Assertion: glider's engine | /r/CapableOf | operate on the four-stroke cycle
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text: Glow engines which operate on the four-stroke cycle, whether using ordinary poppet valves or occasionally rotary valves offer superior fuel-efficiency (power-output per fuel-consumption), but deliver less power than two-stroke engines of the same displacement – yet, often because the power they deliver is more suited to turning somewhat larger diameter propellers for lighter weight, more drag-producing airframe designs such as biplanes and scale aircraft models of pre-World War II full-scale subjects, four-stroke model engines, fueled either with methanol or gasoline fuels are slowly increasing in popularity from their generally lower noise output when compared to similar displacement two-stroke engines, and are available (for larger displacement, multi-cylinder four-stroke engines) in opposed twin and radial engine layouts.