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A new low cost, quick responding, and compact NOx sensor using ZrO2 thick film and the meter have been developed. The sensor is amperometric and consists of two cells: the first cell is an oxygen pumping cell; the second cell is also oxygen pumping cell extracting oxygen from NOx by dissociating it into O2 and N2 gas. The oxygen pumping current in the second cell is proportional to the NOx gas concentration in the second cell and the exhaust gas. The meter is small size, light weight and can measure NOx and A/F ratio at the same time. An unique electronic algorithm is also developed to optimize the electrochemical control system effectively.

The corelation between flame ion density and engine operating condition, such as air fuel ratio mixture and cylinder pressure peak value, etc., is commonly known. However, due to the difficulty of ion probe installation in the engine and the interruption of the high voltage ignition spark, the ionization current method is not optimally utilized. This paper presents the Spark Plug Voltage-ion method which requires a minor modification to the ignition system and will indirectly detect flame ion density. The voltage sensor is a voltage divider by capacitance which measures the spark plug voltage. The resulting behavior of the voltage wave form is noteworthy. After spark discharge, the stored residual charge of the spark plug starts to discharge by ion in a flame. Therefore, ion density in a flame is detected by the decay time of spark plug voltage.

The basic characteristics of the TiO2 sensor were introduced on a previous SAE paper which was submitted by NGK Spark Plug Co., Ltd. and further discussed on several other papers which have also been recently published. This paper will describe the effect of a precious metal catalyst on vehicle emissions. Emphasis is placed on the effect of the distribution of the precious metal catalyst in the titania element which significantly affects the reaction among unburned components in the exhaust gas as well as sensor performance. The relationship between the catalyst distribution in the sensor element, and the closed loop emission results, including test variability, will also be discussed in this paper.

The idea to monitor the combustion in an internal combustion engine and using the obtained data to control combustion in the engine has been around for some time now. There are two well-known methods, although in the capacity of lab experiments, which had been developed under this principle. One features the analysis of combustion pressure and the other features the analysis of ionic currents detected in the combustion gas. Although highly precise analysis can be achieved by the former, there are problems in the installation of sensors for detecting combustion pressure, also in the durability and cost of such sensors. As for the latter, there are also problems in installing sensors for detecting the ionic currents and the reliability of obtained data from such sensors is still questionable.