Too bad Lynn I was counting on you for some good data. Omega has a whole
slew
 of products that will work. Some are ceramic coated. To be useful the probe
 needs to be with in 2 mm of the combustion chamber surface right adjacent
 to the leading spark plug. If you are reading this in time and are still
interested
 I can give you some part numbers out of the Omega catalog. I assume these
are  12A rotor housings.

 Paul Lamar

At Curtiss-Wright/Deere/RPI, we always used spring loaded thermocouples to
measure metal temperature. You want to make sure that the thermocouple is in
firm contact with the metal (and it should be down a dry hole, not in the
coolant passage). Any material that gets between the metal and the
thermocouple will insulate it and change the results.

Jon Lauter
Rotary Power Marine Corporation

Good points Jon thanks.

Paul Lamar

I thought that Mazda had a pretty good idea of the wall temps around the plugs. I saw that diagram here. I thought you wanted the coolant temps a few thousandth away from the wall. Was this incorrect?

Lynn E. Hanover.

Here are my suggestions Lynn. 

Use two hole 1/16 OD ceramic insulator TRA 164 116 for $25
for package of five six inches long.

You will need to make a small clamp to go around the ceramic so a small spring
can push it down the hole as Jon mentioned. The clamp can be epoxied on
as the temp will be below 200 F out side of the hole and rotor housing.

Now you need the the wire. Fine Gage type K thermocouples. .015 OD wire.
Wire could then be CHAL-015 page A9 $17 for a package of 5. Good for 700 degrees F.

Type K  gives about 20 millivolts at 1000 degrees F. 
10 millivolts at 500 degrees F. Linear response. 

Now you need connectors and an EGT gage.

The gage used must be matched to the type K.

BTW
I notice that Omega has the response time for this wire size on page A8.
Tracy is always wining about how the response time of thermocouples
are too slow for fuel injection feed back and that is why he does not
want to use EGT as one of his inputs. :-) Well here it is!   For .015 OD
wire it is 800 F to 100 F in 0.8 seconds for 60 ft/per second
air flow. That is 875 degrees per second!!! Type K is good for 
1600 F in this wire size.

Also BTW
Two cycle engines would be far more reliable with an EFI system
that measure the CHT EGT and changed the mixture to cool or heat the 
engine when a piston seize was eminent.

Paul Lamar
 
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