Today's Message Index:
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1. 03:29 PM - Re: Kitfox-List: CHT probe placement (Lynn Matteson)
2. 10:02 PM - Re: CHT probe placement (Jim Crowder)
Message 1
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| Subject: | Re: Kitfox-List: CHT probe placement |
I did some tests today regarding the CHT probe placements on my
Jabiru 2200 engine. I'm cross-posting this so others can benefit, and
even make assumptions regarding other engines, perhaps. I was
wondering out loud about how the different mounting locations for the
thermocouple probes might affect the readings of the cylinder head
temps. During my recent overhaul, I decided I didn't like the "under-
the-spark-plug" mounting location, so I changed to a location that
required me to drill into the head, tap it for an 8-32 machine
screw...actually a socket head cap screw...and affix the proper
electrical terminal onto the end of the t'couple probe...after
removing the spark plug terminal of course.
First I went up and got some CHT numbers as the basis for comparison.
I noted that cyl. #1 ran 317, 327, and 340 F, during various phases
of flight. Noting these, I then took the probe from cyl #3 and
attached to it a spark plug terminal (12mm), and installed it onto
the spark plug that lives over the exhaust valve on #1 cylinder. I
first removed the spark plug washer like Jabiru says to do, installed
the probe/terminal, then reinstalled the spark plug washer, and
reinstalled the plug. Then went flying again.
Here is how I'll report the numbers....I'll call the new location
(the machine screw termination) CHT, and the spark plug termination,
SP, as In (CHT/SP)
The numbers I got were as follows (with an ambient of 61 F) (drum
roll please)....initial taxiing= (250/220); taxiing further=
(266/230); climbing out= (308/232); further climbing=(321/243);
leveling off (not recorded for how long level)= (330/245); not noted
what attitude, but not climbing=(334/249); climbing again briefly=
(344/248) I noted that the max differential was 96 F, and the
climbing EGT's were in the high 1200's. I didn't have enough hands,
instruments or inclination to record every aspect of the test, but I
got enough to satisfy myself that my new locations for the CHT probes
work, and now I can rest assured that I'm not overheating the engine
as I thought I might when I first started it up with this
configuration. Needless to say, the CHT's now apparently rise more
quickly, and if you're like me, and you've been accustomed to seeing
it rise slowly and only into the low to mid- 200's, the ol' pucker
factor rises just as quickly and the finger gets close to the panic
button, but it's just numbers, and now that I've done some testing,
I'll relax a bit on this subject at least.
Lynn Matteson
Kitfox IV Speedster
Jabiru 2200, 562 hrs, and counting...all systems are go, or nearly so...
Message 2
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| Subject: | CHT probe placement |
Lynn,
I have decided to use the factory holes on my 3300 and surface mount the
sensors using the 8-32 machine screws. Did you use steel, stainless steel,
or aluminum screws? I am thinking maybe aluminum if I can find them. I can
guess what the issues might be.
Jim Crowder
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