Bobby,

You are to be commended for getting down safely and for proceeding with caution afterward.

I did some exhaust back pressure tests with my engine stand which is a NA 13B.  Increasing the exhaust back pressure was accomplished by partially blocking the outlet.  An increase in back pressure from 23” to 34” of Hg resulted in about a 20% decrease in HP.  The thing that was interesting is how small the outlet was when the HP decreased by that 20%.  I didn’t measure it, but it was less than one square inch.  I would expect that blocking off more of that small remaining area would have had a dramatic effect.  I can test the effect of more completely blocking off the outlet with the engine stand if it would be of interest to you.  It will take something more substantial than a banana to do the job, though  ;>) 

During an extended below zero cold spell here, I had a friend who had his muffler completely fill with ice because of driving to work and back just a short distance.  After the muffler was completely blocked, the engine would start, run for a second or two, and the die.  He had the car towed to the dealership and warming it up in the heated repair shop fixed the problem.

Steve

It’s supercharged. My EGT’s never get over 1540F. Most of the time they run in the 1400’s. I am also not 100% convinced the muffler was to blame. But it seems to fit the symptoms. I can’t confirm the muffler was blocked after landing while trying to taxi. One theory is the exhaust pressure was enough to keep all the little pieces in place until after shutdown. Then towing the plane shook everything loose. Wonder if I could talk Mark S. into sticking a banana in the tail pipe on a full power ground run to duplicate the problem? This is my second HP-2 muffler in about 100 hours of engine time. It may have 25 hours of flight time. The first one was inside the cowl and angled down and back. It lost all the mesh and cone material. The angle may have helped some of the loose material exit the muffler. But it’s all speculation.

Bobby