<P> When carburetors are used in aircraft with piston engines, special designs and features are needed to prevent fuel starvation during inverted flight . Later engines used an early form of fuel injection known as a pressure carburetor . </P> <P> Most production carbureted engines, as opposed to fuel - injected, have a single carburetor and a matching intake manifold that divides and transports the air fuel mixture to the intake valves, though some engines (like motorcycle engines) use multiple carburetors on split heads . Multiple carburetor engines were also common enhancements for modifying engines in the USA from the 1950s to mid-1960s, as well as during the following decade of high - performance muscle cars, fueling different chambers of the engine's intake manifold . </P> <P> Older engines used updraft carburetors, where the air enters from below the carburetor and exits through the top . This had the advantage of never flooding the engine, as any liquid fuel droplets would fall out of the carburetor instead of into the intake manifold; it also lent itself to use of an oil bath air cleaner, where a pool of oil below a mesh element below the carburetor is sucked up into the mesh and the air is drawn through the oil - covered mesh; this was an effective system in a time when paper air filters did not exist . </P> <P> Beginning in the late 1930s, downdraft carburetors were the most popular type for automotive use in the United States . In Europe, the sidedraft carburetors replaced downdraft as free space in the engine bay decreased and the use of the SU - type carburetor (and similar units from other manufacturers) increased . Some small propeller - driven aircraft engines still use the updraft carburetor design . </P>

What is the function of the venturi in a carburetor