Thanks for the report. Did you get a chance to compare 'em at the RPM in which we'd expect to run them in an aircraft (about 4500 to 6000 RPM)? Same thing? I'd expected the 3 cyl to be more shaky than the 4, just due to the fewer torque pulses and the inherent rocking couple of an inline triple that an inline 4 doesn't have.The difference between the 3 cylinder and the 4 cylinder for vibration and smoothness is night and day, and the ChangAn is now sitting in my factory.
The "pros" of the AM10 for many folks will be the very good HP/lb, the very good HP/$ (especially since the elevated thrust line of the AM10 PSRU will allow users to avoid the higher costs of the laid-down inline versions). Good BSFC too, compared to an air cooled alternative. More vibe is maybe the price for that.
I suppose Mark K has looked at using a similar offset PSRU to raise the thrust line on the AM13 and AM15 rather than lay the engine down (which increases the price by $2000). The offset PSRU of the AM10 is rated for 120 HP, so big enough to handle the baseline output of the AM13 (100 hp) or the AM15 (117 hp).