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01-27-2014, 03:15 PM | #1959 | |
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01-27-2014, 03:50 PM | #1960 |
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01-27-2014, 10:48 PM | #1961 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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01-30-2014, 11:33 AM | #1962 |
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Here's a head's up for this thread. The Clevite guys have finished analyzing the bearings. Clevite guys have given me permission to post the results. As soon as I get answers to one or two more question, I will collate the info and post it.
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01-30-2014, 08:55 PM | #1964 |
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Why brother posting that if your not going to tell us what you know? Why wouldn't you post the answers you have? Seems like you enjoy being conytolling
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01-30-2014, 10:37 PM | #1965 |
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I had planned to finish writing it all up. But two things intervened before I could get done. Sorry to disappoint you.
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01-30-2014, 10:42 PM | #1966 |
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01-30-2014, 11:10 PM | #1967 |
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Here's the response from Clevite. Black text will be the response verbatim. Where enecessary, I collated answers from multiple emails together into the same topic. Clevite granted permission to post this in public.
Q: Are there any signs of detonation? A: Probably, but certainly signs of very high cylinder pressure on the supercharged applications. Detonation is uncontrolled combustion of the fuel in an engine. Normal combustion in an engine starts with a fuel burn at the sparkplug then burns on an ever expanding flame front until the fuel is consumed. It is similar to a grass fire starting at one spot and burning in an ever expanding flame front. In detonation the spark ignites the fuel then fuel on the back side of the combustion chamber explodes before the flame front has reached it. When that occurs, cylinder pressure spikes quickly and sometimes reaches 2-3 times normal cylinder pressure. The duration of the spike is short but that pressure spike is really hard on the oil film. Those dark, worn, some what round spots of wear on a number of upper rod bearings may be and probably are indications of that happening. What can cause detonation? Lean fuel conditions, poor octane quality fuel, too much ignition timing, too much engine compression for the fuel being used - these are the most common causes. Q: Do you recall if the signs of detonation were predominantly on supercharged over NA bearings? Or did you see signs on each? A: (Still waiting for the answer to this question.) Q: Are there any signs of bearing clearance deficiencies. The nominal bearing clearance is 0.00140 inch on a 2.04655 inch journal. A: I know you are all hot on this, but I just don't see it. The upper shells in most of the samples show a wear pattern over 2/3 of the surface which we'd consider normal. Q: Are there any signs of oil starvation (might be related to (2) above? A: Lots of indications here. The bearings that show delamination are called a hot-short failure and this is almost always a lack of oil film issue. I think you told me the factory oil recommendation was somewhat thick for the clearance being run. This is also related to oil temp and climate conditions. Q: Is this normal wear given the mileage for each (I will provide mileage for each)? A: I believe these were all non-supercharged applications from the factory, correct? If so, the N/A sets looked pretty normal. Q: How many more miles estimated until break down and failure? A: All the supercharged sets looked pretty poor. Those in the copper were close to total failure. Additional comments: Considerations: It's not my position to second guess BMW engineering. If the cars/engines were all stock that's one thing, but alterations to the OE condition are always made at some risk. We do know that as cylinder pressures increase, oil film thickness decreases. When the thickness reaches what we call boundary lubrication, head builds rapidly and failures result because the shaft and bearing actually start touching. Mixed lubrication, a condition where we move back and forth between boundary and hydrodynamic( seen in many of your samples) results in accelerated wear. Q: Tell me more about #3. BMW-AG only allows 10W60 oil in this engine. BMW-NA seems to have broken ranks with BMW-AG as of August 2013 and now allows 0W30 - 5W40. No other region seems to be allowing thinner oil. Your comments on #3 seem to indicate this is a separate issue than too little clearance on #2. I always thought they were linked and related. Maybe a little clarification on there for my benefit. Tell me more about oil temp and climate conditions as they relate to these samples. A: 1) We know now that the tighter the bearing clearances in engines, the thinner the oil needs to be to flow adequately. We like tight clearances because they; 1) spread the load on the oil film out over a wider area, reducing the psi load on the film and reducing the chances for boundary or mixed lubrication conditions and 2) allow longer engine/bearing life. We also favor full synthetic oil because of it's improved lubrication properties and it's cold weather and hot weather viscosity stability. 2) Bearings that have been hot will typically exhibit wiping or smearing if you will, of the overlay. Next comes discoloration on the bearing material indicating more heat and finally delamination of the bearing material. All three of these conditions were seen in the samples you sent in. The #1 cause of the heat seen in the bearings is loss of oil film thickness resulting in bearing to crankshaft contact. This in turn increases the friction coefficent, resulting in heat. Babbitt overlays melt in the 500F range. Oil is an excellent tool for cooling the engine, but in this case, we have hardly any oil flowing across the surfaces to carry the heat away! Also, please remember, bearings are not self-healing! Damage done during perhaps a cold start or hard pull or a bunch of boost is there for good! 3) Supercharging: I believe, based upon the samples you sent me, that supercharging increases cylinder pressure and consequently, the load upon the conrod, the bearing and ultimately the oil film between the bearing and the crank. We've known, since the day the first engine had a power adder installed, that there was a detriment to the life of the engine as the power is increased. It's pretty much a direct but inverse relationship. More power= less life. I have customers making 10,000 HP in a 490 CID engine but bearing life is less than 1 minute at full throttle/ max boost. 4) We're a bearing manufacturer, suppling both OEM parts and performance parts to the automotive industry. In the performance/ racing venue, we can optimize both materials and designs with just one thing in mind; surviving high power output. We offer a line of performance/race bearings in the aftermarket but not for the BMW engines you have. We also have the capability of manufacturing bearings for companies with very specific needs and applications. As I mentioned, we are quoting on a BMW bearing now for a performance engine builder/supplier specializing in BMW. |
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01-30-2014, 11:19 PM | #1968 | |
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01-30-2014, 11:22 PM | #1969 | |
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01-30-2014, 11:54 PM | #1970 |
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The question is, does the thinner oil help or hurt?
If the cause is high load on the oil film between the bearing and crank, would we not want 10W-60? On the other hand, if the problem is flow through tight clearances then not. |
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01-31-2014, 12:01 AM | #1971 |
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01-31-2014, 01:17 AM | #1972 |
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Hopefully Kawasaki can chime in on this one. It's my understanding from what the Clevite guy says that the thinner oil certainly will help here.
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01-31-2014, 01:53 AM | #1973 |
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4 key observations for me, more or less repeating what they've said but also adding a bit of context:
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01-31-2014, 02:23 AM | #1974 |
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Thanks RG for posting this and also to Clevite for their time as well.
I am pleased to see that detonation gets a mention - after getting relatively little traction and some derision I did lose confidence that it was a factor. As for the 70 pages of text - for me this has been one of the most interesting topics I've been involved with for a long time....well worth the read. Last edited by SenorFunkyPants; 01-31-2014 at 03:01 AM.. |
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01-31-2014, 06:13 AM | #1975 | |
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Since your statement was directed at me, the NA motor that was looked at by myself and our guys did not show the detonation. Some of the SC engines I am sure probably do, havent looked at them so your blanket first statement is false. He said "probably", that means they really cant tell on the NA stuff. The amount of bearings they see that turn 8500 are very slim, this is really a low power high speed engine, not something they ever look at. They are playing both sides of the fence with the clearance issue. When a senior rep who we have worked with for 20 years was in the shop (I have stated this before) he said that clearance is not that big of deal because other cars have been running it for years like honda and toyota. But they run 0-20 and that is how they get away with it. They also do not make the level of power we make therefore it does not work for us. We cant run 0-20 with 450hp on a tuned/exhaust motor that turns 8500. THe oil film is not thick enough, therefore we need to run thicker oil to turn the rpm, that in turn make sthe clearance greater because of the thicker oil. So what they are saying is true about the tight clearance but not for the s65 IMHO. On the flip side if the clearance was .0025 the tws would probably work just fine and we wouldnt be talking about these issues. The fundemental was always there, it was never missing. We all knew what they are gaining but there is a line of what are we getting vs what are we giving up. What we gave up is huge because the pictures of failures and bearings that are beat out just keep piling up. There are many cars that have 100k on them but there are many that have failed and or had the bearings changed just in time before they failed that would have never made it to 100k. Not just he m3 but the m5 also. Ask yourself this.... When we bought the car they told us up front before the paperwork was signed that many cars would not make it to 100k miles without blowing the bottom end out would you still have bought it? I dont lease cars, I like to purchase cars and sell them later. I am going to keep my car and replace bearings but this experience has really made me look at leasing my next car, BMW or not.
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01-31-2014, 06:30 AM | #1976 | |
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Doesn't the build up of carbon round the edge of the piston suggest that the fuel air mix in that area is igniting before the flame front reaches it (from the center)? |
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01-31-2014, 06:40 AM | #1977 | ||
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Running the thinner oil will pump much faster and will fill the clearance void much faster also. I have also stated this before, one revolution of the crank should displace the entire clearance void of oil with fresh oil, take that thin layer of oil all around the crank and everytime it turns over the old should be pushed out and refilled with fresh. That obviously is not happening soon enough that is why the wiping is happening very slowly but sure enough everytime the car starts there is I dont know one maybe 2 or 3 revolutions where it goes through the residual layer and slightly wipes the bearing before the pumped oil gets there. This is why the engines are running as long as they are, it is happening very slowly and very small amount of it is happening at a time. If a engine could be started when new and never shut off, just change the oil on the fly and keep gas in it they would run for a million miles. We all know that is not the real world though. I am rambling but I hope it all makes sense
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01-31-2014, 06:50 AM | #1978 | |
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Hence its possible that an oil like 0W40 Mobil 1 with its large HTHS rating (compared to other similar rated oils) could actually present a "better" oil film condition under given circumstances since it will be running significantly cooler to begin with and it likely experiences less strain rate thinning (since it is designed with a smaller rating range hence less need for VI polymers that produce that strain rate dependent viscosity behavior, i.e. non-Newtonian fluid behavior). Whether any of the above is the case, is a wild-ass-guess from my standpoint; however, others here have *much* more experience and knowledge than me and have provided what are likely excellent recommendations. An aside -- I was listening to that recent Steve Dinan interview yesterday, and he made the comment that over the past 35 years he's been modifying BMW engines that a good rule of thumb is 25%. If you want an engine to last 100k miles with the mods you're doing to it, 25% above factory power is a good stopping point. It seems like a reasonable reply. Of course most all people supercharging an S65 have a much different measurement system for what they consider "reliable."
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01-31-2014, 06:52 AM | #1979 | |
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Something else I wish I could have accomplished and I didnt have a block and pour plate with me and maybe RG could do it is repour the cylinder with these highly carboned pistons and see how much it raises compression. A few of the pistons had enough build up to effectively raise the piston height by about .002, this adds another tenth or two to the overall compression ratio and compounds the problem. Furthermore I shoud have taken a side picture of that because it is hard to see how high the carbon was built up from the top view. There was alot for sure.
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01-31-2014, 07:50 AM | #1980 | |
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My experience at VW/Audi was that the "importer" has very limited technical resources over and above that needed to support the dealer network - the majority of their time is spent on marketing, liaising with dealers etc....and I can see no reason why BMW NA would be any different. Its highly unlikely that BMW NA could unilaterally decided to change the recommended oil for the S65 against the recommendation set out by BMW AG as they are most surely legally bound to basically do as they are told. And even if they were permitted to make their own recommendations they would not have had the technical resources required to R&D this significant change in the first place. Note that I strongly suspect that BMWs contract with Castrol does not allow then to recommend any oil other than Castrol (or BMW rebranded Castrol oil) so by extension BMW NA would not be able to recommend generic LL-01 oils sold by any manufacturer other than Castrol. So that leaves us with few options: 1/ BMW AG authorized BMW NA to allow the option to use Castrol 5W-30 alongside the 10W-60 but left it out of the recent Dec 2013 list of approved oils. Not impossible I suppose....there is the whole ll-04 for Europe and LL-01 for the USA marlarkey. 2/ Its an admin cock up. My money is still on 2/ though. Last edited by SenorFunkyPants; 01-31-2014 at 09:49 AM.. |
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