Jabiru3300/Aerocarb Vapor lock?

[builderflyer]

In my installation the Aerocarb sits right behind the oil cooler. Has anyone made a deflector to direct that heat down and out and away from the Aerocarb/Aeroinjector? There is nothing left to insulate. Anyone else had a problem with the starter when it's hot? Next flight I'll check the temp on the Aerocarb right after shut-down. Sorry for the long post, but I know there is a lot of expertise on this forum, and I need some fresh ideas.

Regarding your final questions. First, more than a simple deflector, my Sonex has an aluminum duct mounted at the back of the oil cooler. It dumps the hot air from oil cooler at the exits from cowling which keeps this air from reaching the carburetor or mixing with the hot air from the cylinders inside of the cowling. If you're interested, I can post a photo of this next time I pull the cowling. Second, my 3300 engine is an early version and it came with a black starter motor which is known for its limited cranking power, especially when the engine is hot. If my battery isn't fully charged, my engine won't turn over until it has cooled for a period of time. Once the engine has cooled a bit, the engine will turn over and start just fine.

Hope this helps,

Art,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,Jabiru 3300 #261

[builderflyer]

9SX was finished in 2012 and had only 143 hours on it when I got it. The fuel system is very simple with a bulkhead AN elbow fitting going through the fuel flow sensor and a Jegs Fuel filter. A braided stainless fuel line enclosed in fire sleeve curves slightly downhill to the fuel inlet on the Aerocarb.

You haven't mentioned which of the available fuel flow sensors are in the 9SX system. A fuel flow sensor is a source of pressure drop in the fuel line and can, therefore, contribute to the formation of air bubbles appearing as "burps". The worst offender is the Floscan sensor as at 3300 WOT fuel flow rates, it actually can reduce the fuel pressure to zero given the low head available in the Sonex system. Builders have had better success with one of the "cubes", either the red or gold ones as they have considerably less pressure drop than the Floscan.

My Sonex has the Usher gascolator in its fuel system yet experiences no burps until I add one of the fuel flow sensors. Then, some small burps have occurred under conditions favorable to the formation of air bubbles.

Art,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[BenCharvet]

I've done quite a bit of work since my last post. A buddy in my EAA chapter is building a Onex, and had a new #3 needle for my AeroCarb. The new stainless needles are slightly larger diameter than the original brass one, so I had to take some material off the top with sandpaper to get it to fit in the holder (with no change in diameter of the tapered part). After a few tries I now have the mixture set at a pretty good place. The design of the Aerocarb makes mixture adjustments on mine impossible if you aren't actually looking at the needle while you tighten the locking screw, as it wants to "lean" the mixture. I was able to make the adjustments without removing the mixture or throttle cable, but just removing the carb from the intake plenum and dropping it down to get access. I was surprised that the locking screw was stainless too, and used grease on the allen wrench to hold the screw while installing it. I also added a deflector to direct the hot air from the oil cooler down and away from the carb. I used the design on the link Jeff posted above, and its 14 inches wide and shields the exhaust too. I flew it this morning and didn't have a single burp.

My tachometer readings on the MGL Voyager have been a little suspect at low RPMs, so I added a Tiny-Tach type tachometer that I had on hand. When the MGL is reading 1400-1500 the digital tach is reading closer to 1000 rpm. It appears the MGL RDAC is getting its signal from the left coil, rather than any of the two different style senders shown in the Jabiru manual. I'm wondering if some of my idle problems were just that the idle was set too low. Its idling great now.

I got a great deal on this airplane, and I'm treating it like its still in phase 1, even though it has 150 hrs on it now.

Just for fun I did a full power run at 2500 ft and got 150 mph TAS and 165 IAS. When I get this fully sorted its going to be a blast!