Scientific Data on Engine Operations

"Michael" wrote in message
oups.com...
The extra vibration occurs only if you don't have proper fuel
distribution LOP

I have never seen an engine, GAMI equipped or otherwise, that was as
smooth LOP as it was ROP - and I've seen a lot of them.

I'll give you a ride in mine.

Not only as smooth, but temps, pressures, carbon deposits, etc. are all MUCH
better.


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

You have to consider the smaller operating range when running LOP. Small
changes in altitude, temperature, or pressure will wider fluctuations in
temperature when running LOP as opposed to ROP. We would all like to think
we keep the engine perfectly leaned, but over the 2000 hours on a typical
engine, how many times does the average pilot let the temperature drift a
little before catching it. How long at 25 or 15 LOP before you shorten the
engine life.
I change altitudes a lot, and tend to fly high when weather permits. I also
have a turbo arrow with a very sensitive throttle that needs to be adjusted
continuously during climbs and decent. I don't need the aggravation of
having to adjust the mixture 3 times as much because I was LOP. I know
during the 2000 hours I would eventually get distracted in busy airspace,
and end up running too close to peek during a cruise climb.

"Michael" wrote in message
oups.com...
So much depends on quality information about proper engine
operations, yet there appears to be little science behind the assertions.

You are quite correct - there is very little science here. There is
certainly a lack of solid statistical evidence. In this situation, you
pretty much have to work from engineering first principles.

Let's start from what is scientifically defensible:

Operating 50 degrees LOP vs 50 degrees ROP (which is what many
manufacturers recommend) means that:
The engine runs slightly rougher. Extra vibration.
The peak pressures in the cylinder (and thus transmitted to the
crankshaft) are lower. Less stress on crankshaft, bearings, etc.

That's about it. Everything else is rumor, conjecture, and guesswork.

The slightly rougher running may in the end reduce the life of the
engine more - or less - than the higher peak pressures in the
cylinders.

Oops, I guess we're done until an actual controlled study shows us
which factor is more important.

Michael

"O. Sami Saydjari" wrote in message
...
Yes, exactly. -Sami

Doug wrote:

I have often thought that what is needed is a scientific study of what
works best in aircraft engines. Get a statistically signifigant number
of engines. Rebuild them. Put monitoring equipment in the aircraft.
Instruct each owner of the aircraft to run the engine in specific ways.
Numerous groups of engines being run different ways. Oil selection, oil
change frequency, leaness, shock cooling etc could all be studied.
After 2000 hours of running one would have a pretty good idea of cause
and effect.

Between the known physics of combustion, the test stand that GAMI has been
operating for several years, the engineering data the P&W and the airlines
generated for a couple decades of operating the radials...I don't think
these folks really want scientific data.

"bill hunter" wrote in message
...
You have to consider the smaller operating range when running LOP. Small
changes in altitude, temperature, or pressure will wider fluctuations in
temperature when running LOP as opposed to ROP. We would all like to think
we keep the engine perfectly leaned, but over the 2000 hours on a typical
engine, how many times does the average pilot let the temperature drift a
little before catching it. How long at 25 or 15 LOP before you shorten the
engine life.

Well, I hope you've kept adequate re$erve$ for a top overhaul in addition to
your early MOH.

"O. Sami Saydjari" wrote in message
...
This is actually a split off from the "Rotating Injectors Among
Cylinders" thread. I prefer not to distract that thread any.

I must say that I find the evidence presented in support on LOP to be
uncompelling.


The exiting data is not only compelling, it's pretty much overwhelming.

Although it is certainly appealing at the gut level, it
is a far cry from scientific evidence that LOP operations is better for
the engine and will lead to longer TBOs.

You need to learn to integrate information.

But why would anyone want to kick in a load of $$$ when Old Wives Tales are
so "compelling". Not only is there no known data to support these OWT's, by
the time people finally quit sitting on their brains and assimilate the new
learning, we'll probably be using mico-nuclear engines.

From geocentric, flat earth, and a host of other "knowledge bases", I guess
ROP/LOP is just another notch in human nature.

I suspect what's wanted here is not scientifc data, but excuses.


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

"Paul kgyy" wrote in message
oups.com...
The extra vibration occurs only if you don't have proper fuel
distribution LOP. Admittedly, this is normal for carburetion and
common for fuel injection, but that's the point of using GAMI injectors.


http://www.avweb.com/news/reviews/182558-1.html
-----------------------


These subjective reports were confirmed recently when Chadwick-Helmuth spent
several days running tests on a 1993 Beech F33A instrumented with one of
C-H's latest state-of-the-art vibration analyzers hooked to multiple
accelerometers and vibration transducers. Tests were flown at a wide range
of power settings and mixtures using a set of standard TCM nozzles, then
repeated after GAMIjectors were installed. The results indicated that the
GAMIjectors reduced vibration levels at the 2nd order frequency and at the
low 1/3rd order frequency by 60% to 80%.
================================================== ================

The exiting data is not only compelling, it's pretty much overwhelming.

I'm glad you feel that way. Those of us who are actually qualified
practicing engineers do not concur.

Michael

"Michael" wrote in message
ups.com...
The exiting data is not only compelling, it's pretty much overwhelming.

I'm glad you feel that way. Those of us who are actually qualified
practicing engineers do not concur.


In what field of engineering?

"Michael" wrote in message
ups.com...
The exiting data is not only compelling, it's pretty much overwhelming.

I'm glad you feel that way. Those of us who are actually qualified
practicing engineers do not concur.


Why?

Be specific and technical.


--
Matt

Why? Be specific and technical.

Where is your long-term field study comparing LOP and ROP operations?
How many engines have been monitored in service from start to overhaul,
under what conditions, and for how long? Have you shown a
statistically significant difference in MTBF, service life, or cost of
maintenance? That's really the only way to cover all bases. Sometimes
this is not practical, but lacking a long term field study, you at
least need a reasonable model. A compelling model would address the
following issues, as a minimum:

What are your parameters to asess engine roughness in normal LOP and
ROP operations? How do you model the imperfections caused by pilot
technique? Do you have amplitude and frequency data on engine
vibration at various mixture settings? What kind of sensors did you
use?

Do you have long term operational data or at least a model showing the
long term behaviour of the engine mounts, bearings, cases, crankshaft,
etc. under the vibration conditions? Without long-term operational
data, I would expect at least an FEA.

Do you have any information at all on the differences in combustion
end-products in excess-air vs. excess-fuel combustion reactions? I can
assure you they are differrent. Are any of the combustion products
harmful to the engine components long-term? Do any pose corrosion
issues when the aircraft is not flown for several days or weeks, as
commonly happens with private planes?

How about that big mixture pull - it takes the mixture through peak.
What is the effect of this transition on the crankshaft? Some analysis
of this issue was done in the 1940's, using the limited available tools
- but only for radial engines, which have significantly different
crankshaft designs. For that matter, about the only large base of
operational data in the LOP regime comes from radial engines - which
are different - using 1940's and 1950's fuels which were significantly
different than what you're burning now.

I'm sure given time I could think of other issues.

The main arguments for LOP operation are short-term economic ones -
less plug fouling, lower fuel burn. These are pretty compelling. As
for effect on TBO and general engine longevity, there has been much
hype and no compelling evidence.

BTW - to answer your other question - I run the R&D group for a major
manufacturer of industrial instrumentation. So yes, this is pretty
much right up my alley.

Michael