Perry Mick wrote:

I guess I was lucky on my return flight from Copperstate,
in that the fouling was just starting and the plugs quickly
recovered.  After I got back home it got much worse.
I still had about 20 gallons of evil gas in my tanks when
I got home.  The first couple short flights the fouling was
worse, it would not clear up.  So I took the plugs out and
cleaned them, added 10 gallons of mogas to the remaining
10 gallons of 100LL.  It was fine again until today.  Plugs
were once again fouled after operating a couple hours on
50% mogas/50% avgas. Would not clear.  Now I've
added more mogas, probably down to a 25% avgas mixture,
and I'm going to have to take the plugs out again and clean
them once more.

I'm using BUR9EQP trailing platinum plugs in all four
locations.  I think this makes the fouling worse since
the 9 is a colder plug.

--
Perry Mick
Duckt N7XR
http://www.ductedfan.com

Thanks for the report, Perry.

    You may correct about 4 BUR9EQP plugs contributing to your

fouling

problem.  I use the BUR7 and BUR9 and get approx 20-30 hours of

flying

before the plugs start to foul on the 100LL.  The old SAG (Sparkplug
Attention Getter) will put your heart to pumping faster.  I've never

had

the

engine indicate it was going to quit- but there is a power loss, the

EGT

drops 200-300 DegF and the rpm drops approx 200-400 depending if one

or

both

chambers have fouled plugs.  At least that is my experience, but it

can

certainly appear to be a fuel problem when you first encounter it.

Ed Anderson

Save some of those fouled spark plug guys and send them to me.
Aden is sending an MSD ignition system to me and I can experiment
a bit with the plugs on the dyno.

Paul Lamar

Ok, Paul, I have no shortage of used/fouled plugs.

Ed Anderson

I am seriously thinking about getting some PC boards made up
for a fast "plasma" MSD system. Should I put a cheap PIC on
the PC board for ultimately timing flexibility?

Tracy and I were talking about FET failure modes at Shady Bend.
He said he had one short so I will have to fuse
each FET individually otherwise a short could take down
all three FETs.

Paul Lamar

I would think one of the low to med level PIC chips (cheap but capable)
would do the job. although for the small difference in price the 18XX series
with EEPROM/Flash memory might be better.  What type of inputs? Rpm,
Manifold Pressure?, temp? combustion chamber pressure? knock sensor?

Ed Anderson

Just the timing between CD pulses. The basic engine spark timing would come from
Tracy's EFI/IGN system. Knock sensor input might be a good idea as
I don't think Tracy has any plans to provide that. Am I wrong Tracy?

The timing between CD pulses could be done with just a few TTL gates.
No PIC necessary. I just thought I would use one in case we thought
of a real need in the future.

Paul Lamar
 
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