CHT on #5 3300

[Sonex-1081]

Just adding my results here....I have the Jab 3300 with an Aeroinjector and 'under the plug ring type' CHT sensors to an MGL iEFIS. I have clocked up 16 hours. OAT is generally 25-32deg C (damn HOT). My installation is almost exactly as per the Sonex baffle kit instruction book and I consistently have #1 as the hottest cylinder running at about 160 degC with #3 #5 both at 150degC. #'s 2,4 & 6 all run much cooler at 125-133 degC with #4 being the coolest. I tried trimming the front baffle plate on the Right Hand Side and drilling a couple of holes in it to get more direct cool air on #1 but no real result from that. I also have the nose gear version (with offset leg on Left side) and I run mine without the cover plate that wraps around where the gear leg exists the cowl.....This means the LHS cowling outlet area is a fair bit larger than the RHS. I'm not sure whether this is the cause of the LH/RH side temp spread. I think I will try installing the cover plate to reduce outlet size on LHS and see what happens. Any ideas for a more even spread would be great.

[DCASonex]

Sonex 1081: Your CHTs are sufficiently different from most that I would double check that your sensors are reading the cylinders you think they are.

David A. CAMit 3300 in Sonex TD

[LarryEWaiex121]

Sonex 1081,

Along the lines of what David just mentioned, I'd make darn sure your seeing what your seeing. By that I mean pull the plugs and run around the engine one plug a time with a propane torch and lightly wick each one and have someone sit in the plane and call out the cylinder# and confirm your numbering order on the sensor's. If your 100% convinced they are correct then you have to start from there.
On my Jabiru 3300, # 2 was always the warmest over a variety of flight conditions, #1 was mostly the coolest, #5 and 6 in the rear were consistently the most stable. Number 3 and 4 in the middle normally split the difference between the front and rear holes.
I completely resisted the theory that the under plug thermocouples could be at fault but I found out different. I experimented with tighting the plug and working diligently with getting the sensor centered and it changed my readings on the high reading holes by as much as 30 degrees F and convinced me there can be significant error just in the instrumentation based on your install.
Quite honestly, getting back to your particular setup, you don't have enough time yet to have a broken in engine. Obviously you don't want to bake your engine but, your readings will all come down after about 30-50 hrs. It takes that long for things to settle in.
Till then I would make certain mixture is adequate(plug color), temps are in bounds and oil is at no more than mid level. Anything more then mid stick on the oil will make the whole engine hotter. Good luck.

Larry
Waiex121YX