New Super Slo-Mo Footage Captured the Combustion Process Inside a Transparent Engine

Get ready for an explosive reaction, in 4K video.
Chris Young

Though countries worldwide are starting to gradually phase out the production of internal combustion engine vehicles, the four-stroke engine has to be given credit for being an incredibly reliable machine for over a century.

Now, thanks to a video on YouTube channel TROdesigns, brought to our attention by The Driveyou can see the process inside one of the engine types that has powered transportation for decades.

An acrylic cylinder as a window into the combustion process

The people at TROdesigns took a 1977 Honda XR76 engine and replaced its metal cylinder with a see-through version made out of acrylic so that they could record the combustion process using a 4K resolution high-speed camera.

Of course, acrylic isn't really suited for the intense heat of the combustion process. That's why they also lengthened the cylinder to lower the compression ratio of the engine — the ratio between the volume of the cylinder and combustion chamber — from 9.5:1 to 8.7:1, to allow the engine to run for a longer period before destroying itself. By doing this, they gave themselves enough time to capture the footage they needed. The piston was also polished and custom piston rings were added to help prevent breakage.

Internal combustion engines are being phased out in slow motion

The video (embedded above) shows the machining of the piston rings as well as the assembly of the engine before showing the engine in motion at around the 13-minute mark. The crisp video footage shows the valve gear and piston moving together in slow-motion as well as flames inside the surprisingly robust acrylic cylinder as the combustion process takes place. It's impressive stuff, and it might be the most detailed video footage of an engine we've seen since a group of engineers adapted a diesel engine to run on gasoline.

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The clip is pretty mesmerizing, from the movement of the piston in slow-motion viewed from different angles to the sound of the engine as the adapted piston moves in real-time. And the acrylic cylinder also looks surprisingly durable, as the inside of the engine is still clearly visible even after running for quite some time. With countries like Canada and Norway announcing a ban on internal combustion engine vehicles, to come into effect in the 2030s, this footage could form part of a museum or art installation in the future. It feels like an impressive testament to the decades-long staying power of the internal combustion engine throughout the 20th century. Though we wouldn't suggest fitting one of these things to your motorbike.

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