Perry ,
Aren't you using direct drive? Vaughn.-
Yes.
Perry Mick
Duckt N7XR
Perry,
I have so many questions to try to help you resolve this problem but I'll
try to keep it as short as possible.
Either I missed some of this information already so forgive me if I ask for
info already given.
What type of fouling are you seeing?
Carbon?
Oil?
Lead?
Bridged (by excessive carbon or oil)?
Extreme gap? (doubtful cause of so few hours).
We loose about 0.001 or (0.025mm) for every 40 to 60 hrs of flight time.
So that's pretty much a moot point too.
Or none and they are pretty normal looking light tan and or gray deposits?
Next, have you tested the resistance of the wiring itself with an ohmmeter?
I really doubt this as the problem because they act pretty much OK after you
clean the plugs, right? But a high amount of resistance can cause them to
foul up sooner than they should.
If you want to test each wire from one end to the other, you should see not
over 25,000 ohms. 30,000 is considered a little too high and you should
replace them all at that point.
I personally hate the amount of lead in 100LL. If I remember right it's
about 2ppm per gallon (mostly used for detonation purposes and four times
what the old grade 80 had in it) now and that is way to much (because of
adverse contamination) even for most dinosaur aircraft engines.
We have to keep the oil changed on a vigilant basis because that's where it
ends up in a very large amount which in turn loads up the exhaust valve
guides on many LYC's. and some Continentals.
Here is a quote from a leading dinosaur manufacture, service letter L192 :
"The problem of lead fouling arises when low engine operating temperatures
coupled with a rich mixture prevent the complete vaporization of the TEL
(tetraethyl lead). Under these conditions, lead deposits can form in the
spark plug electrodes, causing misfiring. By establishing and maintaining
proper engine operating temperatures, the TEL can be kept properly vaporized
and pass out the exhaust system.
But if you don't see it on your plug and especially down in the bottoms
where the porcelain meets the metal then I'd say that's not it either but it
may be a contributor..
It sounds like a chain of events that may be have progressed to where now it
is becoming a real nuisance.
Have you considered you're using direct drive and this lower RPM is a
contributing factor to lower Thermal Dynamics, As an example 100LL
contains other scavenging agents that help break up and burn the TEL, but
they require specific higher temperatures that your engine may not be
developing because of the inherent direct drive in your case (lower RPM may
equal lower thermal dynamics and a richer mixture = less scavenging, higher
deposits all the way around).
BTW, have checked your timing lately and also your compression? These would
also be contributors (bad apex seal, low compression or late timing).
If you remove and replace all of the fuel with fresh Mo-gas, be sure and
change the oil and filter and clean or replace the plugs, fly it again to
see if this problem comes back, but you cannot use any 100LL till after the
test.
Then of course you'll at least know where you stand and maybe have some idea
of how to deal with the problem in the future.
After all, it's pretty darn hard to fly any sort of a cross country without
getting forced to by 100LL.
When you know for sure if it is the lead that started these symptoms then
you'll be better armed on how to deal with it in the future. There is even
an additive for leaded fuel that help to break it down (makes it softer too)
it's called TCP concentrate by Alcor. I just checked and Aircraft Spruce
sells it for 19.95 a quart.
http://www.aircraftspruce.com/catmain.php?dest=cathome.html Many people
swear by it! Go here and click on search then put in "TCP". It goes a long
ways..Half that cost if you buy a gallon.
PS, remember, indicated water temp does not accurately reflect combustion
temps, how's the exhaust temps?
I know how frustrating this can be, I have had my share and then some.
Vaughn Mann in east TN.
Thanks for the info Vaughn. It's really not a problem most of the
time. My local flying I always burn mogas. I'll just go back to
hotter plugs on leading. May try the TCP next time I travel, if
I can't find a fuel stop with mogas/80.
I don't think it's temperature related due to lower direct-drive
RPM, as my temps actually run rather high. Cruising at 5200 RPM
oil temp will still be 200 even when it's cool ambient. I'm not sure
why, but I know I couldn't run 6500 if I had a redrive, because
my oil temp would be way over redline.
--
Perry Mick
Duckt N7XR
http://www.ductedfan.com
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