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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