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I agree that the "idea" auto spark plug for the flying rotary is still waiting in the wings. I am currently using a special lead scavenging formula to see if it can extend the useful life of lead fouled spark plugs (don't ask I don't know what's in it {:>)). Well, see whether it does anything for the problem.
I normally get approx 25 hours on a set before SAG sets in using 100LL. I speculate that one reason that such things as TCP do not appear to do much for the rotary engine is that the chemical reaction apparently (according to reports) requires the high cylinder head temperatures of air cooled cylinders (like 375F +). I believe that with our plugs buried within the housing (as opposed to protruding into the combustion chamber (and they had better not or you will clip your apex seals), that the plugs do not reach a sufficiently high temperature to deter fouling or to activate the TCP chemical reaction. So perhaps a "hotter" plug might help - on the other hand, since we are running WOT for longer periods that many rotary racers - I'm not certain I want a hotter plug.
I have tried fine wire and the stock plugs - but both seemed to have the same problem of lead fouling the ceramic cone and "bleeding" off spark causing misfiring.
My $0.02
Ed
----- Original Message ----- From: "John Overman" <mooneydryver@yahoo.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, November 18, 2006 10:39 PM
Subject: [FlyRotary] Re: Spark Plugs
The most troublesome aspect of rotary engines in
airplanes has to be the spark plugs. Everyone uses the
BUR7 of BUR9 or the finewire plugs. When you look at
the business end of these plugs your first thought has
to be this is a fouled plug waiting to happen. Even
when not using Avgas fliers like Tracy are only
getting 200 hours on them. With Avgas they last like
25 hours.
These plugs may work ok in a car with a generally
lighter load but they seem ill advised for aircraft.
There a lot of "standard" design spark plugs with the
same thread diameter and thread depth out there. I
wounder has anyone tried a more standard type of plug
to see how they may hold up?
John Overman
Velocity N711VE (reserved)
--- Dennis Haverlah <clouduster@austin.rr.com> wrote:
Thanks everyone for the spark plug cleaning
recommendations. I tried
brake cleaner and oven cleaner. The oven cleaner
appeared to work much
better. I had been running the fine wire RE7A L and
RE9B T plugs that
came with my Renesis. After cleaning they still had
s slight miss at
full throttle. I cleaned an old set of plugs that
came with a 1987
engine BUR7EQ L and BUR9EQ T and tried them. The
engine ran better and
had no miss at full throttle. I believe these are
the same plugs Tracy
has been running in his Renesis. All the plugs are
manufactured by NGK.
Dennis H.
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