ORIGINAL: beppeVRCS


For what is worth, this has been my experience:
I've been using a Goldberg Tiger 60 to test some .60 size engines, with an APC 12''x6'' propeller.

.60-.61 Engines Comparative Tests.
Fuel 10% Nitro. 21% Mixed Synt./Castor Oil

Engine Date Propeller RPM
Supertigre G-60 7 July 2006 APC 12x6 10.900
Supertigre X-60 4 Sept. 2006 APC 12x6 11.250
MDS 61 29 Sept. 2006 APC 12x6 10.800
O.S. FX-61 8 October 2006 APC 12x6 11.750
Supertigre S-61K
Old Muffler 15 October 2006 APC 12x6 11.700
Supertigre S-61K
New Muffler
29 October 2006 APC 12x6 11.700
KRAFT 61 18 March 2007 APC 12x6 11.800
MAGNUM XL .61 29 April 2007 APC 12x6 11.750
Magnum + T.T. Sil.19 May 2007 APC 12x6 11.850
Thund. T. GP-61 15 July 2007 APC 12x6 11.550
Thun. T. PRO-61 21 July 2007 APC 12x6 11.800
HP .61. (1975) 29 July 2007 APC 12x6 9.990

Engines were not tested all under the same atmospheric conditions, and over almost an year; nevertheless the KRAFT 61 is among the strongest of the group. It was consistent in flight, with no bad habits, good idle, smooth transition. In my opinion it is still competitive today, as a sport .60, at a very low price.
Ciao
Beppe