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In this work, the effects of engine operational parameters, λ, spark timing, and compression ratio, on knock tendency and intensity as well as H2 supplementation are studied. We postulated, verified and eventually used the duration from ignition to 70% mass fraction burnt (MFB0-70%) as an explanatory variable to describe the knock tendency and intensity. In this manner, the physical factors and fuel factors that are introduced by the differences in test conditions can be differentiated. Practically, in terms of percentage of knocking cycles or the spark timing at audible knock, knock tendency decreases as λ increases and increases with H2 supplementation. However, when MFB duration is taken into account, then for the same MFB duration, knock tendency increases as λ increases and decreases with H2 supplementation.

Exhaust gas temperatures in a 1.4 L, sparked ignition engine have been measured using fine wire thermocouples at different loads and speeds. However the thermocouples are not fast enough to resolve the rapid change in exhaust temperature. This paper discusses a new thermocouple compensation technique to resolve the cycle-by-cycle variations in exhaust temperature by segmentation. Simulation results show that the technique can find the lower time constants during blowdown, reducing the bias from 28 to 4%. Several estimators and model structures have been compared. The best one is the difference equation-least squares technique, which has the combined error between -4.4 to 7.6% at 60 dB signal-to-noise ratio. The compensated temperatures have been compared against combustion parameters on a cycle-by-cycle basis. The results show that the cycle-by-cycle variations of the exhaust temperatures and combustion are correlated.