Kieth--a little more on squeeze films. Picture here a loose fit pin and rod
bearing combination. The clearance between the pin and rod is filled with
oil. At 6000 rpm the time between the start of compression to the end of
power is 10 milliseconds and maybe 3 or 4 milliseconds under highest loads.
During that time the pin pushes on the oil film at the bottom of the rod
bushing and the oil flows both around the bearing to the looser upper side.
Some small amount is pushed out the side of the bearing. During this time
the clearance on the top of the bearing is opening up and receiving some oil
from the squeezed bottom side of the bushing and the rest to fill the void
is pushed in from outside by atmospheric pressure (15psi). Now reduce the
atmospheric pressure and the oil doesn't completely fill the void because
there is less force behind it to push it into the void. The higher the
speed the worse the situation assuming BMEP (and torque) remain the same
because there is less time to get that bearing clearance filled. Vacuum in
the crankcase means less pressure to force replenishing oil into the pin
bushing clearance. I think the tipoff here is when you begin to see
distress in the pin to bushing (or pin to piston in the case of press-fitted
pins) contact surfaces. Note also there is likely an effect here due to oil
viscosity. Can't tell you exactly whether heavier or lighter viscosity oil
is better in this situation.
Ed Weldon
----- Original Message -----
From: "Keith Turk" <kturk@ala.net>
To: "Ed Weldon" <23.weldon@comcast.net>; <Askotto@aol.com>;
<land-speed@autox.team.net>
Sent: Thursday, October 19, 2006 10:36 PM
Subject: Re: Dry sump oiling HP gains, the truth.
> Could be why these Carillo rods that I have are emp drilled from the crank
> to the wrist pin eh? hmmm......... K
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