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Homogeneous Charge Compression Ignition, HCCI, has the attractive feature of low particulate emission and low Nitrogen Oxides, NOx, emission combined with high efficiency. The principle is a combination of an Otto and a Diesel engine in that a premixed charge is ignited by the compression heat. One of the main challenges with the HCCI combustion system is to control the Start Of Combustion, SOC, for varying load and external conditions. A method to achieve this on a cycle-by-cycle basis is to vary the valve timing based on a feedback signal from the SOC of previous cycles. The control can be achieved with two basic valve-timing strategies, named the Overlap- and the IVC-method. The Overlap-method works by trapping of residuals while the IVC-method affects the effective compression ratio. These methods have in an earlier paper been verified to work one at a time to control SOC during engine transients [1].