Intersting find

[LarryEWaiex121]

Last flight out on my Jabiru powered Waiex, I noticed on taxi that the #2 cylinder was showing an out of the ordinary egt at low speed, (1,000rpm). I was showing maybe 1100 degrees and the others were barely registering on the Dynon.
At the 1600 run up speed the egts all pretty much lined up. I made a mental note to check the egt on that cylinder next time I had the cowling off.
On the flight I was watching the egts and chts to see if there was any difference than what I was used to? Nothing out of the ordinary.
Just for reference, the #2 cylinder has aways been my warmest since day one. Number 5 and 6 have always been the most balanced and consistly run within 5-10 degrees of each other. Number 2 out front always runs about 15 degrees higher than the rest.
I began to notice on this last flight that making a couple different climbs and decents of over 3,000" each, the #2 was acting funny and getting hotter than normal. I got it up to 345 indicated on an extended climb. Now it is pretty warm out west but it still was off from the rest and by almost 35 degrees. Much more than I'm used to.
The following day I pulled the cowl and decided to run the valves at their normal 50 hr check and got that accomplished. While I had the shrouds off I decided to pull a "cold" leak down test on #2. Much to my displeasure I found it to run at 80/64. Down significantly from the last inspection. Factoring in the cold check it still seemed too much of a change for me. I pulled the head to look hard at the exhaust valve in particular. Nothing to note that seemed out of the ordinary. Stems were clean looking in the ports. No burn marks of any kind near the seats and valve face.
Honestly, I believe in my case the loss of sealing is around the rings. You can hear the air out the breather. All the other cylinders are running 80/75 or better. Will pull the cylinder also and hone the bore and scotchbrite the piston and clean the ring grooves. My halfway, one cylinder tune up. Hopefully this will get me to my top end rebuild I'm hoping to do about 600hrs or whenever the engine tells me its time. I'm setting at 440 hrs now; other cylinders are doing fine.
Dropped my cylinder head off at a place that has considerable experience with Jab's locally. Having guides, valves and seats checked for peace of mind. Head looks very good and no signs of being overheated.
What I did find that didn't please me was the intake pipe leaving the plenum. It about fell in my hand when I undid the joiner hose section. Seal on the outside of the plenum was completely lost.
I looked that area over as thorough as one could do on the condition inspection and didn't catch this. Without some disassembly its pretty hard to detect this. It ended up being one of those "ahhah" moments. There was the source of the egt reading at low throttle settings. Probably had some effect at high throttle settings also?
When the head gets done, we'll bolt her back up and do some test flights with the plenum resealed. Hopefully, it will yield positive results and all will be well and good? Keeping my fingers crossed. I've had very few actual issues with this engine. One of the last of the solid lifter models. Mostly just worry about all the issues others have had. I keep on it like a fox. Looking for issues and occasionally finding something like this.

[N111YX]

Thanks, Larry. I have been having one EGT get much hotter than the others. Only at near full throttle though.

[fastj22]

Thanks, Larry. I have been having one EGT get much hotter than the others. Only at near full throttle though.

I had #1 going hot on me. I replaced the rubber tube between the intake box and the intake tube. Solved the issue. I figure it was an air leak making the mixture go lean on that intake.

[DCASonex]

Larry,

My 3300 used to run # 2 hottest and # 6 coolest, until realizing that the spiraling airflow from prop was directing air up and over #2 and piling it up at #6 . I made a modification to top of intake that kept air down on #2 much like on #1 and also rounded off the fins on top leading corner of #2 much as is required for clearance on #1. eliminating the square corner seems to remove some turbulence that robs the air stream of the momentum needed to keep good pressure differential across fins. it is now running nice and cool with #3 and 4 now hottest. Also need to guard against blocking off too much airflow to the cylinder walls when installing the ramp from intake opening to cylinder. I worked some 1/2" scooped holes into mine to direct just a bit of air down around underside of #1 and 2.

A failed experiment by CAMit with a different ring material was informative in that it did show that cylinder wall temperature is important, too hot and oil will loos effectiveness, and that it is hottest near cylinder head. Cylinder wall temperature is not monitored, and problem will only show up as shortened bore and ring life. Also make sure your inter-cylinder baffles are placed under the cylinders as recommended by Sonex and CAMit, not on top of cylinders as originally supplied by Jabiru. If interested, e-mail me for some photos of modified baffles.

David A.

[LarryEWaiex121]

David,

Your observation about the effect of the prop/airflow swirling up and over #2 is something I've read before in passing.
I believe your on to something.
I find it interesting that some of the differences I've monitored over the last 4 yrs seem inconsequential to others.
When I first started flying my plane and got over the initial break-in, I thought 15-20 degrees higher on 2 was bad.
I used to converse with Jim McCormick and he seemed to think I was fussing about nothing. He said most would kill to get even balance on 5 cylinders with only #2 a bit higher.
On long cross country's, I would see the Dynon show balance across all of less than 10 degrees. That made me very happy! Only recently did the balance seem to go away and then I found the intake leak on 2 that I'm fixing now.
Just having the head serviced and checked out due to a considerable degree of caution on my part. I'm really not interested in tossing an exhaust valve over the mtns. here in Idaho.
Thanks for the insight and I'm going to try and implement some of these suggestions.

Larry