Your slow-motion video guide to how a carburettor works

by Antony Ingram
2 July 2021 2 min read
Your slow-motion video guide to how a carburettor works
Photo: Smarter Every Day

Have you ever stopped to consider how a carburettor works? If you’ve ever stripped a carb down when working on your car you’ll probably have a pretty good knowledge, but it’s unlikely you’ve ever seen the inner workings of one, because generally if it’s working, it’s one of those components you don’t really give much thought.

That’s what makes this video by Smarter Every Day so fascinating, because host Destin Sandlin doesn’t just explain how a carburettor works: he has one built out of transparent materials, and then films every part of the process in slow motion.

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If you’re not familiar with Smarter Every Day, it’s essentially a YouTube channel dedicated to discovering what makes the world tick. In the past, Sandlin has filmed a flathead single-cylinder engine in slow motion too, observing how the fuel mixture is drawn into the cylinder, compressed and combusted, and pushed through the exhaust valve – all through a transparent cylinder head.

Sandlin’s latest video came about through watching his father fix the carburettor on some garden equipment, and after a fascinating lesson on the inner workings, decided to explore the component in a way nobody else has tried before.

The result is just about the simplest carburettor it’s possible to build, with a 3D-printed venturi and float bowl assembly, the float from an aftermarket carb, and simple (also 3D-printed) choke and throttle butterflies.

It might be rudimentary, but with solid science behind it, the see-through carb actually works pretty well, comfortably powering the small engine it’s attached to, though Sandlin and his father quickly realise the engine is easier to choke with a well-placed thumb.

The footage, though, is amazing. We see the action from several vantage points, observing small bubbles of fuel getting sucked up through the jet and turned into vapour during the intake stroke, the effects the engine’s vibration has on the fuel in the bowl, and then a view down the venturi itself.

The tiny plastic butterflies eventually buckle due to the warmth of the lights used to expose the slow-mo footage, but in just a few frames, the video makes the operation of a carburettor clearer than it’s ever been – literally. From the images, it’s easy to see how changing the way a carb operates – by installing different jets, or admitting more air with a larger throttle butterfly – will affect its operation.

So next time you go for a drive in your classic, you’ll know exactly what’s happening under the bonnet – and perhaps have even more respect for the remarkable piece of technology that is the humble carburettor.

Also read

How engineer Beatrice Shilling saved the Spitfire
Shift Happens: The High Carb Diet
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