Engine Speed: Portable units run at a fast 3000 RPM / 3600 RPM and are air-cooled. Large industrial units run at a slow, durable 1500 RPM / 1800 RPM and use liquid radiator cooling.Aspiration: Single-cylinder engines are naturally aspirated, while large multi-cylinder commercial models are turbocharged for maximum efficiency.Starting System: Equipped with a 12V or 24V electric key start system paired with a heavy-duty maintenance-free battery.Governor Type: Mechanical or electronic governors that automatically adjust fuel flow to keep the engine speed steady when big appliances turn on.