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This paper presents the application of fuzzy expert system technique as a basis to estimate ignition timing for subsequent tuning of a Toyota Corolla 4 cylinder, 1.8l hydrogen powered car. Ignition timing prediction is a typical problem to which decision support fuzzy system can be used. Based on extensive experiments, the basic fuzzy rules on ignition timing have been constructed, in which the engine speed, throttle position, manifold air pressure, fuel pulse width, engine power, lambda value were chosen as fuzzy sets of the linguistic input variables, and ignition advance is selected as performance output of the fuzzy system. The constructed fuzzy system initially mapped 136 basic rules based on physical theories and extensive experimentation. For all the input parameters various triangular, trapezoidal and generalized bell-shaped membership functions were successfully applied to best represent the ignition timing output from the expert system. The results have shown that the minimum ignition advance for maximum torque without detonation was achieved. The estimation of ignition advance achieved from fuzzy expert system was ± 5% root mean square error. [ABSTRACT FROM AUTHOR]