Carburetors are complicated mechanical contrivances, and can be difficult to understand for the uninitiated. They’re often explained with teaching resources like cutaway drawings and diagrams that reveal the magic going on inside. Even better would be to look inside as it’s all happening, and with the transparent carburetor from YouTuber Smarter Every Day, you can do just that.
The video came about when Destin Sandlin, the man behind the channel, asked his father to explain to him how carburetors work in practice. This inspired him to build a transparent carburetor so that he could literally see what was happening inside. The device was built using a transparent resin 3D-printed housing for the bowl and venturi, and fitted with a float and needle from a Briggs and Stratton carburetor. Throttle and choke were then installed, made from 3D-printed PLA plastic. The clear carb was then installed on a small single-cylinder engine on a Craftsman garden tiller.
The principle of operation is simple. Fuel from the tank flows into the bowl, raising the level of the float as it does so. As the fuel in the bowl gets higher, the float does too, until it closes the needle valve which stops further fuel flowing into the chamber. This mechanism maintains the right level in the bowl as fuel is consumed by the engine. Atop the bowl sits the venturi tube, connected to the intake of the engine. As air is sucked in through the venturi by the engine’s intake stroke, it creates a vacuum, which sucks fuel from the bowl into the venturi tube via a small hole called a jet. It’s by this process that the fuel is mixed with the incoming air, to create the combustible mixture that then burns in the cylinder on the power stroke.
The slow-motion footage shot by Sandlin does an amazing job of illustrating exactly how everything happens in a real working carburetor. Fuel can be seen to gradually flow into the venturi, before the droplets are atomized by the rapid suction of the engine’s intake stroke. It’s also possible to see the vortexes formed behind the throttle plate, and the vibrations of the engine’s four strokes, which shake the fuel in the bowl in a mesmerizing fashion.
It’s the best education in carburetor operation you could possibly ask for, and it’s beautiful to see those droplets of fuel traveling through the intake on their way to make power. It’s a great companion piece to Sandlin’s previous work, showing what happens inside an engine’s combustion chamber. We’ve also been lucky enough to see what goes on in the intake of a turbo Toyota Supra. Sometimes, there’s no better way to learn than by simply seeing the basic principles in action.
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