  Reduction of heat and friction losses is a proven approach to increase the
engine efficiency. Therefore, and due to a stabilized, robust combustion, a
specific adjustment of component temperatures is desirable in highly transient
conditions. In this paper, a turbocharged SI engine is investigated numerically
concerning the potential regulation of temperatures, including heat fluxes,
only by controlling the water mass flow rate. Using two independent models, a
simplified lumped capacity model and a detailed three-dimensional CFD-CHT
simulation, an efficient, two-stage calculation method is suggested for an
optimized determination of control strategies and their parameters. This
complements existing published works which usually control more than one
parameter, but use one model. Different control strategies, like feed forward
or feedback controllers, are proposed and compared. In addition, a more
holistic approach is presented performing a Monte Carlo simulation which
evaluates temperatures, as well as hydraulic pumping losses. Using expedient
control strategies and parameters, it could be shown that the engine
temperatures can be effectively regulated within a wide range. The two
different models show partly similar results, and the efficient, two-stage
optimization method has proven its worth. However, there are some significant
differences between simplified and detailed modelling which are worth
mentioning.
