I have a friend with a dyno set up for aircraft engines. Can’t get into what he does, but he has in-cylinder high speed transducers for setting timing curves at “lean of peak” on lyco engs. Very neat to be able to visualize knock coming in. These are very expensive spark plugs!
The sensors are some of the fastest reacting, yet still are only accurate at lower engine speeds(fine for prop aircraft engines)
The spark plug transducers definitely have accuracy issues at higher engine speeds. There are also transducers available that are designed to be installed in specially machined cylinder heads, those are accurate at higher rpm than the spark plug versions. It's really awesome technology, but it's usually into the hundreds of thousands of dollars range to get an engine set up with it.
https://www.kistler.com/en/applications/...essure-testing/https://www.avl.com/-/all-in-one-indicating-systems
