During my first few hours of flight, I experienced some elevated cylinder head temperatures on my Jabiru engine. The following is a summary of changes made to improve the situation. This really just builds on the recommendations of Jabiru and Zenith to provide plenty of cooling for the 6 cylinder engine. I would like to thank Jeff Small, Fred Hulen, Stan Challgren as well as Pete Krotje at US Jabiru and Andy Sylvester at Sun Coast for their contributions. As a place to start, US Jabiru provides some good cooling suggestions at their website: http://www.usjabiru.com/Zenith fwf.htm http://www.usjabiru.com/Tech Tips.htm My aircraft has the following modifications: Gull wing baffles between cylinders as recommended by Jabiru Full deflectors angled down between the spark plugs of cylinder #5 & #6 as recommended by Jabiru. Smaller deflectors angled down between the spark plugs of #3 & #4. These middle cylinder deflectors usually need some tuning. Would suggest starting with 3/4" tall. On #3, I stayed at 3/4", on #4 ended up trimming down to 1/2". The inlet to the ram ducts allows some air to escape downward. I added some .025" aluminum extentions that butt up against cylinder's #1 & #2 to prevent this from happening. On cylinder #1, I angled the material upward about an 1" to reduce airflow through this cylinder which tends to run cooler than the others. Small baffles mounted between valve tappet covers. There is a temptation to add an L angle to the bottom rear of each ram duct. I tried this change and it elevated my temps rather than reducing them. The oil cooler inlet is keep quite small to allow more air to find it's way through the cylinders. I ended up with about 1.5" x 4.0" opening. The Jabiru website provides a good discussion on this. I'm planning on adding some additional ducting on the exit of the cooler to force air through the fins on the bottom of the oil pan. Another suggestion from Jabiru is to lower your oil level to 1/2 way between the full and add marks on the dip stick. These two changes should lower my oil temps further. With the Aid of my Engine Imformation System from Grand Rapids Technology, I was able to monitor my progress for each Cylinder Head Temperature: I now have the following readings at 80 F ambient tempertures (my engine has only 4 hours TT, so temps will decrease after break-in): Climb: #1: 259, #3: 317. #5: 313
#2: 322, #4: 274, #6: 273
Oil Temp: 230 F Cruise: #1: 225, #3: 264, #5: 257
#2: 274, #4: 261, #6: 269
Oil Temp: 210 F Hope this provides some useful insight for those planning to use this great running engine. Chuck Long
N601LE, 5 hr TT | 
