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tonyplane(at)bellsouth.ne
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 Posted: Wed Apr 26, 2006 5:01 am Post subject: engine monitor problem - CHT thermocouples |
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Bill,
If your CHT probes are attached to your monitoring instrument, then all you
ahouls have to do is put the "sensening" end of the probe into a know temp
liquid and check your instrument reading. I used to check calibration by
placing the "twisted" end of the thermocouple wire into ice water (32 deg
F/0 deg C) and then into boiling water.
Another thing to do to check the CHT thermocouple position for instrument
reading is to use a hair dryer or other hot air device to put heat onto the
cylinder and check the reading on the instrument. I found that I had two
cylinder location readings reversed when I installed my probes.
Tony Graziano
ZodiacXL/Jab3300A, N493TG, 91 hrs
Time: 09:34:00 AM PST US
From: JAPhillipsGA(at)aol.com
Subject: Re: Re: 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
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JAPhillipsGA(at)aol.com
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| Posted: Wed Apr 26, 2006 6:56 am Post subject: engine monitor problem - CHT thermocouples |
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Tony, thanks for the input. I to had two cylinders probes reversed. My real
concern is how much attention I need to pay to the gages. I noticed the other
day that my oil temp went up as the CHTs for 4 & 6 stayed up and moved down as
they went down. I wonder how accurate my oil temp gage is ? Is there a way to
mechanically test this ? When I first started flying her I used a mechanical
gage to test the oil pressure gage and found it reading 10-15 pounds high. Have
you tested yours ? I will be glad to send you the oil gage I used and
fittings if you want. Thanks again, Bill of Georgia
do not archive
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tonyplane(at)bellsouth.ne
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| Posted: Thu Apr 27, 2006 4:52 am Post subject: engine monitor problem - CHT thermocouples |
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Thanks Bill,
I suppose that you could also put the oil temp probe into boiling water
(with it grounded to the engine) and check your temp gauge for a 212F/100C
reading. I find mine reads the same temp as the CHTs (within a couple of
degrees spread among all readings) when the engine is cold, so I am assuming
that the hot readings are OK. My oil press probably reads a few pounds high
as I show 4psi before start, but that does not concern me. I tried another
VDO oil press switch and get about the same readings between the two. I
also attached a red LED to the WK switch (the idiot light switch) on the
VDO, through a relay, which lights up before engine start (zero oil press)
and at very low oil press. It is reassuring to see the LED go out at engine
start up.
I have to watch CHT and oil press when the ambient temp is warm to hot. If
I keep full throttle in climb.below 90 kts I will start approaching red
lines in CHT and oil temp. If oil temp goes near red line, then my oil
press starts to drop. I am using EXon Elite 20W50 oil. My instrumentation
is the Grand Rapids EIS - (It is a really neat instrument - if you go to
max or min for any set parameter, a large red light blinks at you.)
Tony Graziano
Zodiac 601XL, 493TG
Time: 07:56:51 AM PST US
From: JAPhillipsGA(at)aol.com
Subject: Re: Re: engine monitor problem - CHT
thermocouples
Tony, thanks for the input. I to had two cylinders probes reversed. My real
concern is how much attention I need to pay to the gages. I noticed the
other
day that my oil temp went up as the CHTs for 4 & 6 stayed up and moved down
as
they went down. I wonder how accurate my oil temp gage is ? Is there a way
to
mechanically test this ? When I first started flying her I used a mechanical
gage to test the oil pressure gage and found it reading 10-15 pounds high.
Have
you tested yours ? I will be glad to send you the oil gage I used and
fittings if you want. Thanks again, Bill of Georgia
do not archive
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JAPhillipsGA(at)aol.com
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| Posted: Thu Apr 27, 2006 6:57 pm Post subject: engine monitor problem - CHT thermocouples |
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Tony, I conducted my CHT tests this afternoon and the results were dead spot
on. Course I did not get the oil bath temperature up above 175 as hot oil can
be a problem, but the probes were very accurate up to that point. I' going to
fly into a little fly-in at Larenceville just east of Atlanta Sat morning.
Nice field and folks at the EAA chapter put on a fine breakfast. Several other
601's are bound to be around. Maybe you could make it. Best regards, Bill
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