Oil temp sensor vs. kitchen thermometer in heated oil

[timotb]

My RV7A engine is showing low engine oil temperature in a new Lycoming IO_360-M1B with AFS3500EE. 130F at cruse. The spec sheet for engine oil temperature says the engine left the factory heating to 179F. Spoke to Lycoming, they suspect the probe. They suggested removing the probe and placing it in a beaker with heated engine oil with a standard kitchen thermometer and comparing temperatures. I used a simple electric griddle for the heat source. I recorded temperatures rising to 200 on the kitchen thermometer and temperatures falling back down after turning off the heat. I used, used automotive 10w30 engine oil. Any difference I think would be small. Below is the data I collected.

I spoke to someone at AFS the other day on this issue, they said to check the grounding. The probe is grounded with safety wire to an engine bolt.

Assuming the probe is not faulty and needs calibration, I see an adjustment for oil temperature under the administrative section. The next question is how much? I think setting it for accurate temperatures at 180 would be best. Rising temperatures at 180 were off by 60F on the EFIS, falling temps at 180 were off by 44F. Just guessing...start with an adjustment of 44?



AFS Oil temperature sensor on EFIS 3500 vs. Kitchen thermometer in heated engine oil in degrees F.
Rising temperatures

EFIS/ Thermometer
85 122
88 130
94 140
103 150
110 160
115 170
120 180
124 190
131 200
137 205
141 208

Falling temperatures

143 200
140 190
136 180
132 170
127 160
122 150
117 140
110 130
103 120

[Shawn McGinnis]

...low engine oil temperature...

The rate of change is a major factor in verifying any calibrated system. Ensure your achieving stable temperatures before you take a data point.

Some diagnostics that may help oil temperature readings:

1. Disconnect Engine Sensor Main Cable Pin 7 (Wht/Brn)
   
   • Screen should read AD_VALUE ~4095 and ~ -5.5 degF
   
   
2. Connect Engine Sensor Main Cable Pin 7 (Wht/Brn) to Ground
   
   • Screen should read AD_VALUE ~0 and ~340.0 degF
   
   
3. Connect Engine Sensor Main Cable Pin 7 (Wht/Brn) to 1KΩ Resistor through to Ground
   
   • Screen should read AD_VALUE ~2225 and ~65.0 degF

Looking at your measured table your average deviation would be a +34.5 degF adjust.

[timotb]

The temperatures were not stable during the rising and falling temperature test. The EFIS probe was lagging. Should I take another test reading trying to maintain a constant temperature, say 180 over 5 or 10 minutes?
Regarding step 3. Pin 7 is the main wire on top of sensor. You want the resistor inserted there? "through to ground" is confusing. Then do the calibration adjustment +34.5 to correct for error?

[Shawn McGinnis]

Should I take another test reading trying to maintain a constant temperature, say 180 over 5 or 10 minutes?

Yes for calibration you would want a stable oil temperature for say 1 minute, measure, then +20degF, then stable 1min, measure.

Regarding step 3... "through to ground" is confusing.

Hope this helps.

[timotb]

Yes it helps, but the probe/ sensor is not depicted.

[Rob Hickman]

Have you looked at this:

http://www.advanced-flight-systems.c...ouble-Shooting

1. The safety wire is not a good ground, your need to tightly wrap a bare wire around the probe threads and connect it to a good ground to test it.
2. Are you positive that you don't have a shift adjust value, item 10. Shift Adjust should be 0
3. Enable Admin mode, code is 1010 and email a picture of your Oil Temp calibration table to info@advanced-flight-systems.com
4. Are you positive that you have a 18ga ground wire tied to the EFIS case?
5. Where are you grounding the probe doing the test?
6. Is this our standard probe?

[timotb]

Went on a fourth flight today. Probe seems to be working showing temperatures above 140 and cruise temperature of about 173. I suspect I shook up the grounding when I removed the probe to test it. I assume I had a bad ground also during test. Hopefully the problem doesn't return. I'm happy now.

[NoahF]

I have nothing technical to add to this discussion.

However, I would just note that you are a brave man, using motor oil in a skillet in your kitchen. Or maybe you are a batchelor. I would MAYBE have used olive oil. Motor oil? My wife would kill me. When I painted my engine case and accessory housing, I "cured" the parts in the oven at low temp, resulting in quite a stink. Never heard the end of it!

[timotb]

I didn't heat motor oil in the kitchen. I did heat the water in the kitchen the night before using the same equipment. The heated engine oil didnt smoke.