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engine monitor problem

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jonh(at)flinthills.com
Guest

Posted: Sun Mar 12, 2006 11:40 am Post subject: engine monitor problem

Hello group,



I am working on a Zenith 601 XL with a Jabiru 3300 engine.  We have installed an Electronics International MVP-50 engine monitor system.  Unfortunately, the system is not functioning properly.  Here are some symptoms:



1.  When the engine is not running, everything seems to work properly. 



2.  When the engine is running, we see the following:

    A. RPM value on display looks good   

    B. All values on the display associated with temperature (EGT, CHT, carb temp, oil temp) read very high and fluctuate fairly frequently

    C. All other values (volts, amps, oil press, fuel press, fuel flow, fuel level) seem to read accurately most of the time except they fluctuate regularly

    D. Error code "EDC" sometimes appears on various readouts (which EI says means the sensor hook-up box is sending nonsense to the display box)



3. The comm. radio seems to work fine with the engine running, and there is no appreciable noise.



4.  Engine runs great and shows no magneto/firing problems.



I have talked to EI, Jabiru, local electronics experts, and Bob.  I ran the sensor wires as far from the "loud" wires as I could in front of the firewall.  We tried running engine with one alternator wire (of two) completely disconnected.  This had no effect.  We installed a torroidal filter in the regulator output wire; this had no effect.  EI rebuilt the EDC-33P sensor hook-up box, and this had no effect.  We are contemplating having them rebuild the display box.  EI wants me to find an electromagnetic radiation intensity meter and take readings.



Can anyone shed some light on this problem?

andy(at)suncoastjabiru.co
Guest

Posted: Sun Mar 12, 2006 12:03 pm Post subject: engine monitor problem

Jon,



I know it's not very helpful to have someone reply with "I have no idea" but

at least you know the message was read!



We use other engine monitors like the Grand Rapids technologies EIS, Dynon,

Stratomaster, etc., and they all work fine if configured properly. This

means that I don't believe there is anything out-of-spec. with the engine

producing RF interference. I'm thinking it's the EI main unit not having as

good a noise rejection capability as other monitors.



Sorry I can't be more helpful.



Andy



Suncoast Sportplanes, Inc.

www.suncoastjabiru.com

--

jonh(at)flinthills.com
Guest

Posted: Sun Mar 12, 2006 8:39 pm Post subject: engine monitor problem

Andy,



Thanks for your interest.  Maybe this is just one of those unpleasant 

learning experiences where we have to give up and try a different product.



Jon



---

JAPhillipsGA(at)aol.com
Guest

Posted: Mon Mar 13, 2006 6:21 am Post subject: engine monitor problem

Any chance your strobes are effecting it ? Maybe you should us shielded wire.

pkrotje(at)athenet.net
Guest

Posted: Mon Mar 13, 2006 6:25 am Post subject: engine monitor problem

Jon,



Try totally disconnecting the regulator.  Let the engine run and all

avionics power come from the battery with no charging input from the

alternator and no chance of noise from the regulator.  You may not get a

tach input with the alt disconnected but if regulator or alternator noise

was the problem the rest of the sensors should work right.  



Let us know if it makes any difference.  It sure looks like it is EI's

problem, though.



Pete



--

jonh(at)flinthills.com
Guest

Posted: Mon Mar 13, 2006 2:42 pm Post subject: engine monitor problem

Thanks for your response.



The strobes have been off during all our tests. I mounted the strobe power 

supply box under the seat, so I don't think I will have a problem.  I 

suppose we'll have to run that test after we fix this problem to verify 

proper function.



---

jonh(at)flinthills.com
Guest

Posted: Mon Mar 13, 2006 2:59 pm Post subject: engine monitor problem

Thanks for your response.



So you're saying I might be getting noise from the regulator even if the 

alternator is disconnected?  I'll try that test tomorrow.  I talked to Bob 

N. on the phone today, and he had me run a test with the P-leads 

disconnected at the mags.  This didn't help.  He wants me to run the MVP 

system off of a different battery all together.  One thing I haven't 

mentioned before is that we installed an EXP cockpit power control unit.  [I 

noticed that Bob is not fond of these things while reading one of his 

archived debates.]  It has an integral switch panel , master relay, and 

solid-state breakers.  Is it possible that this gadget is somehow 

misbehaving in a way that would not show up on an oscilloscope?  We put an 

oscilloscope on the power wire to the MVP system about 2 weeks ago with the 

alternator hooked up.  It seemed to indicate that we were getting constant 

12.4 volts, and that the AC portion of the power input was about 24mV at a 

frequency corresponding to 12 times the engine RPM.  This made sense to me 

since the alternator has 12 spinning coils.

---

Jim Stone

Joined: 24 Apr 2006
Posts: 4
Location: Clearwater FL USA

Posted: Mon Apr 24, 2006 7:32 pm Post subject: Re: engine monitor problem

You might be experiencing a ground problem rather then a noise voltage.  A single point ground is recommended.  CHT's and EGT's output millivolts which make them sensitive to ground current loops and noise.



You might also want to do an oil bath calibration of the CHT probes to verify that the displayed reading is reasonably accurate.  You can pick up a wireless digital thermometer for less than $30 at most Ace hardware stores.  Running the test with probes floating and grounded may give significantly different results.



Good luck.

_________________
Jim Stone
Jabiru J450 N450SJ
Clearwater FL USA

JAPhillipsGA(at)aol.com
Guest

Posted: Tue Apr 25, 2006 8:34 am Post subject: engine monitor problem

Jim, I think I will try to test my probes as you suggested. Again, how would 

you do that ? I have a digital thermometer so would I have to get some water 

hot and stick the thermometer probe and the CHT probe in there together and see 

the difference in readings ? You mention grounding. Would I have to run a 

ground wire from the CHT probe to the engine ? I remember when I purchased the 

CHT kit the instructions mentioned that they could be off by as much as 75 

degrees. Best to you, Bill of Georgia, N505WP, 601X-3300 w/dc and 60 plus hours 

do not archive

Jim Stone

Joined: 24 Apr 2006
Posts: 4
Location: Clearwater FL USA

Posted: Tue Apr 25, 2006 6:50 pm Post subject: Re: engine monitor problem

When I calibrated my CHT's I set up about a pint of engine oil in a flat bottomed pot.  Heat was provided by a fondu warmer.  I got the pot a 'Bed Bathe & Beyond as a lidded canister for about $5.  (My wife said OK to using the heater, but not the matching pot.)  This gives a reasonable temperature ramp and can go to above boiling without agitation.   I use a couple twists of safety wire to keep the sensor and thermometer probes together.  A heavy alligator clip provided the ground.



The ground should go directly to the engine block.  My sensor outputs shifted by a factor of 3 between grounded and ungrounded tests.  My sensors have a metal mesh shield but it turns out is is just for abrasion, it was not grounded at either end.  The sensor also had a resistance to ground in the low milliohm range.   Obviously, in use the grounded configuration is the real world environment.

_________________
Jim Stone
Jabiru J450 N450SJ
Clearwater FL USA

JAPhillipsGA(at)aol.com
Guest

Posted: Wed Apr 26, 2006 6:27 am Post subject: engine monitor problem

Jim, thanks for the input. I plan to try testing this weekend at the hanger. 

What kind of difference did you find ? and did you check all your CHT probes 

or just the hottest ? I don't want to make extra work for myself as every 

minute working - is a minute flying, Thanks, Bill of Georgia

do not archive

Jim Stone

Joined: 24 Apr 2006
Posts: 4
Location: Clearwater FL USA

Posted: Wed Apr 26, 2006 3:22 pm Post subject: Re: engine monitor problem

My tests were more complex then you would typically encounter.  This was because I was testing a custom design before general public release.  The firt set of softeware coefficients gave results that were nowhere near the real worlk, Ref temp = 385 'F vs displayed value = 223' F.  variation between sensors varied by up to 20% of reference standard.



We eventually scrapped the initial hardware and went to differential sensors for each line.  The process took several months between hardware and software revisions.  All sensors are now +/- 3% of my calibrated reference.



The Great Lakes sytsem has enough volume that I would expect all sensors to show in the range of +/- 5% compared to a reference standard.

_________________
Jim Stone
Jabiru J450 N450SJ
Clearwater FL USA

JAPhillipsGA(at)aol.com
Guest

Posted: Thu Apr 27, 2006 6:59 pm Post subject: engine monitor problem

Jim, I conducted my CHT probe tests this afternoon as you described with the 

hot oil and they were very accurate. Good for peace of mind. Thanks for the 

assistance. Best regards, Bill

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