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CHT Disparity-Jabiru 3300

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Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Tue Aug 13, 2013 10:12 am Post subject: CHT Disparity-Jabiru 3300

I attended a forum at Oshkosh where a fellow discussed his research on cooling a Jabiru 3300.  He had compared the spark plug washer type CHT sensors to ones directly in the head and showed that they pretty consistently indicated CHT's about 70° cooler than actual temperatures!  If this is the case, Jab operators could be cooking their engines while thinking that their CHT's were within safe limits. He ended up designing a cooling baffling system that is nothing like what comes from the factory and claimed that was the only way he was able to get the CHT's under control.



I wonder what the rest of you Jabiru 3300 operators have to say about this? I'm not flying mine yet but will be getting ready to hang it soon.



For a summary on the fellow who made the presentation check out http://www.eaaapps.org/presenterinfo.aspx?id=1973



Tim

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_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

psm(at)att.net
Guest

Posted: Tue Aug 13, 2013 10:25 am Post subject: CHT Disparity-Jabiru 3300

Hi Tim,



I believe the Jabiru specifications are based on the spark plug sensors.



My 3300 is running just fine after about 50 hours.  It wanted to 

overheat at first but I reduced throttle to keep from getting it too 

hot.  Probably my first 10 or 15 flight hours were dedicated to making 

small changes in the cooling air flow and test flying. I have Dynon EMS 

with sensors on each cylinder and exhaust to monitor the temps.



One anecdotal experience I had was a big mouth engineer on one of the 

Jabiru lists who claimed all Jabirus had evidence of overheating on the 

cylinder bottoms.  I sent him photographs of mine, and after avoiding 

response he admitted my engine looked just fine with no suggestion it 

had ever been overheated.



When you let the cylinders get hot (not necessarily overheated, but 

warmer than is good) the cylinder head bolts tend to get a bit loose.  

You should check them regularly after first running your engine.



Good luck,



Paul

Camas, WA



On 8/13/2013 11:12 AM, Tim Juhl wrote:

 	  Quote: 	
		   



 I attended a forum at Oshkosh where a fellow discussed his research on cooling a Jabiru 3300.  He had compared the spark plug washer type CHT sensors to ones directly in the head and showed that they pretty consistently indicated CHT's about 70° cooler than actual temperatures!  If this is the case, Jab operators could be cooking their engines while thinking that their CHT's were within safe limits. He ended up designing a cooling baffling system that is nothing like what comes from the factory and claimed that was the only way he was able to get the CHT's under control.



 I wonder what the rest of you Jabiru 3300 operators have to say about this? I'm not flying mine yet but will be getting ready to hang it soon.



 For a summary on the fellow who made the presentation check out http://www.eaaapps.org/presenterinfo.aspx?id=1973



 Tim



 --------

 ______________

 CFII

 Champ L16A flying

 Zodiac XL - Jabiru 3300A

 Wing modifications done - back working on the fuselage





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