Even at 55V it makes a pretty big zap, so 300V is a lot. I might not release this one to the Speeduino forum if I get it working because parts aren’t easy to find, but I still have to make a compact one that I’m going to mount on the car and try to film the ignition advance curve as I drive around because I want to get an idea of what the factory ECU ignition curve looks like.
EDIT - I just realise it might not work because the energy released from the flash interferes with cameras.