WTB. crank in good shape.
#16
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#17
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The way the oil pump is driven makes it pretty much impossible to upgrade it. The only possibility is to use a belt driven external oil pump. That is possible but you will have to give up either power steering or A/C. You will also have to give up a large sum of cash do get that done right!
#18
That depends on a lot of variables. If you are using a light flywheel you don’t want to take too much weight off the crank – you will have stalling problems with a grippy clutch. Turning a crank is not the easiest job – you need to make sure you are removing the same amount of weight for each journal to keep the torsional damping at its best.
The way the oil pump is driven makes it pretty much impossible to upgrade it. The only possibility is to use a belt driven external oil pump. That is possible but you will have to give up either power steering or A/C. You will also have to give up a large sum of cash do get that done right!
The way the oil pump is driven makes it pretty much impossible to upgrade it. The only possibility is to use a belt driven external oil pump. That is possible but you will have to give up either power steering or A/C. You will also have to give up a large sum of cash do get that done right!
#19
Race Car
#20
110 is acceptable. 125 is way to much in may opinion, even with good oil. If you have 125deg on the oil going in to the engine, imagine how hot it will be once inside the engine.
#21
Race Car
Besides, once you are at operating temperature, oil viscosity is pretty stable as you get hotter.
#22
Burning Brakes
Thread Starter
KSira
How wide is your cooler and where is it mounted? I'm about to buy a cooler and I want to be sure it's not too small.
Also, where do you measure the temperature?
I run a massive 60rows oil cooler and still get 110deg C on a "hot" (for Norway) track day.
Also, where do you measure the temperature?
#23
Burning Brakes
Thread Starter
Chris don't you think that the absence of the windage holes you describe here can be a major reason for the bearing failures?
I want to have such ports machined in the block. Even drilling a few holes should help. If I remove the pistons from the block there is no way I can keep the old rings is there?
The block 'floor' is higher than the 2.5 so the free standing cylinders are held in place better. The windage holes are large holes above the crank that allow air to move between cylinders 1&2 and 3&4. Remember that all the air being moved as the piston goes down has to go somewhere, as piston 1 goes down piston 2 is going up so the volume of air has to move through the crank case from cylinder 1 to cylinder 2 – and it has to do that at 200 times per second at 6krpm. That’s a lot of air moving back and forth. In the 2.5 block the air has to pass under the crank and girdle – right by the oil on the oil pan. That’s a lot of air moving around and it will move the oil around too.
The S2 block has the windage holes located so the windage can move back and forth above the crank – away from the oil!
The S2 block has the windage holes located so the windage can move back and forth above the crank – away from the oil!
#24
Race Director
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
#25
Race Director
No direct data to support this. Bearings sping at just about any time. If it were a simple signal point of failure it would have been resolved. The fact that the best "soltions" are band-aids or "Dry sump" tells me the issue goes very deep in the motor design.
#26
Temperatures are usually taken in the sump, which is before it runs through the oil cooler, and after it has been "worked" through the bearings, bores, etc. So we may not be talking apples to apples. But in the sump, 125 (255F) is very common. 135 (275F) is starting to get considered hot, and 150 (300F) is a shut down temperature (and that's usually due to other problems, not with the oil!). Note the oil doesn't flash until 200 (390). This is not specific to 944's, moreso the oil. 115 (240F) is about the lowest I've seen in sump temps on track cars (with gauges I know worked). I do know of one car that indicates lower, but it indicates oil temps below coolant temps with the stock oil cooler, so I don't trust the readings.
Besides, once you are at operating temperature, oil viscosity is pretty stable as you get hotter.
Besides, once you are at operating temperature, oil viscosity is pretty stable as you get hotter.
EDIT: Above 120 deg in the oil pan is no go for me
EDIT2: Just out of curiosity, are there any test available that shows how the oils lubrication ability is effected by increased heat?
Last edited by KSira; 01-12-2012 at 01:24 PM.
#27
It's measured in the oil pan, at the oil drain plug, which is the coldest part with air constantly flowing over it. The cooler itself is mounted about where the stock IC would go.
#28
Race Car
I still think cold oil is a cheap way of ensuring that the engine components does not have to high operating temperature. In my view, as much heat as possible should be removed from the engine and its compartment. So far a blown head gasket that looked like it was the original one from 86 is the only failure (knock on wood)
EDIT: Above 120 deg in the oil pan is no go for me
EDIT2: Just out of curiosity, are there any test available that shows how the oils lubrication ability is effected by increased heat?
EDIT: Above 120 deg in the oil pan is no go for me
EDIT2: Just out of curiosity, are there any test available that shows how the oils lubrication ability is effected by increased heat?
Also, here is an interesting article. I looked the guy up, as when a "Dr." began talking about owning multiple Ferraris and Lambos, I questioned what kind of Dr. that was. MD, not Ph.D. But the guy has done more research here than probably anyone on this thread other than Chris White. Note he addresses some points about flow versus pressure, etc. http://www.minimania.com/web/display...8/ArticleV.cfm I assume when he specifies a "thickness," the actual number is centistrokes (cSt). Note a 10W60's viscosity at 100C is about 22cSt, and a 5W40 is 14 cSt.
#29
As a matter of fact, these kinds of tests are run pretty regularly. This one is of a very well known player in racing oils. Note how poor the film thickness is until the oil gets sufficiently hot. Also notice the coefficient of friction gets lower with more heat.
Also, here is an interesting article. I looked the guy up, as when a "Dr." began talking about owning multiple Ferraris and Lambos, I questioned what kind of Dr. that was. MD, not Ph.D. But the guy has done more research here than probably anyone on this thread other than Chris White. Note he addresses some points about flow versus pressure, etc. http://www.minimania.com/web/display...8/ArticleV.cfm I assume when he specifies a "thickness," the actual number is centistrokes (cSt). Note a 10W60's viscosity at 100C is about 22cSt, and a 5W40 is 14 cSt.
Also, here is an interesting article. I looked the guy up, as when a "Dr." began talking about owning multiple Ferraris and Lambos, I questioned what kind of Dr. that was. MD, not Ph.D. But the guy has done more research here than probably anyone on this thread other than Chris White. Note he addresses some points about flow versus pressure, etc. http://www.minimania.com/web/display...8/ArticleV.cfm I assume when he specifies a "thickness," the actual number is centistrokes (cSt). Note a 10W60's viscosity at 100C is about 22cSt, and a 5W40 is 14 cSt.
#30
Race Car
Sorry I didn't catch that before I posted it. I've looked at it enough that I forget it needs interpretation.