Today's Message Index:
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1. 02:28 PM - Re: Jabiru 3300 CHT Disparity (BobP)
2. 07:16 PM - Re: Re: Jabiru 3300 CHT Disparity (FLYaDIVE)
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| Subject: | Re: Jabiru 3300 CHT Disparity |
I don't see how a CHT thermostat properly mounted in a small hole between the plugs
can do anything but record the true CHT temperature.
I can see how a thermostat crimped into an aluminium tag that is waving in the
breeze might not accurately display the temperature at the other end of the tag
(ie at the plug/head interface).
If the air blasting over this tab were to be increased (eg by fitting a baffle
that deflects and concentrates air onto the sensor tag) I would expect the thermocouple
temperature would reduce - even if the baffle restricted the total
airflow over the head so far that true head temperature increased.
If the above is true it would explain why the readings of sensors in the two different
positions give differing readings.
BobP
PS is there a text summary of the presentation that started this thread?
--------
BobP
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=406929#406929
Message 2
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| Subject: | Re: Jabiru 3300 CHT Disparity |
Bob:
Anything that changes the conductivity of heat between the spark plug and
the engine/cylinder will effect the CHT.
A spark plug is designated as a 'cold' or 'hot' plug because of the amount
of heat it holds. The LESS heat that is conducted off the plug makes the
plug a hotter plug. A hotter plug will cause the CHT's to increase.
Putting s Ring thermocouple under the spark plug cause LESS heat to be
conducted away from the plug which raises the heat range of the plug and
therefore the CHT's.
Also - Ring thermocouples read HIGHER because the heat range of the plug is
now increased.
I am not sure of what you are saying about a crimped aluminum tag? Would
you have a part number that can be researched online with a picture?
Barry
On Sat, Aug 17, 2013 at 5:27 PM, BobP <matronics@panth.co.uk> wrote:
>
> I don't see how a CHT thermostat properly mounted in a small hole between
> the plugs can do anything but record the true CHT temperature.
>
> I can see how a thermostat crimped into an aluminium tag that is waving in
> the breeze might not accurately display the temperature at the other end
> of the tag (ie at the plug/head interface).
> If the air blasting over this tab were to be increased (eg by fitting a
> baffle that deflects and concentrates air onto the sensor tag) I would
> expect the thermocouple temperature would reduce - even if the baffle
> restricted the total airflow over the head so far that true head
> temperature increased.
>
> If the above is true it would explain why the readings of sensors in the
> two different positions give differing readings.
>
>
> BobP
>
> PS is there a text summary of the presentation that started this thread?
>
> --------
> BobP
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=406929#406929
>
>
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