Measurement of the Extent of Abnormal Combustion by Means of an External Device

The detection of cyclic dispersion, knocking, preignition, misfiring and other phenomena related with abnormal combustion in spark ignition engines has been extensively studied in the past. The transducers most commonly used detect pressure and/or ionization in the combustion chamber.

By employing transducers that detect engine head movement it has been possible to examine these phenomena without particular engine modifications, thus enabling measurements to be made in commercial cars. These transducers are used in conjunction with electronic apparatus that gives quantitative measurements of the extent of the abnormal combustion.

Results obtained by these means are reported with particular emphasis on high speed knock (a problem presently encountered with European cars), preignition and misfiring. On the basis of the test results a technique is developed utilizing the electron scanning microscope to recognize a posteriori if the piston failure is due to knock or preignition.