We often discuss common rail concerns, but I came across this today.
Thought it may be interesting due to the pics of the engine internals.
link
uk-mkivs.net/forums/1/841326/ShowThread.aspx
comments? Is VW moving to common rail as a result of these pumpe duse failures?
Regards
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Almost certainly the wrong oil has been used at sometime, although the 150 PS version of the PD is the "lemon" of the bunch (the 130 is the peach). I don't know why this is - yet.
There are several good reasons why VAG are abandoning their PD system but for most engine variants, given correct treatment (difficult with VAG documentation) durability is not an issue. Cost of manufacture is probably the main reason, coupled with servicability problems relating to the need for special oil and the very highly stressed camshaft drive.
659.
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PD technology makes sense though it is simply daft to drive the pump units off a belt driven camshaft.
CR makes more sense because injection pressure it totally independant of cam timing, it is also more space efficient which is why VAG have gone CR on V config diesels.
The 150 PD system will surely be the same as the 130 though IIRC the turbo is different.
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The worn parts in the pictures are nothing to do with the PD injection system which has a roller follower cam and rocker for each unit injector. The parts you see are the bucket followers for the engine inlet and exhaust valves.
I will check part numbers but I'm fairly sure that the 150 PS unit has different valve timing and possibly higher lift valve cams than the 130. The pictures are consistent with either lubrication failure or a surface treatment problem with the cams or followers.
659.
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Just another case of ARL cam-follower disease - we covered this a couple of weeks ago.
The PD is far simpler and more durable than a CR and I've never seen a VW CR - the diesel V6 has enough problems without that as well.
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VW are moving to CR. They've pretty much taken PD to its maximum. Also the refinement of the PD system is not good enough.
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I agree with Xileno in that the PD is totally outclassed in terms of refinement.
It has been a good work horse although not totally without it's problems but it needs updating to keep up with the competition.
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I think the real reason is cost: it has been possible to add piezzo-electric control of the PD injectors to give multiple shots, but it costs and there are CR improvements in pressure which make PD a luxury. With piezzo however, refinement would be improved, all other things being equal.
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The PD is far simpler and more durable than a CR and I've never seen a VW CR - the diesel V6 has enough problems without that as well.
With respect screwloose, in principal CR is much simpler, one HP as opposed to four (on a 4cyl) unit pumps.
The latest VAG V6's and IIRC V10's are CR, also the LeMans Audi R10 that they place so much disel tech marketing weight upon.
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In practice the PD is elegantly simple - a pre-requisite of reliablity. The HP common-rail is - and will always remain - a pig's breakfast and should have been dropped as totally impractical at conception. Nothing that complex will ever be durable unless built by NASA with an open chequebook.
I've certainly heard that VW are going CR; but I've not had the pleasure of working on their Le Mans car, or any of the new A8 diesels - yet.
Still; a VW-built mass-market CR system should give a nice boost to the pension fund....
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