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
Matt Prather wrote:
Hi Paul,
How are you doing these days??
I think John Deakin and George Braly demonstrate that the operating
mixture that Lycoming recommends (25-75 deg ROP) is hotter for the engine
than a 100deg LOP operating point which is possible on many properly
injected Lyc or Cont. If the mixture distribution in a Lyc or Cont is
good enough that all of the cyls reach Peak EGT at the same mixture
setting, operating LOP is a very viable alternative. Just don't run it
within that hottest window, beit ROP or LOP (like you said).
Regards,
Matt-
VE N34RD, C150 N714BK
I am doing fine. Thanks for asking.
I think that is quite possible. I also think what Lycoming has in mind is
if you are at cruising altitude and you are leaned 100 degrees LOP when
you descend and forget to richen the mixture the engine will go to peak
EGT and burn the valves or ruin the head. One must always think out of the
box and take every possible scenario into consideration. We as engineers
still screw up because there is always someone out there that will do
something you never expected them to do knowing what you know. In other
words the correct operations you take for granted.
If it is always on the rich side it will just get richer when you descend.
All you need do is screw up once and you are out a couple of thousand
dollars the next time the annual comes around more than making up for
the few gallons you saved by running LOP.
Fortunately we don't have to worry about that. The rotary does not care
what the mixture is because it has no exhaust valves and the rotor housing
won't melt unless you are running an electric water pump :)
BTW I was flying with a group of people in C172s around Australia. The so-called
leader (Lang Kidby I think) of the group was buying the gas. He ragged me
all the time about burning more gas than everyone else. I was aware of Lycoming cautions
and I do forget to check the mixture when I descend every now and then. I was running
rich of peak. I would rather not have the engine drop a valve over the outback.
That probably makes me a bad pilot. Well I got even with him. I made
an unscheduled stop and put 10 gallons extra in the tank on my own nickel
without telling him. You should have seen his face the next time he filled
up the C172 I was flying :)
Paul Lamar
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