Douglas Fir wrote:
HI Paul,
I got to fly in the SeaWind finally. Great experience and a very stable
craft. I must be the only builder of a SeaWind who had a demo ride 4 years
after he purchased the kit.
Of course I noted some data on airspeeds and fuel burn to get an idea of
range and more importantly the HP required. Here is a link to a commentary
that all will enjoy. The author disputes the advice Lycoming is given about
running LOP.
http://www.avweb.com/news/columns/182131-1.html
My rebuild kit should arrive in June so I can get busy on the engine. I'm
presently working on an original designed landing gear.
Doug in Japan
Your Lycoming warrantee is void if you run LOP.
BTW Doug, if you see a cute Mazda RX8 TV add in Japan could you capture the video.
I would like to add it to my collection on my new web site below,
Paul Lamar
David Staten wrote:
Would you mind providing the documentation that backs up that claim of warranty denial? How would they KNOW if you ran rich (or lean) of peak? Especially if from a scientificly proven standpoint
that Rich of Peak is actually hotter/harder on the engine?
Dave
I don't have it. It was told to me by a Lycoming rep at Reno.
Of course they would not know if it was something other than a burned
exhaust valve or melted cylinder head.
By definition "peak EGT" is the hottest EGT. How can anything be hotter than the hottest?
This is not opinion. This is fact.
Rich of peak EGT cools the engine and lean of peak EGT cools the engine as well.
There is no doubt what so ever that the hottest EGT is harder on the exhaust valves
and the aluminum cylinder heads. This too is fact and not opinion.
Paul Lamar
David Staten wrote:
The chart you have affixed to this thread showing EGT, CHT, power and BSFC CLEARLY shows that the cylinder head temps are hottest (peak CHT) at a temperature that is NOT the same as peak EGT. Even
more noteworthy is the fact that this higher CHT occurs Rich of Peak. The chart that you attached validates my assertion that running rich of peak EGT actually causes a hotter engine condition (in
the approx 50 deg F range ROP) as measured by the CHT's. It is excessively high CHT's that will shorten engine life. Considering that ROP EGT is clearly hotter and more problematic (with regards to
CHT's), I again wonder how Lycoming is going to claim "heat damage" from LOP operation.
Dave
Granted.
None of that makes much difference if you descend and forget to lean the mixture.
In that case the valve temp increases 100 F and will stay well over maximum
red line for a wide range in altitudes before finally dropping down below
redline. If you start at rich of peak and go down from there by descending the valve
temp and cylinder head temp will always be lower than redline no matter
what the pilot does. That is the way Lycoming wants you to fly the engine.
I have always maintained that an EGT based computer control algorithm is what
is needed in aircraft engines. That will extend the life in real world conditions
with the average pilot as opposed to the theoretical ideal world with
a perfect pilot.
Fortunately the rotary is not so high strung and picky about EGT.
We don't give a damn. We can run the rotary engine at any EGT that gives
best power or best BSFC and not worry about forgetting to change the mixture
with altitude. Tracy's computer has a manual mixture control so
you can lean to best BSFC at cruise altitude.
Scenario: Pilot forgets to change the mixture.
Start Operation. Power ...... Fuel Air...... Mixture .. EGT
---------------------------------------------------------------
LOP ..climb .... Reducing ....Same decreasing leaner lower
LOP ..descend .. Increasing ..Same increasing richer higher
ROP ..climb .... Reducing ....Same decreasing leaner maybe the same due to reduced power.
ROP ..descend .. increasing ..Same increasing Richer lower
The combination of increased power with richer mixture and higher EGT
while descending is the valve killer while operating lean of peak.
Paul Lamar
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