27-09-2012, 11:57 AM | #1 |
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Camshaft Wear
Hi,
The Cam wear I believe is an inherent design fault related to the way the S54 Head retains, or in this case does not, Oil in and around the Cam Bridges and Cam Journals. Most Cam Wear is caused by the lack of Oil retained in the Cam Bridges and Journals upon engine first start up after standing for a period just like Crank bearings etc. The damage is done in the first few seconds from cold start. I do not think the S54 suffers from any form of oil feed or pressure issue to the camshafts as I believe the issue is caused by lack of oil retention, when the engine is switched off and cools down. Go drive a S54 really hard, get it nice and hot then let it idle for about a minute or so to disspearse heat sink and switch off. Leave for a few hours to stand and cool down, then take the oil filler cap off and look inside the cam cover. See how dry the Inlet Cam is around its Journals and around the Cam bridges etc. You would expect to see far more oil retained. When changing out some S54 Cams a while back it was surprising how little oil there was in and around the the Inlet cam bridges and what little oil was left in the Journals when the Cams were removed. 10-60 synth oil does give a good coating to the Cam lobes, Journals and bridges, but the lack of oil retention is not what I would expect to see on a high performance head. The Cosworth 16v heads or the BMW S14 Heads retain quite a lot of oil in and around the cam bridges and journals, even if the engine has stood for a while. If you run your finger over a Cam lobe there is oil deposited on your finger, not so on the S54 Cams in the same circumstances. Merc 16v and bmw S14 both Twin Cam heads with slant towards the Exhaust cam meaning the Inlet Cam, sits higher. So same design as the S54, Merc is shim under with buckets but for the sake of this discussion does not make any difference. I run the Merc 16v engine of 15-50 syth oil and the cams and cam bridges etc are always well covered in oil when cold, no matter how hard and hot the engine has got previously. I do not believe this issue is mileage related but more to do with the amount of times the engine is stop / started from where a running engine has cooled down and is then started. Just my thoughts. Regards, The Gorilla. |
27-09-2012, 05:00 PM | #2 |
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Interesting......so are you suggesting a change in oil grade perhaps?
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27-09-2012, 07:36 PM | #3 |
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is it worse if the car stands for long periods before startiig like weeks and could you add a cup full before start up?
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27-09-2012, 08:17 PM | #4 | ||
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Quote:
Quote:
Gorilla is correct, but that is just one side to it. That will NOT be the only cause of cam wear. Incorrect shimming, lack of shimming, sticking to the long oil change intervals even though the car is hammered on a regular basis on track. Det can cause cam wear too. Running in period not adhered to Running in rev limits not adhered to Poor metallurgy Blocked exhaust, Caviatation of oil under high rpm high G cornering. These can all have an effect too |
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27-09-2012, 08:28 PM | #5 |
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sticking to the long oil change intervals even though the car is hammered on a regular basis on track.
^^^^ personally i think this is one of the biggest factors. since owning mine its had two additional oil changes between each bmw stated service. and tbo i don't think thats over kill. bmw charge just over the £130 mark for oil and filter only. small price to pay for peace of mind. i am anal with mine tho, as in the trade and have a lot of mechanical sympathy |
28-09-2012, 12:20 AM | #6 |
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My car has done 92k and the cams have shown no sign of wear at all.......but having a complete new engine at 75k miles probably helped
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29-09-2012, 11:54 AM | #7 |
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Hi,
10-60 Syth oil is very good and does do a tremendous job at many temps. The problem with say a Heavier oil is that start up wear increases, and a Lighter Oil may not protect so good at the higher temps. The 'finger'' design does not assist with oil retention on start up, and like Lawsy said there are other factors. Its almost like if you could park the Car at 20 deg so that oil was retained in the head as opposed to it draining away. Sort of almost too efficient design. Motul do a 20-60 fully syth which a colleague runs in his S54 engine, but its not a daily driver, so not really a good guide, but it does appear to leave a heavier 'film' on the cam lobes than 10-60. Regards, The Gorilla. |
29-09-2012, 12:54 PM | #8 |
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Do you mean 20deg sideways of front to back?
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29-09-2012, 01:50 PM | #9 |
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This is a heavy thread and could get a lot heavier, when you start on the 'Liquid Engineering' aspects of an oils viscosity and performance under load/use.
As has been already said camshaft ware can be the result on many contributing factors, but in this instance I think we are considering premature ware which could be avoided, therefore the ability of the cams to maintain sufficient lubricant is paramount, particularly on start-up, whether it be a CSL or a Fiesta, 20-60 might well be the way to go - but who's going to tell the Boffins. Last edited by Neil M; 29-09-2012 at 01:52 PM. |
29-09-2012, 03:11 PM | #10 |
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Hi Shimmy,
Its side to side, ie]as you look at a RHD Car the exhaust header side is raised, so that the engine is siting level across, rather than canted down on the exhaust side. Would just help the oil to ''pool'' as opposed drain away. You then benefit from oil splash etc on start up. Start an S54 from cold and the Oil feeds to the Cams etc are not instantaneous, and even when the Oil light goes out the oil feed to the cams is still not fully pressurised. As Neil M has stated, Oil Viscosity under load and varying Temps is a strange world. Lot of people presume that if you have got a really Good Oil Pressure then your fine, which is not always correct. Much better to have an average Oil Pressure and really good flow, than a really high oil pressure and lower flow. I also think that the Paper elements in the Oil Filtres add to the S54 problem in that when they become ''polluted'' with oil, they restrict flow which increases oil pressure at the sensor point on the S54 but means that less flow is reaching its destinations [Cam/Shells etc]. This becomes critical at high load / high revs in that oil pressure light will not flicker as pressure at the sensor point is good, but flow has been restricted via the polluted filtre to the point where the 'film' of oil that the Cams and Bearings ride on is being rotated out faster than its flowing in. I think changing the Oil filtre more frequently is better than frequent oil changes. On the S54 in the E30 M3 which is Dry sumped, you can not run a paper element filtre with a dry sump system, so its a S/S 75 micron mesh filtre. The oil pressure at say 4500 rpm is around 2.7-3.0 Bar but oil flow, ie] the flow and return to the oil tank is exteremley good. Thus windage in the Crankcase aside, lots of oil must be flowing into and out of the bearings/ cams etc for the scavanges on the pump to pump it. The Oil pressure on the CSL at 4500 rpm is around 4.0-4.5 bar but it runs paper element type filtre on the std Semi Dry sump set up. The interesting thing though, is the oil oversupply feed from the head back to the sump, on the Dry Sump engine always flows a lot more oil than the std Car, which runs with a higher oil pressure as measured at the same pressure point. This is what makes me believe that changing the std Oil Filtre much more frequently may also assist. Regards, The Gorilla. |
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