|
|
<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
<< Lancair Builders' Mail List >>
<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
Carl, please allow me to interject some comments on your last post?
My Understanding: In extensive discussions with Orin and the folks at
TCM, LOP operation should only be used when operating the TSIO-550-E at
or below 65% power.<<
Who, precisely, at TCM told you this? Was he an engineer? Or a salesman?
Or a customer service rep? I think I have heard reports of about 10
different recommendations out of TCM on this subject.
Has that person or anybody else at TCM ever personally operated one of these
engines at high power and lean of peak for extended periods of time? I
have. Continuously at 265+ cruise Hp and 60 to 90F lean of peak, for very
long periods of time and then torn the engine down and measured all of the
critical cylinder components, which, after 800 hours, remained essentially
within ... NOT service limits, but NEW limits. But much more important than a "he said" - "somebody else said" type
discussion, is the issue of what the data shows. Ask TCM if they have any
data to support that claim. Here is what the data shows. At .75 X 350 Hp and operating the engine 50
to 125F rich of peak, the peak internal cylinder pressures will be 10 to 15%
higher than the same engine operated at the same 0.75x350Hp with the engine
leaned and operating 60 to 90F LOP. AND, operating ROP, the CHTs will be
about 30-40F hotter than when LOP at the same horsepower. I have a 100
dollar bill for anybody that can show me any data that is materially
inconsistent with what I just wrote. I have another 100 dollar bill for
anybody that comes up with any data, or even any legitimate engineering
analysis as to why operating the engine with high peak cylinder pressures
and higher CHTs is "better" for the engine than otherwise.
In order to get the peak cylinder pressures and CHTs down to the same level
as those observed with 60 to 90F LOP, one has to operate the engine VERY
ROP. Like 250 to 350F ROP.
To do it at higher power settings is going to significantly shorten the
life of the engine.<<
With all due respect, where is the data? How can the engine life get much
shorter than it already is (typically 400 to 700 TOH) when these engines are
operated at 75% power and rich of peak ?
If you are going to run at higher power settings, the fuel flow needs to
be set to yield
readings of 50-75 degrees ROP. The greatest danger zone is 50 degrees
ROP to peak.<<
Well... the greatest danger zone is actually around 35F ROP. But anywhere
from about 25F LOP out to about 150 to 200F ROP ought to be considered
"forbidden territory" for any of these engines operating at .75X350Hp.
Leaner than 25F LOP or richer than about 150 to 200F ROP will be much better
for the engine than anywhere in the "forbidden territory".
It is my conclusion from reading and discussing this with the GAMI
folks, that they claim there is no shortening of the life of the engine
to run the engine at higher power settings lean of peak as long as you
are using their injectors. TCM does not agree and TCM has to warranty
the early cylinder failures. <<
It is not an issue of our injectors and the life extension. The only issue
with the injectors is to get the engine to: 1) operate smoothly lean of
peak;and 2) to keep all of the six EGTs a reasonably uniform number of
degrees away from peak on the lean side (or the rich side if you want to run
it rich).
Engines will probably last longer at 65% LOP than they will at 75% LOP. But the available accumulated experience is pretty clear that engines
operating at 75% and 75F LOP will last a hell of a lot longer than the same
engine operating at the same HP and 75F ROP.
Performing the power vs. temperature curve on the E model in my plane
shows very little variance in the peak temperatures across the
cylinders. So in my opinion, very little would be gained in using GAMI
injectors.<<
I don't know what that means. But, the lean test described and downloadable
from the GAMI web site is the ONLY test I know of that will give you any
meaningful information as to the variation from one cylinder to the next,
about the fuel air ratio of your cylinders. The absolute value of the
temperatures is almost useless in this regard.
The right question to ask is, while leaning the engine from rich to lean of
peak: What is the fuel flow when the first cylinder peaks and what is the
fuel flow when the last cylinder hits its peak EGT? If that number, on a
top down induction engine is not less than about 0.4 gph, then it can be
made enough better to be noticed and make an operational difference by
fixing the F/A ratios.
So currently I am running 75 degrees lean of peak at cruise. I am using
2400 rpm and 29" manifold pressure. I burn 15.5 gph.<<
Conservative as my grandmother, but nothing wrong with that, which will
figure to about 212 Hp or about 61% of 350 rated power.
My TIT is typically 1510-1540. The hottest cylinder is #5 at 310. I
adjust the oil door to keep the oil at 170.<<
Those are all reasonable and extremely conservative numbers. I would allow
the oil temp to get above 190 to 200F at least briefly during the late part
of the climb in each flight to make sure the water is boiled off.
In climb, I use full rich, 30" and 2500 rpm and see 1200-1400 fpm.
Hottest cylinder #5 is 370-380<<
I would probably use 32 or 33" and 2700 RPM during the climb, and a TIT that
was sufficiently rich to keep the hottest CHT at or below 380F. Once you
find that "magic" TIT then it becomes a very useful reference or "target"
TIT and can be relied on for a quick reference during the climb.
And it runs very smoothly, even smoother now with my MT prop dynamically
balanced. I also add 4 oz. of Marvel's Mystery Oil per 10 gallons.
I make certain my oil temperature is 30 degrees or warmer before any
start. My disclaimer: I am just a guy out in the sticks of Eastern Washington
still trying to figure out life and having fun.<< Sounds like you are doing pretty good.
LML website: http://members.olsusa.com/mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please remember that purchases from the Builders' Bookstore
assist with the management of the LML.
Please send your photos and drawings to marvkaye@olsusa.com.
|
|