You will find that power will not change drasticly when changing fuel (unless you are way off) but when you start playing with timing you will see big changes.

 

Ted,
All those thermocouplers are K type ungrounded sensors and don't react as fast as a grounded thermocoupler. Unfortunately if they were grounded it would give us a screwed up reading if the actual probe itself or sheilding touched a metal intake pipe or some other part of the body. Ungrounded basically means the junction where the two wires are joined is not in contact with the inner part of the probe, hence it won't heat up as fast as if it was in contact with the probe (grounded). I found out the hard way by buying a grounded probe unknowingly and I tested it out before installing in car it worked perfect but after installing the darn thing was giving me erroneous readings. That's because the probe was in contact with the compression fitting which was in contact with the exhaust pipe. After researching this in a catalog I found out that I needed the ungrounded probe. All those Greddy, Apexi, and other name bands are ungrounded and way over priced. I get my probes, K type and J type, ungrounded, from Plastic Process Equipment for less than $20. Yes, they are that cheap and the thermocoupler wires are in a metal sheath as well. Only thing I had to do was get and modify a compression fitting and brazed it on my pipe. Since we're in the plastic business, at my work, we buy numerous sensors and what not. I'm concerned though that its reaction time wouldn't be as fast as a wide band so I'd be a little reserved as using it as a tuning device. That is just my opinion as I've read many people using EGT as tuning devices successfully.

 

RACEPAK datalogging unit. Its plenty fast.

 

You are correct.
They are ungrounded probes according to your description.
Yes, they are overprices - typically $100 - $150 for a replacement.
This is the price you pay to use these Japan units.
I've only had to replace one probe, due to the casing split - probably due to debris hitting the probe itself.


-Ted