I meant 'engineered to avoid detonation'

Detonation can be caused by either excessive temperature or excessive pressure of the fuel-air charge. Take that for granted - but how can you engineer a motor not to det' if you can't actually detect when you have reached the point of detonation? I mean you can obvioulsy ensure that cylinder head temp's etc are kept within tolerance, but if you cannot detect it, you don't know what the tolerances are....