The following topics concerning knock detection in spark ignition engines are reviewed: reduction of effect of noise on the sensitivity of the measuring instrument; characteristics of the pass-band electronic filter; type and mounting of the transducer; and interpretation of the phenomena as detected and their relation to the energy released from knock and the danger of mechanical damage. In knock detection instruments, background noise always decreases the accuracy of the results. Automatic suppression systems are useful in comparative assessments of different fuels performed at various speeds but are of limited value whenever knock intensity has to be established. Knock detection instruments are generally equipped with an electronic filter for removing the signals relative to the combustion cycle and to noise. Use of too selective filters has its drawbacks. The advantage offered by the use of accelerometers is confirmed by satisfactory experimental results obtained over the last five years. Positioning of the accelerometer over the cylinder head bolts is standard. Results from an accelerometer and a piezoelectric microphone are in good agreement. The mechanism by which knock induces mechanical damage in the combustion chamber is not yet fully clarified. A measure based on the detection of the maximum signal relative to knock for each cycle offers a reasonable indication of the possible mechanical damage which could be expected for a given knock intensity.

  • Supplemental Notes:
    • Presented at the SAE Congress and Exposition, Detroit, 27 February-3 March 1978.
  • Corporate Authors:

    Society of Automotive Engineers (SAE)

    400 Commonwealth Drive
    Warrendale, PA  United States  15096
  • Authors:
    • Arrigoni, V
    • Calvi, G F
    • Gaetani, B
    • Giavazzi, F
    • Zanoni, G F
  • Publication Date: 1978

Media Info

  • Features: References;
  • Pagination: 12 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00395152
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: SAE 780153, HS-025 308U
  • Files: HSL, USDOT
  • Created Date: Jun 30 1985 12:00AM