Crank oil clearance oil pressure Q...
05-22-2008, 10:58 PM
#1
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Crank oil clearance oil pressure Q...
Ok, bear with me...
The oil clearance between the crank main and rod bearing is filled with oil.. Upon combustion, what kind of pressures are created in this space?? The easy answer is, Depending on the RPM, But I don't think it's JUST regular oil pressure.... ie: 55lbs..
The oil clearance between the crank main and rod bearing is filled with oil.. Upon combustion, what kind of pressures are created in this space?? The easy answer is, Depending on the RPM, But I don't think it's JUST regular oil pressure.... ie: 55lbs..
05-23-2008, 02:54 AM
#2
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You'll hurt yourself trying to calculate this 
.
You have to get into a couple different types of viscocity etc etc to figure out what happens. Theres several things going on, theres a volumetric flow of oil coming in at a given temp, theres heat transfer coming off the journals and bearings. There is a shearing force from the journal and the bearing on the oil, and then theres the outgoing volumetric flow. And on and on and on.....
When you get down to it if you want to know what kind of pressures there are, you'll have to figure out where on the journal at what rpm at what hp level, and at what crank angle so you can guess on the side loading of the piston based on geometry. and on and on and on again.
All the testing I have ever been involved with using any simple sort of calculation was wildly inaccurate. In fact I'm fairly certain the CE guys end up using super computers and making estimates of viscocity effects using super computers to model individual molecules of the fluid. They arent working on car engines when they do that though afaik.
All you need to know is that liquids are for the most part incompressible, or we deal with them that way. Its the perfect way to transfer a load from the crank to the mains without any metal on metal contact.
Your assumption is right though, its not just 55lbs, thats just a pressure that happens between the size of your leaks vs the volume pumped.
.You have to get into a couple different types of viscocity etc etc to figure out what happens. Theres several things going on, theres a volumetric flow of oil coming in at a given temp, theres heat transfer coming off the journals and bearings. There is a shearing force from the journal and the bearing on the oil, and then theres the outgoing volumetric flow. And on and on and on.....
When you get down to it if you want to know what kind of pressures there are, you'll have to figure out where on the journal at what rpm at what hp level, and at what crank angle so you can guess on the side loading of the piston based on geometry. and on and on and on again.
All the testing I have ever been involved with using any simple sort of calculation was wildly inaccurate. In fact I'm fairly certain the CE guys end up using super computers and making estimates of viscocity effects using super computers to model individual molecules of the fluid. They arent working on car engines when they do that though afaik.
All you need to know is that liquids are for the most part incompressible, or we deal with them that way. Its the perfect way to transfer a load from the crank to the mains without any metal on metal contact.
Your assumption is right though, its not just 55lbs, thats just a pressure that happens between the size of your leaks vs the volume pumped.
05-23-2008, 05:07 PM
#3
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Yeah, I suppose it's a lot to concider.. Pressure is built an an orifice. (sp?) ... From the pump, to where ever the oil flows first.. I know #7 cyls lifter gets oil first, but that's the valve train side of the house.. Pressure would be built as soon as the oil enters the crank journal passages... But then again, that's just operating oil pressure.
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