Heat measuring system for detecting knock in internal combustion engine

In an internal combustion engine having an engine cylinder defining a combustion chamber:

• pressure detecting means for monitoring fluctuations in pressure within the combustion chamber of the engine cylinder of the internal combustion engine and generating a first signal indicative of said monitored fluctuations;
• removing means for removing high-frequency components having frequencies higher than a predetermined cut-off frequency from said first signal and generating a second signal, wherein said high-frequency components from said first signal are removed;
• running condition detecting means for monitoring a running condition of the internal combustion engine and generating a third signal indicative of said monitored running condition;
• total heat quantity computing means for deriving a total heat quantity produced in every engine cycle, on the basis of said second and third signals;
• knock heat quantity computing means for deriving a knock heat quantity generated in every engine cycle, on the basis of said second and third signals;
• knock intensity determining means for determining knock intensity on the basis of a predetermined relationship between said knock heat quantity and said total heat quantity and generating an output signal indicative of said determined knock intensity;
• means for generating an ignition control signal on the basis of said output signal;
• and
• means, including a spark plug, for generating an electric discharge in response to said ignition control signal.