How to detect Detonation without knock sensors? I have knock sensors but I need to tune them. In a car I can easily hear it in a twin engine boat....not at all. Any ideas you guys have tried?

The real way is to use in cylinder pressure transducers and an extremely high sample rate DAQ to measure cylinder pressure as a function of crank angle. However, that is not likely in the budget unless you are an OEM. And if it is in the budget we need to become friends and we can build a kick ass engine test cell...lol

Other ways are inspecting plugs (black flakes), detonation muffs (google det cans), and there are some accelerometers/microphones that claim to detect detonation (one example below). However, without knowing (or being able to determine) the natural frequency of your engine assembly I am a bit skeptical on their accuracy without knowing the "window" of frequencies they are looking for.

Some have claimed to intentionally induce knock (audible to the ear or det cans) while datalogging their knock sensor. This would at least alert you of "hard" severe knock.

https://thetuningschool.com/products...=7176861220925

https://www.plex-tuning.com/products...knock-monitor/

and there is other companies whom have Knock detection lites

If you're handy with the soldering iron, you can build a stand-alone knock sensor warning light/buzzer yourself based off a 555 timer. You'll still need the appropriate knock sensor for your eng.
I built one many years ago when tuning my fuel injected Camaro eng. It worked well once you get it adjusted for your sensor/eng. I debated building 2 more for the boat but never got around to it.
I can't post images here, but if you're interested, PM me your email and I can send the pics to you.

You can post images now. Only requirement is 10 posts. The man finally removed that terrible rule.

Good deal on posting pics. Thx!
Here's the schematic


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Once I had all the parts, it took maybe 2 hrs to assemble and abt 1 more hour to install the dedicated knock sensor, route wiring and mount the box. Seems like the parts costs maybe $20, but that was almost 20 years ago. There's nothing really special about any of the parts. I bought them all at Radio Shack. The parts list references Radio Shack part numbers which I can post if wanted.