Scientific Data on Engine Operations

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. That's not to
say that I haven't seen a lot that were acceptably smooth - I have.
That's also not to say that I haven't seen engines that ran smoother
LOP with GAMI's than ROP without - I have. But those engines with
GAMI's ran even smoother ROP. When operating LOP, the fuel-air
distribution needs to be much closer to perfect than ROP for the same
level of vibration, simply because the power vs fuel curve is MUCH
steeper. By the same token, unless the distribution is absolutely
perfect (which it never is except maybe at one altitude and power
setting) ROP will always be smoother. I'm sure that at some point the
difference isn't important anymore (the vibration due to power
imbalance is swamped by other factors) but nobody can say with any
authority what that point is.

Of course all the piston airliners routinely ran LOP - but it's
important to remember that over the course of its life, the cost of
fuel the engine burns is significantly higher than the cost of the
overhaul - and thus LOP operation, which can easily save 10-15% for the
same power and speed, can be economically advantageous even if it does
measurably shorten engine life.

Michael

"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

On Fri, 15 Jul 2005 11:27:54 -0700, Michael wrote:

The extra vibration occurs only if you don't have proper fuel
distribution LOP
[snip]

Of course all the piston airliners routinely ran LOP - but it's
important to remember that over the course of its life, the cost of
fuel the engine burns is significantly higher than the cost of the
overhaul - and thus LOP operation, which can easily save 10-15% for the
same power and speed, can be economically advantageous even if it does
measurably shorten engine life.

Michael

This seems like one of the most straight forward and reasonable statements
you've made thus far. That's a good point. A very good point. Have
anything which validates that's the real reason they ran LOP?

"Greg Copeland" wrote in message
news
On Fri, 15 Jul 2005 11:27:54 -0700, Michael wrote:

The extra vibration occurs only if you don't have proper fuel
distribution LOP
[snip]

Of course all the piston airliners routinely ran LOP - but it's
important to remember that over the course of its life, the cost of
fuel the engine burns is significantly higher than the cost of the
overhaul - and thus LOP operation, which can easily save 10-15% for the
same power and speed, can be economically advantageous even if it does
measurably shorten engine life.

Michael

This seems like one of the most straight forward and reasonable statements
you've made thus far. That's a good point. A very good point. Have
anything which validates that's the real reason they ran LOP?

Less fuel, cleaner, better internal pressures...all things that make for
BETTER TBO. Some of the airlines were running their radial engines to
3500-4000 hrs between overhauls.

"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%.
================================================== ================

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

"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.

On Sat, 16 Jul 2005 02:51:27 +0000, bill hunter wrote:

[snip]
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.


I thought LOP was not recommended for turbo applications?

"Greg Copeland" wrote in message
news
On Sat, 16 Jul 2005 02:51:27 +0000, bill hunter wrote:

[snip]
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.


I thought LOP was not recommended for turbo applications?


See Deakin's series, "Those Fire-Breathing Turbo's", parts 1-6.

http://www.avweb.com/news/columns/182146-1.html

"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