There has been a lot of interest shown in "under $55" class engines. This calls for testing of two engines that is very objective meaning that the tests are not based on any agenda other than to decide which engine proves to be the best value. "Pride of ownership" bias is nullified since both engines are owned. The engines being tested and compared are the OS-40FP ($54.95) and the Thunder Tiger GP40 ($49.95).

Since weight, appearance, quality of materials, etc. are nearly identical, the descriptive info will skipped but a few things should be mentioned. The OS needle valve bubbled fuel at high RPM and the front bushing spewed fuel. The TT features a nice drawbar type clamp for the carburettor while OS has a twin machine screw method that prevents substituting any other carb. Also, the TT has true ABC and will last longer and take abuse better.

At the time of testing, the OS-40FP had had about a gallon of fuel run through it and the TT GP40 had only had one 12 oz. tank run through it. Proper break-in procedure had been followed for both engines.

Testing was performed using the stock mufflers and a 13.5 inch mousse can pipe for comparison. A 10x6 prop was not available at the time of testing but tests were performed using the same props on both engines. The fuel used was Red Max 10% with 10% castor and 7% synthetic. Glo-plugs used were McCoy #59 and OS #8 with equal results so this was discounted.

The figures resulting from using the MCP are pretty impressive for engines costing under $55 and weighing a very light 8.8 ounces. A 10x5 prop turning 13900 RPM generates enough thrust to pull a 5 pound trainer with authority. This prop turning 12800 however, is marginal for a 5 pounder.

The figures for objective scoring are based on personal impression only based on the outcome of comparing the engines.

It appears that the results are overwhelmingly in favor of the TT, and objectively they are but it must be pointed out that the OS is very close in comparison.