Torsional crank twist

[Holmz]

Not entirely a MoTeC project...

Been looking at torsional crank twist for one engine, and not got side tracked doing the same for a different engine.

Are there any tell tale signs between misfire and detonation in gas (LPG/CNG) engines?

There is no lambda on the engine or I would probably start with lambda for misfire.
There is also no knock sensor, nor is there likely an easy way to get one on. Plus the engine is noisy to begin with.

I do have crank trigger data sampled with a sound card and that has a lot of harmonics at the engine speed and harmonic of the engine speed.

Are there some easy clues in the engine RPM or crank phase?

[AdamW]

Are there any tell tale signs between misfire and detonation in gas (LPG/CNG) engines?

You would see the same signs of detonation as with any other fuel. Early signs of detonation would be aluminium or black specks on the spark plug ceramic.

There is also no knock sensor, nor is there likely an easy way to get one on. Plus the engine is noisy to begin with

There must be somewhere you can attach a knock sensor for audio monitoring - I have hung them off intake manifold studs and engine mount studs etc with good success.

Although Im sure looking at crank acceleration you might be able to see a misfire or det event I very much doubt you would be able to see any difference between the two especially with such basic acquisition equipment.