[Hi5]

Someone told me that when you use forged pistons, the standard knock sensors wont pick up knock due to it happening at a different frequency - is this true?

 

[Hugh Keir]

Hi5,

Detonation does not occur at a single fequency, but is affected by the pressure in the combustion chamber at time of detonation.

The following FFT analysis of a detonating engine shows the knife shaped light blue marks at around 6kHz spread themselves over a range of frequencies.

The forged piston may have a dampening affect on the signal, but will not affect the frequency of knock.

The marks between 2 and 4kHz are just engine noise.

 

[Hi5]

cheers for that, very informative