Message text written by INTERNET:TroyMaynor@aol.com
>I have been asked by the company furnishing an engine monitoring system to
specify the thread size for a water temperature probe. I will be using th e
912S. Since there is no provisions for a water temp probe, where and how to
mount such a probe? Do I even need it with 2 CHT pickups already in place ?
Are these two probes already threaded into a water jacket? I'd feel more
comfortable monitoring both CHT and water temp. What do you all think? I
realize there has been some discussion of this in the past months but I
somehow missed part of the responses.<
You do not say which monitoring system you are using. The existing sender s
are not compatible with the RMI Monitor system which I am using. RMI
provide useful contacts for manufacturers of alternative CHT and carb
temperature probes.
I had two adaptors made up to accommodate 1/8" NPT threaded senders to
replace the metric CHT senders. One enabled me to use a thermocouple prob e
to measure water temperature the other was used for water pressure (this
should sense problems with the water system quicker than temperature
measurement). I think that as the Rotax uses water cooling for the heads,
conventional CHT measurement is probably superfluous.
> Also EGT; since my exhaust system did not arrive yet will it have the
welded
bosses for a threaded fitting or will I have to drill holes in the pipes to
fit the clamp on type. And do I use the 1/2" or the 1" EGT probes? <
The clamp type mounted about 2" from the head was easy to fit and has bee n
used by other builders. Due to the small bore of the exhaust the 1/2" pro be
is plenty long enough.
>Carburetor Temp- Is this necessary? How would a sensor be mounted,
especially
since you've got two to deal with? What thread size is appropriate?
<
The Rotax engines (when mounted inside a cowling) do not seem to suffer
---From carb icing (hence no carb hot air control). However as carb temp can
be displayed on the RMI system, for the sake of purchasing and fitting th e
necessary sender, I decided to include carb temp. I only mounted a single
sensor (assuming that the carbs should be at similar temperatures). I
drilled a hole near to the throttle butterfly and tapped with the
appropriate thread (1/4"/28 in my case). A combination of washers ensured
that the probe didn't protrude too far into the carburetter throat. Redux
was used to provide extra support and thread locking. When drilling using
plastercene (or similar flexible material) on the inside will prevent swa rf
getting into the carb.
Nigel Charles
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