Exhaust tunnel clearance

[wingnut99]

Has anyone had problems getting their generation 4 Jabiru 3300 exhaust pipes to clear the front of the exhaust tunnels? Mine were barely clearing until I installed the cooling baffles and now I have to work the cowling inlets into the baffling flanges as I'm raising the rear of the lower cowl into place and the exhaust pipes, especially the passenger side is hitting the top of the aluminum tunnel about a 1 1/2" behind the front of the tunnel. I can do surgery on the tunnels if that's what's required but I could have located them further back on the cowl had I known ahead of time.

[WilliamBatten]

Can you send a few pictures - to help those of us who are earlier in our build. Looks like a good learning opportunity.

Thanks,

Bill

[wingnut99]

Hopefully these upload. As you can see the pipes extend into the tunnels, particularly the right one. What I've done at this point is remove the pipes and install the lower cowl then insert them down into the tunnels and slide them onto the headers. It's pretty tough getting the springs on that way but it worked. I may try to trim the baffle inlets enough to allow the nose of the cowling to swing straight up after the pipes are inside the tunnels but I'm not optimistic that it will work. Just hoping someone else had experienced this issue and found a simple solution.

[racaldwell]

Well, if you want to spend a week making an adjustable cowl flap, then your problem disappears. Mine was modeled 3D in Inventor and all fit except I didn't account for the slant of the firewall. I had to redesign the mounting for the actuating lever. The cowl flap gives a 12% improvement in L/D with it closed vs. open. I'm sure the much faster Waiex could have some exit area closed during cruise to reduce drag.

I can share pictures but there are some already posted to this forum and on my EAA Builders Log. But here are a couple to give you an idea.

Cowl Flap Rt Side Mounting Sm.jpg (157.44 KiB) Viewed 1199 times

Cowl Flap Finished Sm.jpg (137.5 KiB) Viewed 1199 times

Cowl Flap Closed Front Sm.jpg (198.95 KiB) Viewed 1199 times

Rick Caldwell
Xenos 0057 49 hrs
Camit 3300