WTB. crank in good shape.
#31
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The green line is an electrical measurement taken across the two surfaces. 100% means it is completely insulating (and a 100% thick film), and 0% means there is complete electrical conductance across the two surfaces. This is a lab test, which has its own set of caveats, and not all oils have the same characteristics. But I put it up there to show that racing oils are designed to run at elevated temperatures. The higher numbers are better.
Sorry I didn't catch that before I posted it. I've looked at it enough that I forget it needs interpretation.
Sorry I didn't catch that before I posted it. I've looked at it enough that I forget it needs interpretation.
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#32
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I don’t doubt that Greg is right, but how is getting more flow in the crank going to help? (note that I said ‘in the crank’ since it does not increase oil flow anywhere else in the system)
That’s like adding a 4” fire hose on to the end of a garden hose. You are not going to get more oil out of a system that is having a problem upstream.
What actually keeps your rod bearings from failing is the hydrodynamic wedge principle. The pressures at the hydrodynamic wedge are not created by the oil system pressures, in fact the rod bearings will survive with as little as 5 psi (at the bearing). Rather than go off on an engineering discussion of hydrodynamic wedges you can google it or check out http://en.wikipedia.org/wiki/Fluid_bearing
The problems with the 944 oiling system all lie upstream of the rod bearing –
1) 951s run high oil temps – loss of viscosity
2) 951s suffer from oil aeration due to poor oil control in the crankcase
3) All 944 oil pumps will cavatate at higher engine speeds
4) There is a 90 degree corner in the crankshaft oil passage
Put all of those together and you have some problems that cross drilling will not help.
That’s like adding a 4” fire hose on to the end of a garden hose. You are not going to get more oil out of a system that is having a problem upstream.
What actually keeps your rod bearings from failing is the hydrodynamic wedge principle. The pressures at the hydrodynamic wedge are not created by the oil system pressures, in fact the rod bearings will survive with as little as 5 psi (at the bearing). Rather than go off on an engineering discussion of hydrodynamic wedges you can google it or check out http://en.wikipedia.org/wiki/Fluid_bearing
The problems with the 944 oiling system all lie upstream of the rod bearing –
1) 951s run high oil temps – loss of viscosity
2) 951s suffer from oil aeration due to poor oil control in the crankcase
3) All 944 oil pumps will cavatate at higher engine speeds
4) There is a 90 degree corner in the crankshaft oil passage
Put all of those together and you have some problems that cross drilling will not help.
Last edited by KSira; 01-14-2012 at 03:59 AM. Reason: Typo