<< -ATP web site (http://atpcoinc.com) shows 16.6 GPH at 240 HP
 but they dont describe the test conditions. >>

This would be an SFC of .46 lb./HP/hr.  For reference, .7 to 1.2 are more
typical numbers for small single stage, single shaft, all centrifugal engines
and APU's.  There are a number of well established APU and small turbine
manufacturers who would sell their souls for an SFC of .46!