Carburetor, also spelled carburettor, device for supplying a spark-ignition engine with a mixture of fuel and air. Components of carburetors usually include a storage chamber for liquid fuel, a choke, an idling (or slow-running) jet, a main jet, a venturi-shaped air-flow restriction, and an accelerator pump. The quantity of fuel in the storage chamber is controlled by a valve actuated by a float. The choke, a butterfly valve, reduces the intake of air and allows a fuel-rich charge to be drawn into the cylinders when a cold engine is started. As the engine warms up, the choke is gradually opened either by hand or automatically by heat- and engine-speed-responsive controllers. The fuel flows out of the idling jet into the intake air as a result of reduced pressure near the partially closed throttle valve. The main fuel jet comes into action when the throttle valve is further open. Then the venturi-shaped air-flow restriction creates a reduced pressure for drawing fuel from the main jet into the air stream at a rate related to the air flow so that a nearly constant fuel-air ratio is obtained. The accelerator pump injects fuel into the inlet air when the throttle is opened suddenly.Who invented the carburetor?Carburetors have been around since the late 19th century when they were first developed by automobile pioneer (and Mercedes founder) Karl Benz (1844–1929). There were earlier attempts at "carbureting" in other ways. For example, the French engine pioneer Joseph Étienne Lenoir (1822–1900) originally used a rotating cylinder with sponges attached that dipped into fuel as they turned around, lifting it out of its container and mixing it into the air as they did so. Working Carburetors vary quite a bit in design and complexity. The simplest possible one is essentially a large vertical air pipe above the engine cylinders with a horizontal fuel pipe joined onto one side. As the air flows down the pipe, it has to pass through a narrow kink in the middle, which makes it speed up and causes its pressure to fall. This kinked section is called a venturi. The falling pressure of the air creates a sucking effect that draws air in through the fuel pipe at the side.The air flow pulls in fuel to join it, which is just what we need, but how can we adjust the air-fuel mixture? The carburetor has two swiveling valves above and below the venturi. At the top, there's a valve called the choke that regulates how much air can flow in. If the choke is closed, less air flows down through the pipe and the venturi sucks in more fuel, so the engine gets a fuel-rich mixture. That's handy when the engine is cold, first starting up, and running quite slowly. Beneath the venturi, there's a second valve called the throttle. The more the throttle is open, the more air flows through the carburetor and the more fuel it drags in from the pipe to the side. With more fuel and air flowing in, the engine releases more energy and makes more power and the car goes faster. That's why opening the throttle makes a car accelerate: it's the equivalent of blowing on a campfire to supply more oxygen and make it burn more quickly. The throttle is connected to the accelerator pedal in a car or the throttle on the handlebar of a motorcycle.The fuel inlet to a carburetor is slightly more complex than we've described it so far. Attached to the fuel pipe there's a kind of mini fuel tank called a float-feed chamber (a little tank with a float and valve inside it). As the chamber feeds fuel to the carburetor, the fuel level sinks, and the float falls with it. When the float drops below a certain level, it opens a valve allowing fuel into the chamber to refill it from the main gas tank. Once the chamber is full, the float rises, closes the valve, and the fuel feed switches off again. (The float-feed chamber works a bit like a toilet, with the float effectively doing the same job as the ballcock—the valve that helps a toilet refill with just the right amount of water after you flush. What do car engines and toilets have in common? More than you might have thought!)ProcessIn summary, then, here's how it all works:Air flows into the top of the carburetor from the car's air intake, passing through a filter that cleans it of debris.When the engine is first started, the choke (blue) can be set so it almost blocks the top of the pipe to reduce the amount of air coming in (increasing the fuel content of the mixture entering the cylinders).In the center of the tube, the air is forced through a narrow kink called a venturi. This makes it speed up and causes its pressure to drop.The drop in air pressure creates suction on the fuel pipe (right), drawing in fuel (orange).The throttle (green) is a valve that swivels to open or close the pipe. When the throttle is open, more air and fuel flows to the cylinders so the engine produces more power and the car goes faster.The mixture of air and fuel flows down into the cylinders.Fuel (orange) is supplied from a mini-fuel tank called the float-feed chamber.As the fuel level falls, a float in the chamber falls and opens a valve at the top.When the valve opens, more fuel flows in to replenish the chamber from the main gas tank. This makes the float rise and close the valve again.