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On 17 Jul 2003 11:06:03 -0700, (basskisser) wrote:

(Steven Shelikoff) wrote in message
Again, I ask a simple question. If the rings, on a properly broken in
engine seal well enough to keep molecularly small exhaust gases from
getting INTO the crankcase, at a pressure of approx. 100 p.s.i., how
in the HELL does something molecularly larger (oil) make it through
the same rings at a third of the pressure? How?

Because the pressure of the oil against the rings as they are moving
down the cylinder wall is many times greater than 100 psi. And because
oil molecules tend to stick together in a thin film. That's one of the
properties that makes oil a good lubricant. What will really blow your
mind when you think of it is that oil can get past the rings on the
power stroke, where the pressure in the cylinder is much greater than
100 psi. However, the pressure against the rings from the top is
nowhere near as high as the pressure in the cylinder due to the tight
clearance between the piston and the cylinder. If the rings had to face
the full pressure of the combustion gasses in the cylinder (as the would
if there was a lot of space between the piston and cylinder) they could
never do their job of keeping combustion gasses out of the crankcase.
As it is, they only have to seal against the small amount of gasses that
make it between the piston and the cylinder.

Steve

Okay, here we go. You are now claiming that the pressure in the
crankcase, at the time that a piston is moving down the cylinder, is
"many times greater than 100 p.s.i.????? Are you just plain flipping
NUTS? Let's say it's an eight cylinder motor, okay? Using YOUR
analogy, then, with eight cylinders, there is almost always a cylinder
moving "down". SO, just how many times 100 psi should my oil pressure
gauge show? Should it be 500 psi? 600psi? Now, because it is
essentially ONE vessel ie: the crankcase, there can not be a
differential in pressure, so don't even try it. That would be akin to
saying that the pressure is different in one side of an air compressor
tank than it is in the other side. NOT.

Somehow, I knew you wouldn't get it. Well, I know I shouldn't do this
because proving you wrong has just gotten to be a dangerous exercise.
But I'll leave you with a few thoughts:

First, do you think your oil pressure gauge is reading the pressure of
the oil against the rings as they are moving rapidly down the cylinder
wall? or do you think it is reading the pressure at the oil pressure
gauge sensor? Do you think the pressure the oil is under is constant
everywhere in the engine? i.e., do you think it's under the same
pressure when it's between the crankshaft and the rod with the rod
pushing down on the crankshaft as it is dripping down from head back
into the crankcase?

And second, we'll take your hypothetical air compressor tank and attach
a hose to the tank that's only, say, 0.05 inches ID and 100 feet long
with the far end about 5% open to simulate the efficiency of a set of
rings. Say there is 100 psi against the walls of the tank feeding the
hose. How much pressure do you think there will be against the
restrictor at the far end of that long, tiny hose? Remember, the tank
and all the hose really is one big continuous vessel. Do you really
think the pressure is constant against the walls everywhere in that
vessel? Do you really think the 95% restrictor is seeing the same 100
psi against it at the end of 100 feet of 0.05" hose as it would be
seeing if it were right at the outlet of the tank? I HOPE you say no.

Hell, an even simpler case: You have 2 garden hoses, both 100 feet long
and both with the same type of sprinkler head on each. One hose is 1"
think and the other is 0.001" think. Turn on the valve and let the same
water pressure into the hoses. Which one do you think will have more
pressure at the sprinkler when you open the sprinkler? Or do you think
both sprinklers will have the same pressure behind them?

Now, there is the EXACT same amount of pressure of the gasses on the
rings, in pounds per square inch, as there is on the top of the
piston. VERY simple physics.

Maybe TOO simple physics. Yes, definitely TOO simple physics. You're
thinking in the static case when the situation we're talking about is
dynamic. I realize that's probably too much of a stretch for you.

Now that I've proven you wrong yet again, are you gonna come after me
and hunt me down?

Steve