Message-ID: <038c01bfdfbc$3cf99ae0$0464a8c0@station4>
From: "John Barrett" <2thman@olympus.net>
To: "Lancair Mail List" <lancair.list@olsusa.com>
Subject: Oil selection in the EngineAir V8/ EPI PSRU
Date: Mon, 26 Jun 2000 14:37:57 -0700
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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Hi all,

An engineer suggested to a builder that multi-vis oils might be the proper
choice for aircraft engines:

"I studied the design of journal bearings several years ago, and he (Jack
Kane) has all the variables noted. It's interesting that people run high
viscosity oil (50 weight) in engines in high temperature environments to
keep the viscosity up, when in truth, the higher viscosity oil contributes
to higher temperatures thru the bearings and may actually be detrimental. A
lot of the race car guys have started running multi weight oils of lower
viscosity and the the engines seem to last longer."

The Lancair builder had these comments after reading the above observation:

"Maybe we should be running 10-30 synthetic in Jim's engine.  Do you know
what he is using??"

Jack Kane's (builder of EPI PSRU) response:

"bearings are not the only consideration with respect to the
lubrication (and cooling) of an engine. Highly loaded gear-tooth interfaces
have their own set of requirements with respect to film strength
(viscosity-related) and cooling. Piston-to-wall lubrication offers another
set of requirements; Piston-to-writpin another; cam-folloower-to-cam lobe
another; Valve stem-to-valve guide yet another. Often these requirements are
members of an intersecting set, but sometimes there are conflicting
requirements, so a workable compromise must be struck.

What was said about higher viscosity contributing to higher
temperatures is true in the absolute, but in most instances, the magnitude
of
the change is insignificantly small (and often times unmeasurable).

There are lots of popular THEORIES about oil systems. A similar one is the
popular theory that an oil pump which uses a short-circuit bypass-type of
pressure regulator adds heat to the pumped oil. True in the absolute but
insignificant in magnitude, and the proposed (and marketed) "solution"
(dumping the bypassed oil into the pan rather than back into the pump inlet)
is totally unacceptable with respect to the other problems (input sizing,
vortexing, and potential cavitation) that the proposed "solution" creates.

(FYI: Oil pump capacity is determined by the pressure and volume
requirements
at idle speed and max design oil temperature. That causes most pumps to be
vastly over-capacity in the normal operating range, which requires some form
of bypass in order to contain the output pressure to within the design
limits. At operating speed, the traditional automotive pump regulator
short-circuits most of the  pump output   back into the pump inlet, which
dramatically reduces the size of the required inlet plumbing and the
associated cavitation and vortexing problems at the inlet. The "solution" to
this non-problem dumps the bypassed oil directly back to the pan, creating a
very large inlet problem indeed.)

There's a lot of theory around about how to build successful engines, but
until someone has actually built and run SEVERAL high performance engines in
their intended environments with documented success, theories tend to carry
a
limited value. (And not all experience with 2700 RPM Ly-Cons transfers well
to high-RPM V8-based designs.)

Al Joniec (and I) have access to knowledgeable people in the highest levels
of
racing (Winston Cup and IRL), and I know that Al keeps abreast of the latest
experiments and their success and failure rates, so I can assure you that
the
oil Al has selected (and recommends) is an excellent choice for the whole
package."

Phone interview with Jim Rahm reveals this information:

"We use Castrol GTX 20-50 for a fifty hour breakin period, then switch to
Castrol Semi-synthetic 20-50.  We also use Marvel Mystery Oil - 4oz :10 gal
for top end lubrication.  In fact Al says in a turbocharged airplane if you
can't find the MMO at the airport where you just landed for gas - park the
plane and rent a car until you can procure the stuff.  In other words -
don't fly without it in a turbocharged a/c."

Second phone interview with EPI's Jack Kane went something like this:

"I'm pretty sure Al uses 40 weight oil in the EngineAir V8 because I recall
a discussion we had on this subject many months ago - let me call him while
you're on the line and see if things have changed.  It seems Al has seen
some advantages to semi-synthetic oils and feels that with frequent oil
changes, you can avoid the disadvantages.  With regard to the Mobil
synthetic oils and the law suits that followed, 100LL has four times as much
lead as the highest octane autogas ever made.  Full synthetic oils don't
have the ability to dissolve lead salts.  The semi-synthetic multi viscosity
oils allow the best qualities of both worlds to be realized."

***** Although all comments attributed to others are in quotes, the phone
interviews were translated loosely and may contain errors unintentionally
introduced by the editor - me.

Regards,

John Barrett - LIVP
CARBINGE- "The World Hinges on Us"
360 385 1000


[The rotary racing crowd has been mixing oil with their fuel for some time
in order to provide lubrication to the apex seals and eliminate the need
for injecting crankcase oil into the cylinders to do that job.  Needless to
say, the carbon buildup from regularly burning crankcase oil was totally
undesirable, so they went to mixing a different (ie, combustible) oil
with the fuel instead.

Early on the guys were using Marvel Mystery Oil but discovered that it didn't
exactly burn cleanly either.  You can test this yourself by putting some
in a metal container and baking it at 500 degrees for awhile... it winds
up leaving a black gooey mess on the container.  This is the same gooey
mess that would want to line the inside of the combustion chamber, plugs,
valves, etc when mixing this material with your fuel.  Instead of MMO
these folks have switched over to regular 2-stroke engine oil, as it is
an ashless dispersant oil and leaves no residue at all when burnt.  The 
mix ratio being used is 1:128, or 1oz/gallon and the end result is less
carbon buildup with the same if not better lubrication characteristics.

FWIW...     <Marv>         ]
  

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