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Mixture preparation is a key contributor to both the combustion and emissions in automotive gasoline engines. The air-fuel ratio near the spark plug may have an effect on combustion characteristics since it is related to early flame development. Therefore, cycle resolved measurements of equivalence ratio near the spark plug is particularly important for better understanding of its contribution on combustion and emissions. This paper describes how we determined the in-cylinder equivalence ratio from the measured hydrocarbon concentration near the spark plug using a Fast Response Flame Ionization Detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration.

An experimental study was carried out to develop a new knock-detection method using cylinder pressure, block vibration and sound pressure signals from a spark-ignition (SI) engine. As a first step for knock detection, the 1st, 2nd and 3rd harmonic knock frequencies were determined by analyzing the cylinder pressure signals under a wide range of engine operating conditions. Since these knock frequencies were found to be independent of engine operating conditions and the standard deviations of these knock frequencies were small, three narrow band-pass filters were designed and applied to process the raw signals from the engine. Then a new method, called the Sum of Divided Band-Pass (SDBP) filtering method, was proposed to determine knock intensity, and it was shown to be better than the other methods in terms of knock detection sensitivity and background noise removal. Knock intensity greatly varies with engine operating conditions, knock sensor locations and fuel characteristics, etc.