Was looking up the cowl exit and gave each pipe a shake. This one was swinging in the breeze. Dropped the cowl and saw it was nearly burned through (wrap was blown away).Wow Toobuilder, good catch !
Did you see a bulge in the header wrap when you got back, or did you remove it for a paranoid post-flight look-see?
This same exhaust gave me no problems for 331 hour prior, and it's been wearing the wrap for the last 10, so it's fairly compelling evidence that the intense heat trapped by the wrap is the root issue. And that sucks, because I'm looking to maximize the heat delta between the exhaust stream and the cowl outflow. It's what makes the ejector work so well. Now I'm going to dump a LOT more BTU's into the lower cowl AND cool/slow down the exhaust velocity.
Flying tomorrow - will report back if there's a change in performance.