On Aug 11, 2010, at 9:40 PM, Rotary Engine wrote:

 Hi All,

 Has anyone thought through how to wire the stock RX8 coolant
 temp sensor to a Dynon GP Input? Any info on specifics of
 the sensor is also appreciated.

 Thanks in advance,
 --Kenny A.

 Do you have the instructions for the Dynon Kenny.
 You need to know what kind of sensor it requires.
 You also need a calibration curve for that sensor.
 Resistance verses temperature.

 The ECT Engine Coolant Sensor in the RX8 is the thermistor
 type.

 "Thermistors are thermally sensitive resistors whose prime
 function is to exhibit a large, predictable and precise change
 in electrical resistance when subjected to a corresponding
 change in body temperature.  Negative Temperature Coefficient
 (NTC) thermistors exhibit a decrease in electrical resistance
 when subjected to an increase in body temperature and Positive
 Temperature Coefficient (PTC) thermistors exhibit an increase in
 electrical resistance when subjected to an increase in body
 temperature.  Because of their very predictable characteristics
 and their excellent long term stability, thermistors are
 generally accepted to be the most advantageous sensor for many
 applications."

 I am not sure if the RX8 is a PTC or NTC type. Use an ohm
 meter and place it in boiling water. You can then calibrate it
 and compare the calibration curve with the Dynon type.

 Paul Lamar


Automotive ECT's are negative. The lower the temp, the higher the
resistance.
This allows less current to flow and the ECU "see's" higher voltage. This
richens the mixture like a choke. As the coolant warms, the resistance
gets
less. The ECU see's less voltage, thus less fuel. On the ECU board
there are
resistors just before the terminal to the sensor. There is an internal
take
off for it to sample the voltage, between this resistor and the sensor.
Test to your heart's content though.

Dale Davies

Dynon does not publish a spec for their sensors. Their GP sensor is the
same as their oil temp sensor. If you bought the sensor package and have
the oil sensor, compare it to the RX-8 for resistance vs temp.  If they
are not the same, it is unlikely you will be able to rig to get accurate
readings.

Victor

Thanks all, this is plenty to get me started. Attached is
an excerpt from the installation guide. Looks like the
right combination of voltage divider / gain and anything would work.

--Kenny A.

That is pretty blurry Ken. Can you scan it at higher
rez?

Paul Lamar


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