The spark plug washer probes are not inaccurate. You will always
read a higher temperature at the sparkplug than at the screw in probe
location because the temperature is really higher at the sparkplug
location. The sparkplug mount will also respond faster since there is
less mass of metal from there to the fire to slow the response.

If you don't believe this take any brand of thermocouple meter and
make two thermocouples out of the SAME length of thermocouple grade
wire and mount the thermocouples at both locations then measure the
result.
You will also find that the "piggy back" mount where you already have
a screw in heater or a factory CHT probe at the probe hole mount you
will read several degrees lower. It is basic physics 101.

I have a EI scanner and I would not buy another one since the EI
scanner I have requires a UNGROUNDED thermocouple probe. I have to
replace an EGT probe every year or two since oil wicks into the probe
and forms a conductive carbon path to ground. This will cause the EGT
reading on that cylinder to read higher than it should. This can be
verified with an ohm meter.

EI may have changed the design since I bought mine but DO NOT buy a
scanner that requires UNGROUNDED probes or you too will be replacing
probes every year or so because no matter what they say about how well
sealed they are the probes will wick oil and ground out.
John

On 26 Dec 2004 13:31:52 GMT, ospam (Rosspilot)
wrote:


I will not consider any JPI product because of their despicable behaviour to
EI
some years ago.


I'm unaware of this. What did they do?

I just got another report from a friend who has the JPI but said it comes with
cheap (and innacurate) washer-type probes that fit between the plugs and
cylinder heads . . . said the better probes are the screw-in types that go in
the pre-drilled holes on the head . . . recommended Tanis probes. Said once he
put those in, the JPI was perfect.



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