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As specific engine power output increases so does the heat rejected to the coolant. The resulting need to increase radiator size is counter-productive due to the lack of package space, and a strong desire to reduce, not increase, vehicle drag. Current tendency is to size the radiator to reject sufficient heat at extreme operating conditions (full engine power, high ambient). However, this “oversized” cooling system may only be needed by a small number of vehicles. A better approach could be to size the radiator for the majority, but not all, operational conditions and manage the coolant temperature by actively controlling coolant flow and engine output. This will need to be done without compromising durability or driveability. This approach sounds highly beneficial in principle, but how sound would it be in practice ? The authors have investigated the feasibility of active control by considering the details of radiator performance and engine heat rejection.

The Rassweiler and Withrow method for determining mass fraction burnt from S.I. engine cylinder pressure data is widely used, but implementation details vary. The best form of implementation, and the effect of uncertainties in the assumptions made, have been investigated. Attention has been given to determining the end of combustion, the effect of signal noise on the pressure data, the effect of assumptions regarding the value and variation of apparent compression and expansion polytropic indices and, particularly, how these should be determined. The treatment of late burning cycles is also discussed. Versatile software has been developed for idle to full load studies with good tolerance to signal noise.