Hi Martin,
I also recently had to contemplate new, non-rotax CHT probes for my
new Gen 4 Blue Mountain EFIS. BMA also supplies non-thermocouple
sparkplug ring electrodes. The problem is that an engine block is
not simply a homogeneous single temperature when operating. Measuring
---From different places will definitely give you different values. Measuring
---From a sparkplug or from the outside of the block will give you nice
consistent values, BUT you can NOT apply the official factory limits and
critical values to those off the mark readings. Kerry at Lockwood
confirmed this opinion. Kerry, BTW, is the single most experienced
Rotax A&P in North America to my knowledge (save Eric Tucker).
Rotax CHTs are quite particular due to the metallurgy of the head.
You could measure both standard probe and your rings together for a
while and find the offset between them and then apply it to new
limits on CHT for your plane.
The easier approach in my opinion (at least it was for me) is to get the
manufacturer to offer a calibration for the standard rotax probes as an
option. The complete cal curves are available on the VDO site and I was
able to deliver these to BMA. Its really all they need to let you use the
original Rotax probes. The probes after all use the same technology, just
different scale factors.
--------
Ira N224XS
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