May be a re post?? but I wonder how this was filmed?

LINK

Typical you tube video in that it's an interesting video with the square root of feck-all detail provided.

I'm guessing it has been done with a strobe or something.

Easy, use something like an Alfa twinSpark and chuck a camera/probe down and make it a singlespark. Doesn't have a very steady hand though

ATB

Simon

It's done using a transparent cylinder made from symthetic sapphire. Cost in the region of £25K each, as off a few years ago.
I saw a film of Shell doing this, using a high speed camera, to track flame front developement and progress, across the combustion chamber.
They had a sapphire cylinder with a single cylinder head specially made by Ferrari. They use it to develope fuel additives for Ferrari that comply with F1 rules.