HARRIER SERVICE MANUAL PART -1

ELECTRICAL 52 11 GLOWPLUG CONTROL UNIT LOCATION The Glow Plug Interface Unit mounted on water channel RHD OPERATIONAL DESCRIPTION The aim of Glow Plug Interface Unit (GPIU) is to achieve high degree of flexibility in driving the glow plugs that are included in a standard EMS system for diesel engines. It is evident that the requirement for GPIU depends from the driving characteristics required by the glow plugs. In a modern direct injection diesel engine the function developed by glow plug may be summarized as follows: Auxiliary starting device Cold diesel engines due to high levels of internal frictions & thermal losses are reluctant to start. Often need of auxiliary devices like glow plugs are the only method to guarantee engine start. The glow plug power dissipation increases the combustion chamber temperature allowing the air fuel mixture to reach its self-ignition condition. Auxiliary combustion control device The air fuel mixture self-ignition points are mainly influenced by two factors: pressure & temperature inside the combustion chamber. The temperature control in all those condition in which the combustion chamber is relatively “cold” (i.e. during cut-off or during post-start) may improve the reduction of ignition delay with large benefit in terms of emission & combustion efficiency. Auxiliary Power Management device The total power dissipation of glow plug is not negligible (it may vary from 240W to 750W according with glow plug characteristics). In some cases, it may be useful to increase the engine load operating point in order to achieve higher exhaust temperature (e.g. in order to start the regeneration of diesel particulate filter). The glow plug activation in this condition may help either directly, increasing combustion temperature indirectly increasing engine load as required. The features of modern Glow plug Interface unit must allow the EMS to operate in all of above conditions with possibility to choose the driving method & parameter optimization. Command & feedback Signal Description Command signal The glow plugs are supplied by control unit with battery voltage (12V). The glow plug temperature is controlled by ECU through a function stored in memory, which links glow plug temperature with the duration of heat signal (12V). Feedback Signal Feedback signal given by glow plug controller to EMS ECU. Glow plug informs the EMS ECU whether the command given by ECU is followed. Circuit Diagram