[b]Tot:

A little expansion on Jim's comments.

The Thunder Tiger is an excellent engine, made in Free China. It is different from most other engines on the market in that it has a nickel plated liner as opposed to all other good engines of its type that use a chrome plated liner. The result in normal service is no difference, but in a dusty climate it will wear faster than the chromed engines. My son has bought nothing but TT since he got back into the hobby about ten years ago.

The Magnum XLS 46 is an almost perfect copy of the OS 46 FX engine, differing in that the Magnum does have the chrome cylinder, the OS 46 FX had a nickel plated cylinder, which was highly prone to fail, unlike Thunder Tiger which has never had a peeling problem. The Magnum is made in Red China. The Magnum engines have been my choice for sport planes for many years.

The OS 46 AX is a development of the older 46 FX, it is still using a nickel plated cylinder. Giving OS their due, it seems they learned how to do the nickel from Thunder Tiger, they now seldom have a liner failure. Good power, and reliable. I wont spend the money - overpriced in my opinion - but many don't agree.

Summary:

Thunder Tiger. Least expensive, a good engine.
Magnum. Also a good engine, in the same conditions will last some what longer than the TT.
OS. Highest price. For the same money you can buy either of the others and have money left to buy the fuel for a good season's flying. Estimated life similar to the TT because of similar construction.

Bill.