UBG-16 and Garwin Cluster disagree. Significantly

[ragedracer1977]

On pretty much everything.  However, my biggest concern is the Oil Temperature.  The garwin shows oil temp at near 220.  The UBG-16 shows it at 105.  One of them is clearly wrong.  

My mechanical OAT shows about 20 degrees difference from the UBG.  Oil pressure is also different.

What should I look at to get this squared away, while I'm budgeting for an upgrade to a CGP-30P or a JPI EDM?  I wouldn't mind getting rid of the Garwin cluster altogether.

[Ron McBride]

Check the gauges and compare prior to starting and compare, they should all be close.

Ron

[ragedracer1977]

16 minutes ago, N803RM said:

Check the gauges and compare prior to starting and compare, they should all be close.

Ron

They are.  But in flight they are not, and that's concerning. Particulary the oil temp.  Am I near redline or at the bottom of the green?  That's a significant difference, and I find it hard to believe that my oil temp could be the same, or very similar to OAT - which is what the UBG is telling me.

[Vance Harral]

The traditional way to look at this is to remove the probes from their bosses while leaving them connected to their respective instruments, and drop them in a pot of boiling water.  Whichever one is wrong will be way off from 212 degrees.

[ragedracer1977]

That sounds like a great test!  If I find which one is off, is it more likely to be the probe or the instrument?

[Yetti]

Check to see where the probes are installed.   Have fun with one of those laser thermal thermometers right after shut down.

[carusoam]

Expect the probes are in different locations.  The one connected to the ship's gauge should be in the proper location so the oil redline is reading from a meaningful place.  Chase the wires to see where the sensors are located.

Your POH may have the detail of where the sensor is located.  

Best regards,

-a-

Edited June 15, 2017 by carusoam

[ragedracer1977]

I have one of those, I'll have to play with it.

[gsxrpilot]

If you're buying an engine monitor, after extensive research and experience, there are only three worth spending money on.

1. MVP-50 - Top of the line Primary
2. EDM-900 - budget Primary
3. G2 - budget

It all just depends on your budget.

[Bartman]

I have no experience here, but for multiple indication to be inaccurate I bet it's a ground issue. 

[N201MKTurbo]

The UBG uses thermocouples which are normally not inaccurate. They do have some failure modes. One is when there is a short in the lead wires. This forms a thermocouple at the short and will then read the temperature at the short instead of the probe. This sounds like what is happening with your oil temp.

The oil pressure uses a transducer which runs through an amplifier. There could be grounding issues between the transducer and the amplifier.

these are almost certainly installation issues and not the fault of the UBG 16. You could have the same problems with any of the scanners mentioned above.

[rbridges]

If your oil temp is 105, you have the most efficient cowl in the world.  I generally lean toward the engine monitors, but in your case, I think the analog gauge is more accurate.  Since your OAT is also different, I would do as others said and check for some type of ground issue.  

[Vance Harral]

19 hours ago, ragedracer1977 said:

That sounds like a great test!  If I find which one is off, is it more likely to be the probe or the instrument?

It's more likely to be the probe, but don't guess, determine for sure before buying any replacements.

Once you've identified which system is bad, you can test the probe for that system by measuring it with a multimeter.  The first test is to measure the resistance, which should be "relatively low" (not open circuit).  If that checks out, you can measure the voltage (for thermocouple probes) or resistance (thermistor probes) output when the probe is in the hot water, and compare against expected values in tables you can look up on the internet.

If the probes seem OK, you can check the gauges by applying a voltage or resistance across their leads, but that's a little riskier: it's possible to ruin the instrument by applying inappropriate inputs to it, so only do that if you're fairly confident you know what you're doing.

[HRM]

23 hours ago, ragedracer1977 said:

 I wouldn't mind getting rid of the Garwin cluster altogether.

I installed a MVP-50 (replaced the UBG-16) a few years back and since then have noticed all sorts of issues. One is alarming CHT's, alerts on vacuum and very aggravating alerts on low fuel.

I've concluded that it is all a part of the curse of accurate digital data. I have learned not to rocket up away from the airport and I keep my tanks fuller.

As for the vacuum, I think I am going to install a remote select/exit button to ease telling it to shut-up.

I still love the damn thing...