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Flywheels and turbo bearings by Mark(The Miser)UK on 06 Dec, 2005 14:36
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Does anyone have to hand the # of teeth on a Quantum TD flywheel?
I'm plotting out the lobe profile on my Quantum I/P (which was mis-set to 0.93mm) It looks like the I/P piston thrust takes place over about 54 teeth and I just wanted to check that a quadrant of the flywheel was 65/66 or even 67 teeth
Also I was looking at the for sale section and spotted Jakes 360 deg bearings.What a good idea I thought...
And then I thought some more and wondered wether the 270 deg bearings were not already in surplus of lubrication; but because of the high temperatures required; a high flowrate of oil to cool the bearings and Jake is mentioning reduced flow rates. Surely under extreme loading the oil temperature is going to rise to higher levels than would otherwise.
Is the oversized drain pipe also basically an oil cooler? -
#1 by vwmike on 06 Dec, 2005 15:23
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The Quantum has 132 teeth on the flywheel. Turbo bearings don't require much pressure and the larger return helps to lower pressure in the turbo. If pressure were allowed to rise it would screw up the turbo.
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#2 by Mark(The Miser)UK on 06 Dec, 2005 17:18
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Quote from: "vwmike"
The Quantum has 132 teeth on the flywheel. Turbo bearings don't require much pressure and the larger return helps to lower pressure in the turbo. If pressure were allowed to rise it would screw up the turbo.
Hi Mike,
132 teeth sounds reasonable at first; but where did I get my totally inaccurate figure from?
What I have done whilst checking pump setting was:
Set car to TDC on flywheel
Checked cam slot accurately aligned.
Inserted gauge which reads in 0.0005" per division.
Backed off (anticlockwise) until gauge stabilised. Reset to zero.
As soon as gauge started moving I moved crank 1 tooth at a time until the gauge peaked at 0.0865" This I deemed to be the peak of the cam plate for #1 cylinder. This corresponded to midway between 26/27 teeth on flywheel. A further 27 teeth on the camplate seemed to (symetrically) bottom out again. However from the previous peak to next rise is 40 teeth 40 + 26(7) is 67 times 4 is 264(6) AHHHHHH DUUHHHH! I've just realised crank turns twice speed of pump!!! so it is 132 on the flywheel thanks :roll:
I'll still post this, as I will add the list of readings in 'thou' that I took so, people can create the shape of the cam on the injection stroke and where the operating region is. Maybe I'll jpeg a diagram in the future. To convert to mm x by 0.0254
:idea: Interestingly my initial timing for TDC 0.0365 or 0.93mm is almost a flywheel tooth out :idea:
0, 0.25,1,3,6,10,14,
19,24.5,30.5,36.5,42,47.5,52,
57,61.5,66,70,73,76.5,78.5,
81,83,84.5,85.5,86 #86.5# 86
#mid tooth#
Maybe coupling these readings with piston movement around TDC would be interesting for future development work.
:?: Mike are you agreeing with my hint of a possible increased risk f frying/ life shortening with lower flow bearings?? :?: -
#3 by vwmike on 06 Dec, 2005 18:27
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What exactly do you mean by lower flow?
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#4 by fspGTD on 06 Dec, 2005 18:41
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It's a good question about what's going on with heat in the turbo bearings. But consider that usually any oil-coke buildup is found on the turbine end of the shafts, usually first at the turbine seal area. From there the coke can buildup aroud the shaft and the first oil-lubricated bearing it reaches is the turbine end journal bearing. Seems to me that this is the oil lubricated bearing that runs the hottest - so anything we can do to bias the oil to flow through here would help the oil to carry away more heat and reduce the oil coking. Oil flowing through the thrust bearing, on the opposite and obviously cooler end of the turbo (where aluminum components live instead of stainless components), wouldn't carry away as much heat. Also, consider that some dual-ball bearing turbo designs do away with the thrust bearing completely.
IMO, the best thing you can do to avoid oil coke-induced failure, aside from proper oil maintenance and letting the engine idle to cool off after running it hard, is to replace your turbo's turine-end seal every so often to keep it fresh and working well to keep the exhaust gasses out of the bearing housing. What you see on old turbos is worn seals causing carbon buildup at the extreme end of the shaft, which I believe comes from sooty exhaust gas not even from the oil! An effective seal block off this source of carbon soot and heat, which should definitely help with the coking situation.
For some applications, gapless turbine seal upgrades are available which I recommend (in particular, for the 1.6lTD Garrett / AiResearch). A gapless sealing ring gives fewer paths for the pressurized exhaust gasses to get through. -
#5 by Mark(The Miser)UK on 06 Dec, 2005 20:10
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I have to admit I've really not studied the operation of the bearings on the turbos of my Quantums... They just seem to function! What I did notice a few days ago when I found loose manifold nuts (#4 exhaust) was upon exposing the high pressure side of the intake side of the turbo; I couldn't spin the turbo with my fingers (turn yes) and yet upon starting the engine the rotor would spin to invisibility even on idling.:shock:
Running with a boost gauge when driving the turbo behaves 'normally and begins boost somewhere under 2000 rpm and goes up to 8 or 9 psi. So does the turbo need the oil to 'float'? -
#6 by Mark(The Miser)UK on 06 Dec, 2005 20:28
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Quote from: "fspGTD"
...What you see on old turbos is worn seals causing carbon buildup at the extreme end of the shaft, which I believe comes from sooty exhaust gas not even from the oil! An effective seal block off this source of carbon soot and heat, which should definitely help with the coking situation.
For some applications, gapless turbine seal upgrades are available which I recommend (in particular, for the 1.6lTD Garrett / AiResearch). A gapless sealing ring gives fewer paths for the pressurized exhaust gasses to get through.
So
"good nozzles-good spray-good burn-low soot-low buildup-long life"
How about :twisted: 'new' low pressure nozzles for low noise and higher torque... :twisted: