I have run both the AMT-280, 280-SP and Pegasus HP in my BVM F-4 (with bypass) and I am now running the 280-SP on my KingCat. Can't say that I have ever noticed any difference in spool up in any of the configurations. The AMTs fit snuggly in the bypass but that really shouldn't make any difference as long as there is adequate air flow into the compressor. You could try running the engine without the bypass cover on and that would surely allow more than enough air.

Since it is a brand new engine I suspect the issue has to do with something else. Ideal sitution would be to run it on a test stand or even on your KC so as to eliminate variables but I know what a pain it is to do that.


Craig