Wal

Great to read the different replies. I guess the only point I am making is to check the thermocouple in boiling water whether or not it seems to be in the right range, just to check and be sure. It only takes a few minutes at the next annual. Whether the thermocouple should be above or below the plug washer is a good question and can be easily checked by shifting it and seeing if there is a significant difference. I intend doing this at my next annual. Thanks for the interest, I have learned heaps.

J, Yes I have the Thermocouple against the head. Although the VDO manual says to remove the washer, Jabiru say that they leave the washer intact, but with the thermoucouple between it and the head. I would assume that if you did put the washer under the thermocouple then the reading would be cooler not hotter. Wal

J430, I guess that VDO produce gauges to an acuracy that would be expected for automotive use, whereas we require a more accurate reading. But this is not an excuse for selling an inacurate gauge. About testing, I guess I should have put it into boilong water sooner, but I assumed that the problem was with something I did in the instalation. Andy, yes the EGT is also a thermocouple, and no I did not get it tested. I am thinking that I should, although it at least had thermocouple cable, what the two metals are I don't know but at least they are different and not just both copper. Yes I have sent a copy to Michael at Jabiru Engines as he has been e-mailing me for some time as we worked on the problem. I have also sent it to any Jabiru owner I know, not that I know many yet, since there is none around here. I guess a reply from Michael might hint to what the factory models have as wiring. Thanks for your replies.

G’day everyone I have had a problem with the CHT running too high in my Jabiru J230 ever since I built it. The following story might interest you. My Jabiru J230 was experiencing an assumed heating problem. After having the Jabiru climb with the CHT just in the red (400 deg) and cruise in the yellow (360 deg), I attempted a number of things to reduce the temperature. Firstly I have babied the aircraft to keep the temp down (which was not good in the run in period). I waited to see if the temperature reduced as it ran in as suggested. It did, but only slightly. I modified the cowl as suggested by Jabiru by adding the two small deflectors on the bottom (even though the CHT was the only problem, oil temp has always been low). I changed the carby jets to enrich the mixture and therefore make the engine run cooler (added an EGT and have reduced EGT with the richer mixture). It is now running the recommended 20 Lt/Hr. fuel use. I centred carefully the thermocouple under the spark plug, because evidently if it is not centred then the reading can be high. Considering that the EGT and oil temperature were quite low (oil temp 70 – 80 deg), I surmised that the engine did not seem to be running hot, therefore I should test the CHT gauge itself. I removed the thermocouple from the spark plug and placed it in a boiling jug of water. The CHT gauge read about 230 – 240 deg F. Much too high so I removed the whole gauge and thermocouple and sent it to John Press at Australian Aviation Specialists in Tamworth for testing. John also consulted a colleague Keith Jones at Sigma Instruments in Tamworth. John and Keith found the gauge and the thermocouple tested okay, using various test equipment, so suggested that it may be a problem with the wiring or connectors as these can affect the resistance, voltages produced at junctions and therefore the voltage that reaches the gauge. Incorrect wiring types can also generate errors as every time the type of wire is changed it forms another thermo couple at the joint. They connected the thermocouple and gauge with the similar copper wires as supplied with the VDO gauge and found that the result was variable and inaccurate. They tried a few different wire types and found that if they used Iron Constantan wire the results were accurate and consistent. They confirmed the results by connecting again with the copper wire and again the results were inaccurate. After supplying me with the right length of Iron Constantan wire I was able to test the CHT in the aircraft. I first tested it in boiling water as a comparison. The gauge now indicates about 208 - 210 Deg F with the probe in boiling water which is about right for our altitude of 3500 feet AMSL. In the aircraft it now always runs in the green, mid green (275) in cruise and higher (320) in climb. Great! It has been a long road but it is reassuring to know that I had not been overheating the engine prior to the correction. My experience suggests a question for other Jabiru owners who are having problems with CHT that may possibly be caused by the wire supplied with the gauge. How many problems are not engine heating problems at all? Are others running engines with CHT under reading? Iron Constantan wire is evidently not commonly held in stock because it is quite expensive. John Press at Tamworth now has a supply of this wire and is also available for any questions and advice about what he has found with my aircraft. I have added his contact details for further technical information. John Press, Australian Aviation Specialists, Hanger 6, Tamworth Airport E-mail: [email protected] Phone: 0427-681-893 I hope this has been of interest.

Wing Root Breather connection Geoff, on memory I had 2 assistants hold the wing down at an angle so that the bottom of the wing skin was nearly touching the fuselage. This gave just sufficient space to get the fingers in and attach the hoses with the aid of pliers (with tape over the jaws so they would not damge the hoses). But it ain't easy. If my memory also serves me correctly, it took a couple of times to get the hose lengths just right so that they would not kink when the wing was lifted back into the strut. Have fun! Wal

Thanks Allan, after my tougue in cheek comment about high altitude airstips, you got me looking up the acuracy of my comment. I appears that we are still both right, Cabramurra has an atitude of 5080 ft, 500 ft above Guyra, but Mt Hotham, that I assumed was high is only 4260 ft, Cooma 2700, Khancoban 960 and Talbingo has closed. Wal

Hi Graham, Are you at Cobar airport or on a property where building codes for sheds don't apply? I have built a very economic hanger on our property near Guyra NSW (near Armidale for those who don't know the second highest airstrip in Aus. except for Mt Hotham). My hangar for our J230 including doors, is made out of out of hail damaged iron (although you would be pressed to see the damage), box posts from our place, and trusses manufactured here by a Boilermaker mate that has welded trusses since the 70's. Doors are bi-fold verticle and work very well. We have had to strengthen the door latches to overcome some of the storms we get here but the general design is good. If interested I could post some photos and dimensions. Wal.