Turbo Oil Feed
22 November 2000, 01:51 PM
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Right, following on from my ramblings on Stef's 'Help!!!!' Thread....
If the oil gallery for main bearing no 3 is shared with the feed for the turbo has blocking the turbo feed from there and moving it to somewhere else been tried?
Pat and I were discussing this idea and thought that it might be possible to take a separate feed to the turbo and use an electric pump to move the oil around.
John Felstead mentioned cooling the oil...maybe we were talking cross purposes, but I was thinking of using the engine oil supply with a resovior to help control pressure/surge, not an independent Turbo oiling system...although...
So thoughts please
If the oil gallery for main bearing no 3 is shared with the feed for the turbo has blocking the turbo feed from there and moving it to somewhere else been tried?
Pat and I were discussing this idea and thought that it might be possible to take a separate feed to the turbo and use an electric pump to move the oil around.
John Felstead mentioned cooling the oil...maybe we were talking cross purposes, but I was thinking of using the engine oil supply with a resovior to help control pressure/surge, not an independent Turbo oiling system...although...
So thoughts please
22 November 2000, 11:28 PM
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Tim W,
I have never stripped or rebuilt a Subaru engine, but your description of how the number 3 bearing, mains or big end, (on crossflow fords the mains bearing gets the initial feed from the gallery in the block, then the big end from a drilling in the crank, I would have assumed Subarus were the same).
Either way if the turbo bearings were begining to fail, as Stef has said his turbo was damaged, and presumably allowing a greater volume of oil to flow past them, thereby reducing back pressure on that branch of the oil feed, surely that would be the most likely cause of insufficient oil feed to the main bearing, which then fails also.
The oil will take the line of least resistance, and flood post any bearing surface that has too great a clearance, in this case the failing turbo bearings.
If this scenario sounds plausible, then would it not be possible to fit some kind of restrictor in the turbo oil feed, to control the amount of back pressure within that branch, to protect the main bearing in the event of turbo meltdown.
I appreciate the very idea of putting any kind of restrictor, which would potentially increase the chance of an oil feed becoming totally blocked, within an oil feed line as probably not ideal, but!!!
I have never stripped or rebuilt a turbo either, but the principles of oil delivery around an engine, should be pretty much the same, or I may well be talking out of my hat, it wouldn't be the first time.
The idea of an electrical pump controlling oil feed to any part of the engine would worry me, as if any kind of electrical malfunction was to occuur, than no oil feed and wrecked turbo. When the oil is pumped mechanically, the pump would 'normally' only stop when the engine stops, at which time oil feed is no longer required anyway.
Cheers MTR
I have never stripped or rebuilt a Subaru engine, but your description of how the number 3 bearing, mains or big end, (on crossflow fords the mains bearing gets the initial feed from the gallery in the block, then the big end from a drilling in the crank, I would have assumed Subarus were the same).
Either way if the turbo bearings were begining to fail, as Stef has said his turbo was damaged, and presumably allowing a greater volume of oil to flow past them, thereby reducing back pressure on that branch of the oil feed, surely that would be the most likely cause of insufficient oil feed to the main bearing, which then fails also.
The oil will take the line of least resistance, and flood post any bearing surface that has too great a clearance, in this case the failing turbo bearings.
If this scenario sounds plausible, then would it not be possible to fit some kind of restrictor in the turbo oil feed, to control the amount of back pressure within that branch, to protect the main bearing in the event of turbo meltdown.
I appreciate the very idea of putting any kind of restrictor, which would potentially increase the chance of an oil feed becoming totally blocked, within an oil feed line as probably not ideal, but!!!
I have never stripped or rebuilt a turbo either, but the principles of oil delivery around an engine, should be pretty much the same, or I may well be talking out of my hat, it wouldn't be the first time.
The idea of an electrical pump controlling oil feed to any part of the engine would worry me, as if any kind of electrical malfunction was to occuur, than no oil feed and wrecked turbo. When the oil is pumped mechanically, the pump would 'normally' only stop when the engine stops, at which time oil feed is no longer required anyway.
Cheers MTR
23 November 2000, 01:30 PM
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As I've mentiined in my other thread, my new engine will be going away to have a direct oil feed to no.3 bearing fitted.
This should be as good if not better than a direct feed to the turbo should it not?
Stef.
This should be as good if not better than a direct feed to the turbo should it not?
Stef.
23 November 2000, 03:40 PM
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Tim might have hit on something - you can get some cute little 1 & 2-row oil coolers from Goodridge, plumbing one of those into the oil feed line to the turbo (& installing at one end of the intercooler OR in front of the rads)could be a possibility.
This assumes there is a separate external oil-line to the turbo to plumb into, of course! Also assumes that available oil-line bores will balance the flow to turbo & crank correctly. (Not that far-fetched - presumably the existing line is a standard size) I know nothing if it's got 4 wheels....
Though I would agree with jfelstead's point on changing oil & filter after a trackday...
But is the design REALLY that cr4p that 2 major components operating at different rates, loadings, and temperatures (never mind a mix of plain and roller bearings) share the same oil feed branch?
Coat and flamesuit ready.....
This assumes there is a separate external oil-line to the turbo to plumb into, of course! Also assumes that available oil-line bores will balance the flow to turbo & crank correctly. (Not that far-fetched - presumably the existing line is a standard size) I know nothing if it's got 4 wheels....
Though I would agree with jfelstead's point on changing oil & filter after a trackday...
But is the design REALLY that cr4p that 2 major components operating at different rates, loadings, and temperatures (never mind a mix of plain and roller bearings) share the same oil feed branch?
Coat and flamesuit ready.....
23 November 2000, 11:09 PM
#5
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The oil feed in question feeds both number two and three big ends, so why did no 2 not fail when that is the leanest cylinder ? Turbo oil feed is not affected by bearing failure as they are not sleeve bearings and the cross section available to flow will not change that much.
Stef, you had a high pressure oil switch fitted I think, assume that this did not light up ? Oil pressure in the region of 6 bar should more than cope with turbo bearing problems. More likely oil film breakdown causing pickup momentarily, once that happens then its only a matter of time.
Stef, you had a high pressure oil switch fitted I think, assume that this did not light up ? Oil pressure in the region of 6 bar should more than cope with turbo bearing problems. More likely oil film breakdown causing pickup momentarily, once that happens then its only a matter of time.
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