I've been using the Greddy EGT gauge and probe on the #2 runner on the exhaust manifold for about 6 months and really like it. Recently, I bought a Zeitronix ZT-2 and got an EGT harness to splice into the Greddy gauge, because I didn't want to make another tap for a second probe.

So, I got both gauges connected to the 1 probe, and when I went WOT, I was seeing 1100C temperature... well over the normal 800C I see on WOT. After verifying that my motor wasn't melting, I figured out that the reading was due to having 2 gauges connected to 1 probe. Anyone else experience this? Is there some kind of resistor that I can have on the connections to prevent this from happening?

 

No experience, but I can see how it could go wrong. Either the thermocouple will generate a weak voltage with a bit of current or the thermister will change in resistance value. Which ever way your measurment system was designed, you'll be loading the reading the wrong way by throwing an additional load across it in parallel, changing the the voltage divider network or bridge.

That's why you go Apex'i EL2 gauges

I'm unsure if a simple resistor will help until you understand the electrical design differences between the two measurement devices.

 

Anything you spliced together is now junk. EGT probe wires are a specific length and material for a reason.... any variation will throw off the readings. The output of the probe is very small in magnitude and any interfearence from corrosion at junktions etc can throw off the reading a lot... I am amazed it worked at all with the splice job.

Keith