TDI engine preheating system (Audi 80 B4)

Due to the design features of direct injection engines, preheating has its own differences. These engines start without preheating at temperatures below 0°C. And if preheating is performed at these temperatures, it is primarily due to the need to regulate the content of harmful substances in the exhaust gases.

The TDI engine warm-up process consists of two phases:

• a) Warm-up. Its duration at -30°C is about 28 sec. If the engine temperature is above 0°C, then warm-up is not performed at all,
• b) Maintenance. Its duration at -30°C is about 120 sec, and at 0°C - about 30 sec. If the engine temperature is above 0°C, then maintenance is not performed at all.

The preheating system of TDI engines, unlike engines with fuel injection into the swirl chamber, consists of two parts: a control unit and a switching relay. The control unit of the injection system performs an additional function of providing preheating of the engine depending on the temperature of the coolant, and the switching relay ensures the supply and disconnection of power. The relay is located on the central distribution block under No.12.

The glow plugs used in the TDI preheating system have two heating coils and are not self-regulating. Self-regulation of the glow plugs is not necessary in this case, because they are cooled by the air admitted to the combustion chamber and cannot heat up above 1050°C.