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In-cylinder pressure of an IC engine is considered to be a major source of information about combustion process. It is a generally accepted method to obtain an in-cylinder pressure signal using a pressure sensor (transducer). In this paper, a different approach is presented. Information about the in-cylinder pressure can be obtained by measuring breakdown voltage across the spark-plug gap. A simple means for measurement of such voltage is developed. The breakdown voltage threshold depends on the density of the gas in the combustion chamber. A strong correlation between the measured breakdown voltages and in-cylinder pressure has been established.

Recent advanced technologies in diesel engine FIE(Fuel Injection Equipment) allow high pressure and multiple injection to be used to reduce particulate emissions without significant penalty in NOx emission. It is also well known that diesel engine particulate matter(PM) and NOx emissions can be reduced by the exact injection rate control according to engine conditions. This study was conducted based on such engine conditions as engine speed, load, swirl ratio and solenoid pulse timing and duration. The fast solenoid valve was installed between the connecting part of nozzle and fuel line. The ball valve driven by solenoid is open after the controller generates pulse and it spills the high pressure fuel in the high pressure nozzle chamber. Fuel line pressure, injection rate, cylinder pressure and exhaust emissions were measured with the variation of control method(pulse timing and pulse duration period).