George,
I revisited the issue with Don Goetz and Gene Hughes on the phone today.
Both know the problem.  Don has flown as much as anyone out there, and Gene
has had his 4P flying a long time.  Don insists its the cowl air coupled
with the restricted air intake when the alternate air system is the only air
intake.  In order to do the proper test you'd have to plug the ram air
induction and only use the alternate air door for intake.  I believe the
twists and turns of that system coupled with hot cowl air coupled with no
ram air simply does not work well.  Gene reaffirmed my experience, in ice
its full rich and 20" MP to keep CHT's under 420.  There may be some
difference with different baffling and how much stuff is restricting air
flow within the cowl.  

With no air cleaner it would take more ice to plug things up.  That filter
is quick to clog with ice.  Don thought his plane worked better than most
because there were gaps around his filter, so when the filter iced up he had
some flow around the edges.  Not quite the system one wants for clean air
intake, but better in ice.

To your credit things work greatly better with GAMI injectors.

But trust me, you engineers out there, it is a problem.

Larry Klaas
2625 NW Ordway Ave
Bend, OR 97701-5497
Tel: 541-388-2420  Fax: 413-581-0178
Email: LDK@bendcable.com