Signs of detonation?

Help me understand and also coach a young driver for the signs of detonation/pre-ignition?

What engine?

Detonation is caused by an aggressive mix of compression / timing and fuel quality. If you are within the rule set of almost all modern classes in the US detonation shouldn’t ever be a concern as there is a pretty good margin of error in the rules before any of these engines would experience that situation.

Are you running an air cooled engine? Typically it sounds a little bit like a slight dinging noise like you were tapping a screwdriver on the head, but often it’s pretty imperceptible. Like mentioned above, nowadays with the lower performance engines, you would likely feel a drop in power before the engine begins to detonate.

So, probably the best thing to do is have the driver be aware of a lack of power especially pulling out of turns in the mid range. If it feels “flat” it’s probably too lean (assuming chassis is free)

That is my concern. My son and I started in KT100 and now run KA. It seems like ages ago but really was about 5 or 6 years ago. Thinking back I never realized it happening with the KT but I recall a motor builder showing me pitting on the edge of the combustion chamber saying it was from detonation. There was so much racket going on I don’t know if you would hear it either. With the KA I don’t think I have ever experienced it and I haven’t seen evidence but was curious what clues there might be that we could look for. Would EGT temps show it?

Usually engine noises coming from the exhaust pipe will tell you wether there is detonation occuring in your engine. No nosies means no detonation