Abstracf-The Homogeneous Charge Compression Ignition (HCCI) combustion concept lacks direct ignition timing control, instead the auto ignition depends on the operating condition. Since auto ignition of a homogeneous mixture is very sensitive to operating conditions, a fast combustion timing control is necessary for reliable operation. Hence, feedback is needed and the crank angle of SO% burnt (CASO) has proved to be a reliable feedback indicator of on-going combustion in practice. CAS0 or other methods for detecting on-going cylinder pressure used in the feedback control of a HCCI engine all rely on pressure sensors. This paper presents a new candidate for control of HCCI engine by using the electronic conductive properties in the reaction zone. This phenomenon is called ion current. This paper perform combustion timing control based on ion current and compare it with control based on pressure sensor. The combustion timing control is performed on cycle-to-cycle basis and the engine is a onecylinder version of a heavy duty engine equipped with a pori injection system using dual fuels.