what looks to be one bad part, figure out it's because of a degree of misunstanding of GDT, call for more thorough training, and then sweep the whole incident under the rug? And honestly -which is the more egregious scenario? Last edited by clambake; 06-03-2011 at 07:42 PM. Reason: clerical |
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