On 31 Jan 2005 14:26:32 GMT, (WbSearch) wrote:

Unfortunately one of you statements is contradictory. Polishing the cylinder
walls to a much higher degree lessens the chance of oil to lubricate as it
would be wiped off, not having the minor 'indentations' to adhere to; unless it
is a pressure lubricated interface. A porous metal cannot be polished more
than a less porous metal just by definition. A bearing surface profilameter
test would confirm this, a standard surface finish test would not be appropiate
for this situation.

Wrong. The smoother the bore the less friction, oil or no oil.
There is no such thing as a minor indentation in a cylinder sleeve.
The surface characteristics are on the microscopic level. i.e in the
grain of the steel.
If you really new anything about engine mechanics you'd know about the
oil ring, which holds oil in between itself and the compression rings
for lubrication on the downward stroke.
The simple engine we're talking about use a slinger which has higher
rpm ensuring the cylinder/sleeve is aways being splashed with oil as
well.
As for qualities in the metals used for the sleeves/ friction
surfaces, yes porosity DOES make a difference, as the oil migrates
into the grain of the metal. Especially as it reaches operating
temperatures.
Go back to metalurgy 101 if you're going to try and discuss design
theory in regards to internal combustion engines with me.( I've got
over four decades of experince working on power plants from
jet/turbine engines on down.)

On a similar subject, I know of many automotive engines/transmissions that were
in service far beyond the 12,000 mile warranty. Manufacturing warranty has no
direct correlation to component/subsystem design criteria. It is a marketing
decision. At least it was for the automotive/marine manufacturing companies I
worked with.

Sure, it's all about the Warranty. Which is a business decision, which
in the case of Briggs and Stratton is partially influenced by the fact
that for the past 15 or so years they've been having their motors made
in the Pacific rim and I might add for as little outlay as possible.
Might explain why so many lock up right out the box.