Greetings Jabiru engine users and enthusiasts,
I'm operating an A2200 on my recently purchased ELSA Romanian built Aerostar 1 (this was the prototype that is now superseded by the Festival RS40, powered by the Rotax 912).
The engine is equipped with a VDO M12 CHT sender using a ring terminal that is fitted under the spark plug. The previous owner had it disconnected as the ring had split - probably by the constant removal of the spark plug. I was looking at the 3300 installation, DOCUMENT No. JEM3302-7, and due to the fiddly nature of centering the ring, etc., Jabiru recommends installing the CHT sender terminal on the bridge between the spark plugs with a 5/32" machine screw – obviously, not using the M12 ring terminal if using the VDO sender thermocouple wire.
I believe that installation option is recommended as it is already threaded at the factory for the 3300. I don't recall seeing that on my A2200. I'm reaching out to this forum to ask if this has been done/attempted with your Jabiru 2200 and if you could share your experiences and or recommendations.
I tried purchasing a new replacement from Aircooled.net but it is not in stock, thus back-ordered. And perhaps with good reason; my understanding is that VDO no longer manufactures the M12 version and only the M14.
Cheers,
Alex R.
Hello Jabiruyank,
We still stock the 12mm senders. Also the space between the spark plugs can be modified to accept the 4mm cht senders as used on later engines (8-32 screw).
Regards
Hello Jabiru support,
Thank you for replying. The 4mm seems the more practical option as one doesn't have to fiddle with the spark plug and proper contact. I assume it's a simple matter of drilling to the right depth and tapping the hole to 8-32.
Is this sender available through Jabiru, and if so, will it work with the VDO gauge I have installed on my aircraft? Sorry, I don't have the VDO model number handy if that's needed.
Hello Jabiruyank,
It is slightly more indepth than that. A dremel or die grinder needs to be used to make a flat place for the ring to screw down on before drilling and tapping.
Yes we have vdo cht senders with a 4mm ring. I don't know if our US dealer has any in stock.
Greetings Jab support,
Thanks for the photo. My head appears to be different and does not have that cast “step” directly below the head bolt hole. It appears to be further down about 18mm from the center of the bolt hole as compared to the photo you attached. Please see attached photo. The serial number of the 2200 is 22A 981. Is it possible to drill and tap just under the head fastener hole? Looks like I would have to “hack” off quite a bit of fins to get at the step 18mm from the center of the bolt hole. Thanks!
Alex -
Jab support,
i apologize for so many posts but I don’t see the ability to upload more than one file. This is a second shot of the head with the plugs removed and the black marker lines denote where I’ll have to cut the cooling fins. Your input is greatly appreciated!
Thanks,
Alex R.
Hello Alex,
I see your problem. And no I see I have led you the wrong path. With heads like yours (we call them coarse fin heads) there isn't enough metal around the spark plugs to put in the cht like on later engines.
The best solution on these heads is to put the cht ring under the exhaust side spark plug and when doing services only remove the inlet side spark plug. This reduces wear and tear on the ring.
Thanks again for your help Jabiru support. I guess hacking away at the fins, drilling and tapping isn't going to work with these older style heads - pity. And I already bought four 4mm CHT senders from Arion Aircraft. I’m not a fan of the 12mm sender under the spark plug as it doesn’t lend to removing the spark plugs off for inspection regularly without buggering up the sender/washer. Oh well. I’ll use it for now on the #4 cylinder until I figure out a long term solution. It’s better than no CHT reading at all ... Thanks again,
Alex R.
Hello Alex,
I had another thought, on those heads there is some holes that go through from near the spark plugs to the underside of the head. Near the ports. For awhile CAMIT had probes that went into one of the holes, for cht measurement, when running the engine on the dyno.
If you were willing to do a bit fabrication you might be able to fit a piece into the lower hole that you can attach the cht too.
If you got that to work then all you would need to do is compare the temperature reading between the ring and the new location.
Thanks guys very useful - this is the same issue I have.
Attached is a pic of my 3300 heads. Do I need to tap the hole between the spark plugs or is it already tapped? What is the thread of the 8-32 screw? Is it metric? UNC? is it an 8/32" screw? Is it (Sorry for the basic questions).
Toby,
Couldn't open the picture. However if the hole hasn't already been used for the cht it probably isn't tapped. However it is an 3.2mm plain hole which you can tap to 8-32 unf. Then we use the shortest 8-32 pan head aircraft screw (MS35206-241) to hold down the cht ring.
Thanks!!
