Brian said,
> "Not sure on VW, but according to both Lycoming and Continental below
65%
power you can run as rich or lean as you want without danger of hurting
the engine, just need to pay attention to the CHT and make sure they are
in limits (which running LOP actually lowers the CHT)."
I treat the GP2180 just like I would any carburated aircraft engine.
With Steve's manifold pipes and the Ellison, fuel distribution is about
as good as having GAMI's - my assessment from what I found when taking
the heads off at around 500 hours after the Rimco valve spring failures.
My colors were a uniform light tan. I use 70% as the border between what
I can and cannot do with the mixture, but since none of this is precise
without very good engine instrumentation (which I don't have) 65% is a
safer ballpark figure.
Persistently running rich will clog up the guides and quickly build up
black gook in the combustion chambers that causes pre-ignition,
detonation, raises CHT's and wastes money, reduces range - all sorts of
unwanted consequences.
That Deakin article I linked to is way too convoluted and boggy with
charts and distracting information which makes a time consuming process
of finding the essential points. The information is there, it's just
almost hopeless to get to the nut of it quickly. I would hope those
unfamiliar with Pelican's Perch use that article as a starting point and
go through his many other articles on engine operation.
It was through Deakin's writing that I learned you can't trust even fresh
factory Lycomings and Continentals to have valves perfectly concentric
with the seats. Some do, some don't. Some series of engines were
notorious for this problem and others weren't. Those with problems from
the factory have early valve failures which gets blamed on the operator.
This is the same thing that happened with Jim Hill's GP engine. The
lesson I've taken from all this is that we need to take things apart and
make sure things were done right to start with. That, or buy the engine
as a kit and build it yourself. Those two Revmaster R-2300's we've read
about are "perhaps" good examples of this very point. I don't know
enough about either situation to say. I do know Joe Horvath would not
put something on the market with inherent design flaws. He's been around
too long and his company's reputation is on the line. Clearly with those
two engines we've read about there was something out of whack. They
either were not put together well at the shop or they were overheated in
operation for extended periods. It's not hard (with consistent improper
operation) to ruin an air-cooled engine no matter how well it's put
together.
As for having a "professional" do your valve work, Steve used to use
Rimco to re-build his heads. Rimco in LA set the standard at one time
for VW shops - yet with my heads they did what can only be called
butchery in cutting the seats and then saved themselves a few pennies by
re-using old valve springs - springs which were crappy quality to start
with. Yet those heads went 500 hours even with this kind of
"professional" treatment. These are simple engines and with all the
resources available, especially Langford's documentation of engine work
that has become well-known around the world (literally), there's no
reason to ever turn our precious engines over to "professionals".
Mike
KSEE
.
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