So long as the thermal paste is kept off of the electrode area. The paste
is electrically conductive as well.
None on the plug body. Once you have it inside a wire sleeve, you cannot
clean it out. Throw that wire away and start over.
Reduce the torque on the plug by about 10% as the paste is a great
lubricant.
Autolite Racing plugs are about $10.00 for 4 plugs. Heat range about the
same as an NGK 10. The gap is difficult to change as the ground
electrode is cut back to expose the end of the center electrode.
Autolite number AR 2592. Most parts stores can have these for
you overnight.
The point of colder heat range plugs is that the car duty cycle is quite
low, or less than 30%, while the aircraft may be close to 100%. You seldom
jump into an RX-7 and drive for an hour at full throttle, but you can do that
in a rotary powered airplane. Even race cars can have lower duty cycles than
airplanes.
Rotaries fire the plugs every revolution of the crank, like a 2 stoke.
Overheated plugs cause lateral cracks to appear through the plug holes in the
chrome.
I found a set of Champion N-57G. Gold Pladium fine wire center electrode.
We ran these years ago. No longer available. Came out of the box gapped
at .012" .
One advantage of the NGKs is the long body. Great if you run a killer
ignition system. Less chance of a stray lightning bolt close to the plugs. CD
and CD multi spark systems put out lethal voltages.
Lynn E. Hanover
In a message dated 9/27/2017 11:42:16 A.M. Eastern Daylight Time,
flyrotary@lancaironline.net writes:
Charlie, this subject has been brought up before but if anyone is
going to answer it you might have to wait 1-2 years for anything definitive
on SAG. I suppose a temperature probe around a spark plug before/after
would determine if better heat transfer occurs. I personally use copper-coat
on my spark plugs as an anti-seize compound.
Jeff
OK, I really
can't remember if I've brought this up. I've thought about posting it, but I
couldn't find any record of doing it. Forgive me if I'm repeating
myself.
On the subject of spark plug SAG, and the great research
Steve Boese did several years ago, it seemed that extreme temps in the plug
itself was what is causing the quick degradation of the plugs. There was
talk about running colder plugs, and IIRC, Lynn mentioned high-dollar racing
plugs as a potential solution.
As I've begun my research into
operating a Rotax 503 2stroke, I discovered that Rotax recommends using heat
sink thermal-transfer paste on the spark plug threads of Rotax engines, to
improve heat transfer out of the plugs. They even quote a temperature drop
number for paste use.
If it works for a Rotax, I've been
wondering if it would help with the rotary, running the coldest
off-the-shelf (affordable) plugs.
Any thoughts? Anyone care to try
it? If you need a little to experiment with, I've got a couple of lifetimes
supply from one of my previous lives, & could send you a
bit.
Charlie
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