ottomoottorit

Ottomoottorit, or Otto engines, are a class of internal combustion engines that operate on the Otto cycle, typically four-stroke spark-ignition engines. They are named after Nikolaus Otto, whose development of a practical gasoline engine in the 1870s and 1880s helped establish a standard engine type for automobiles. The term is used in Finnish-language sources to refer to these engines.

Principle and cycle: The four-stroke sequence comprises intake, compression, power, and exhaust. During intake, the piston draws air or an air-fuel mixture into the cylinder; during compression, the mixture is compressed. Near top dead center, the spark plug ignites the mixture, causing rapid expansion that drives the piston (power stroke). The exhaust stroke then expels spent gases. In practice, engines approximate the ideal Otto cycle, with real-world losses from heat transfer and friction.

Design and variants: Otto engines come in inline, V, or other configurations with three to many cylinders. They typically use overhead valves or camshafts, and in modern practice, turbocharging, direct fuel injection, and variable valve timing to improve efficiency and power. They rely on spark ignition, unlike diesel engines that use compression ignition. Emissions controls, such as catalytic converters and exhaust gas recirculation, are common.

Applications and impact: Otto engines have long been the dominant powerplant for automobiles and motorcycles and have seen use in light aircraft and various machinery. They remain widespread, though hybridization and electric propulsion are reducing their share in new vehicles. Efficiency depends on compression ratio and air-fuel management; modern gasoline engines typically achieve practical thermal efficiencies in the 30–40% range, with ongoing improvements through materials, fueling precision, and control technologies.