BoatBanter.com - View Single Post

On 14 Jul 2003 10:23:33 -0700, (basskisser) wrote:

"Joe" wrote in message . ..
This from someone who has convinced himself (and Joe) that consume and
burn mean the same thing!!!!! By the way, my neighbor and I had a good
laugh at you and Joe last evening. He's a Chrysler certified mechanic,
so I've shown him your posts. As we were working on his Honda
lawnmower motor, I told him I thought it was the carb acting up, and
he said "Nah, probably not burning enough oil."!

Birds of a feather.

Don't you find it a little curious that NO ONE has agreed with your
position?

Funny, but aircraft machinists do!:

Pleas point out anywhere in your quote below that states an engine
should burn NO oil. You won't be able to, because it doesn't say it.
In fact, the part I snipped below:

In addition to
sealing combustion gases in the combustion chamber, piston rings must
also manage the amount of oil present on the cylinder walls for
lubrication. If the rings do not seat properly, they cannot perform
this function and will allow excessive amounts of oil to accumulate on
the cylinder wall surfaces. This oil is burned each and every time the
cylinder fires. The burning of this oil, coupled with "blow-by"
induced engine breathing, are reasons that an engine that hasn't been
broken in will consume more than its share of oil.

Is in total agreement with everything I've said, and disagrees with
everything you've said.

Keep trying. And next time, don't bring your daughter in to help you,
you pathetic loser.

Steve

Suggestions for Proper Engine Break-In

--------------------------------------------------------------------------------

Whenever an engine's piston rings are replaced whether in part or in
entirety it is necessary to break in the engine. Piston rings are
replaced at a complete engine overhaul or repair, top overhaul or
single cylinder overhaul or repair.

When we refer to engine or cylinder break in, we are talking about the
physical mating of the engine's piston rings to it's corresponding
cylinder wall. That is, we want to physically wear the new piston
rings into the cylinder wall until a compatible seal between the two
is achieved.

Proper engine break in will produce an engine that achieves maximum
power output with the least amount of oil consumption due to the fact
that the piston rings have seated properly to the cylinder wall. When
the piston rings are broken in or seated, they do not allow combustion
gases to escape the combustion chamber past the piston rings into the
crankcase section of the engine. This lack of "blow-by" keeps your
engine running cleaner and cooler by preventing hot combustion gases
and by-products from entering the crankcase section of the engine.
Excessive "blow-by" will cause the crankcase section of the engine to
become pressurized and contaminated with combustion gases, which in
turn will force normal oil vapors out of the engine's breather,
causing the engine to consume excessive amounts of oil. In addition to
sealing combustion gases in the combustion chamber, piston rings must
also manage the amount of oil present on the cylinder walls for
lubrication. If the rings do not seat properly, they cannot perform
this function and will allow excessive amounts of oil to accumulate on
the cylinder wall surfaces. This oil is burned each and every time the
cylinder fires. The burning of this oil, coupled with "blow-by"
induced engine breathing, are reasons that an engine that hasn't been
broken in will consume more than its share of oil.

When a cylinder is overhauled or repaired the surface of it's walls
are honed with abrasive stones to produce a rough surface that will
help wear the piston rings in. This roughing up of the surface is
known as "cross-hatching". A cylinder wall that has been properly
"cross hatched" has a series of minute peaks and valleys cut into its
surface. The face or portion of the piston ring that interfaces with
the cross hatched cylinder wall is tapered to allow only a small
portion of the ring to contact the honed cylinder wall. When the
engine is operated, the tapered portion of the face of the piston ring
rubs against the coarse surface of the cylinder wall causing wear on
both objects. At the point where the top of the peaks produced by the
honing operation become smooth and the tapered portion of the piston
ring wears flat break in has occurred.

When the engine is operating, a force known as Break Mean Effective
Pressure or B.M.E.P is generated within the combustion chamber.
B.M.E.P. is the resultant force produced from the controlled burning
of the fuel air mixture that the engine runs on. The higher the power
setting the engine is running at, the higher the B.M.E.P. is and
conversely as the power setting is lowered the B.M.E.P. becomes less.

B.M.E.P is an important part of the break in process. When the engine
is running, B.M.E.P. is present in the cylinder behind the piston
rings and it's force pushes the piston ring outward against the coarse
honed cylinder wall. The higher the B.M.E.P, the harder the piston
ring is pushed against the wall. The surface temperature at the piston
ring face and cylinder wall interface will be greater with high
B.M.E.P. than with low B.M.E.P. This is because we are pushing the
ring harder against the rough cylinder wall surface causing high
amounts of friction and thus heat. The primary deterrent of break in
is this heat. Allowing to much heat to build up at the ring to
cylinder wall interface will cause the lubricating oil that is present
to break down and glaze the cylinder wall surface. This glaze will
prevent any further seating of the piston rings. If glazing is allowed
to happen break in will never occur. We must achieve a happy medium
where we are pushing on the ring hard enough to wear it in but not
hard enough to generate enough heat to cause glazing. If glazing
should occur, the only remedy is to remove the effected cylinder,
re-hone it and replace the piston rings and start the whole process
over again.

Understanding what happens in the engine during break in allows us to
comprehend the ideas behind how we should operate the engine after
piston rings have been changed. The normal prescribed flight procedure
after ring replacement is to keep ground running to a minimum, take
off at full power and reduce to climb power at the first available
safe altitude, all while keeping the climb angle flat and the climb
airspeed higher to promote the best cooling possible. At cruise
altitude we should use 65% to 75% power and run the engine richer then
normal. At all times we are to remember that heat is the greatest
enemy of engine break in, we should try to maintain all engine
temperatures in the green, well away from the top of the green arc or
red line. This means step climbing the aircraft if necessary,
operating with the cowl flaps open or in trail position during cruise
flight and being generous with the fuel allocation for the engine. We
should not run the engine above 75% power in cruise flight because the
B.M.E.P is too great and the likelihood of glazing increases. As you
can see, keeping the engine as cool as is practical and at a conducive
power setting is the best combination for successful engine break in.