Direct ignition system (Peugeot 405)

Ignition system in the engine with a working volume of 1998 cm³ model XU10J4 (with 16 valves) has a "direct" type. The system components consist of two amplifier modules, four ignition coils and a knock sensor. The ignition system is integrated with the fuel injection system into the engine management system ECU (through ignition amplifier blocks).

Each ignition amplifier unit controls two ignition coils: one integrated with the spark plug caps and one mounted directly on the spark plugs, one coil per spark plug. This eliminates the use of high-voltage wires. The ECU uses inputs from various sensors to calculate the required ignition timing and the energy accumulation time of the ignition coil.

The knock sensor is mounted on the cylinder head and prevents detonation in the cylinders under load. The sensor is sensitive to vibration and detects detonation, which occurs when the fuel mixture in the cylinders burns with detonation. The knock sensor sends an electrical signal to the ECU, which in turn reduces the ignition timing until detonation stops.