Jabiru Cylinder Head Modification for CHT sensor

[stevebetsy]

Hope I'm in the right forum here...did a search but found nothing similar.  Jabiru engineers posted six weeks ago a procedure to attach a modified sensor directly on the 3300 head and not under the spark plug.  Engineering report AVDALSR085.1 describes the procedure and justification for the upgrade.  I'm was getting ready to install sensors on my Jab 3300, but will wait now to see if Dynon or someone comes up with a 4mm sensor rather than modifying the 12mm plug sensor.  I would appreciate any advice if anyone has followed this procedure....it sounds like one would ruin a sensor or two before perfecting the technique.  Steve

 

[Dynon]

Any type J thermocouple will work. This may not be the exact thing you'd want, but there are (near) infinite variants of available thermocouples out there, such as:

http://www.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Temperature_Sensors_-a-_Transmitters/Thermocouple_Sensors/Sensors_(Bolt-on_Ring)/THMJ-B01L06-01

or

http://www.omega.com/pptst/wt.html

 

[stevebetsy]

Thanks....think I will modify the sensors had from Dynon...have a plan and will post some photos if/when I'm successful.

 

[lenene]

Instead of cutting off the 12 mm ring and soldering the two wires together and installing a ring connector, couldn't one just snip off the big ring circumference and drill a small screw hole in the remaining Y part and screw it onto the tapped hole in the head?

 

[stevebetsy]

Ooops...sorry...this should have been originally posted in the EMS section.

Here are a few photos showing the modification of a standard Dynon CHT sensor - P/N 100578. I decided not to shop for a new set of sensors...it was easier to just modify what I have from Dynon.

Grinding down the aluminum to accommodate the new sensor location went very well...die grinder + Dremel. The Dremel bit with teeth on the face was especially useful in getting into this tight space to flatten/finish the surface....not sure how I could have done that without this attachment.

I didn't follow Jabiru's engineering report to drill the hole out to 9/64"....used the 1/8" hole and tapped with 6-32...a loose fit; however, my experts tell me since they passes through >1/2" of threads, the grip will be sufficient for this application. And, if any of the screws become loose, high-temp Loctite will fix that.

 

[lenene]

to Stevebetsy= How does it work and do you see the same CHT values? The Jab service bulletin says use the same CHT limits although some previous entries on the web say otherwise. I think the values should be very close...

 

[stevebetsy]

Sorry...new engine....won't start up for a month or so. Will post some data when we get some. I'm keeping my fingers crossed!