Replacement EGT probe reading 60+ degrees higher.

[RandomSquawk]

In a Rotax 912: 4 years ago I replaced the left EGT probe, and today I had to do it again. Same Dynon part #. However, at cruise the new probe is reading about 62 degrees F higher than the previous one. I have no other indicators, sounds, or vibrations suggesting that the engine is actually, coincidentally, behaving different than it did 2 days ago (before the old EGT probe died). At room temperature, EGTL and EGTR match within 1 degree.
What could cause such a big shift at cruise temps, assuming nothing actually changed with the engine itself?

 

[jakej]

What method & or connectors & crimp tool? did you use for the wires ?
Regardless, I'd pull apart the connections, spray them with Contact Cleaner (re crimp if you used terminals) & re assemble - that fixes the 'issue' 99.9 % of the time. Remember we're talking millivolts so the connection/s have to be squeaky clean/crimped or screwed tightly to get good results.

 

[RandomSquawk]

What method & or connectors & crimp tool? did you use for the wires ?
...

They come with blade connectors pre-crimped. However, beginning 4 years ago, I cut off the crimped connector, strip 1/3" of insulation, and use a nylon split-bolt to clamp the wires directly to each other. After reading your comment about cleanliness, it occurs to me that I used my bare fingers to dress the end of the wire, and likely got contaminants on there.

 

[GalinHdz]

FWIW, I have found that those pre-crimped blade connectors are the cause of the vast majority of issues with both EGT and CHT probes. I cut them off and made the connection using wire overlap connectors ( https://www.aircraftspruce.com/catalog/inpages/eioverlapolc-1-10-05470.php ) which has eliminated problems. Note that you will need a 1/16, English-unit (ANSI/ASME) hex screws which is normally not included.

 

[RV8JD]

FWIW, I have found that those pre-crimped blade connectors are the cause of the vast majority of issues with both EGT and CHT probes. I cut them off and made the connection using wire overlap connectors ( https://www.aircraftspruce.com/catalog/inpages/eioverlapolc-1-10-05470.php ) which has eliminated problems. Note that you will need a 1/16, English-unit (ANSI/ASME) hex screws which is normally not included.

Cheaper from EI directly, and they include the Hex wrench:

OLC-2 Connector | Electronics International | Aircraft Engine Instruments

The OLC-2 eliminates the need for soldering, crimps, and expensive connectors, all while creating a perfect connection between two wires. The two wires are stripped 5/16"” and then slid into opposing ends of the OLC-2. A set screw on each side of the OLC-2 is gently tightened. The OLC-2 can...

iflyei.com

 

[RandomSquawk]

FWIW, I have found that those pre-crimped blade connectors are the cause of the vast majority of issues with both EGT and CHT probes. I cut them off and made the connection using wire overlap connectors ( https://www.aircraftspruce.com/catalog/inpages/eioverlapolc-1-10-05470.php ) which has eliminated problems. Note that you will need a 1/16, English-unit (ANSI/ASME) hex screws which is normally not included.

Kinda funny. I saw that and thought, "hmmmm, those look familiar". I did some digging around in my "box o' plane stuff" and found a bag of those connectors I purchased 4 years ago. I never installed them because my work-around held all this time.

 

[RandomSquawk]

tldr; Solved? New probes all around, all reading much hotter than the old ones. My new "normal".


I replaced all connectors with OLC-2. No change. Talked to Dynon support. They didn't have an explanation. On their advice I tried 2 more new sensors in the same (left) side with similar results. Then I put new sensor in the right side as well. Right side then read warmer, but still much cooler than left. I swapped left-right connections to check/eliminate wiring & EMS issues. Eventually I put the cowl back on, and went for a flight. Right side temps came up considerably, to mostly match the left. Cowl air flow differences? Both are reporting a lot warmer than the old ones, well into the Vans-spec'd warning range at sea-level & mid-throttle. At least they agree. The engine didn't just change over night, so I've adjusted my sense of "normal". I called Vans to see if there are new/updated EMS warning temp ranges since 4 years ago. They didn't know, and said "download the newest file and compare". Really? :\ I did. It hasn't changed. Then I talked to Rotech (real Rotax people), and they said "1540F" is pretty normal on a runup, and that I should adjust my warning range on the EMS. FYI, that's 70F hotter than Van's stock setup warning level, and much hotter than anything I've ever witnessed in any scenario. I don't trust any EGT value at this point. It's only good for relative minute to minute comparisons. They reiterated the Rotax book spec red limit of 1616F. I bumped my warning range up to 1530F. Gonna be a long time before I feel comfortable again.