Four-Stroke Engines: Market Overview

The internal combustion engine exerts an enormous fascination on many model aircraft enthusiasts—a fascination that is often inexplicable and has an almost magical quality. For this reason, the die-hard engine enthusiast will never consider replacing the internal combustion engine with an electric motor. On the other hand, the relatively high-revving two-stroke engine—which is difficult to dampen—will be replaced by the more trouble-free and environmentally friendly four-stroke engine, particularly in applications where peak performance is not required. Many model flying clubs have already switched entirely to four-stroke engines in recent years, and most will (have to) follow suit in the near future.

The four-stroke engine is a genuine alternative and is suitable for most model designs. The often-criticized screeching noise is completely eliminated, and there is no need for elaborate muffler designs such as resonance tubes and the like. Most four-stroke engines are equipped with only a narrow exhaust tube instead of a muffler, which is sufficient for now but leaves room for additional muffling options in the future.

Since more fuel residue remains in the engine crankcase than with a two-stroke engine, oxidation could occur if low-quality oil is used. Therefore, attention must be paid to oil quality—but that is a matter of cost. Whether I use oil that costs two to four francs per kilogram or one that costs seven to ten francs is bound to make a difference somewhere. This is likely to affect the total cost of fuel as well: If you skimp here, you’re skimping in the wrong place! In addition, a four-stroke engine uses a fraction of the fuel that a two-stroke engine consumes.

Below, we present the most common four-stroke engines available today. The technical specifications are based on information provided by the manufacturers and have not been verified by the editorial staff. The very attractive KALT four-stroke engine we previously featured is not included in this overview, as the Japanese manufacturer has temporarily suspended production of this engine due to excessively high production costs. However, research at KALT continues intensively.

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Yes, 35

O.S. 40

O.S. 120
Gemini

Saito 80 Twin

O.S. 60

Page 40

Yes, 40

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