General description
Unlike a diesel engine with swirl chamber fuel injection, TD1 engines have direct injection regulated by an electronic control unit. It is based on a control unit and a BOSCH VP 34 high-pressure fuel pump.
The control unit is tasked with processing information from multiple sensors and performing the following actions:
- regulation of the start of injection and the amount of fuel injected. This regulation is performed using two independent actuators;
- glow plug glow control;
- turbocharger boost pressure control;
- eGR control.
To reduce engine noise, dual spring injectors are used (see illustration 1.0b), providing a softer combustion mode of the mixture. For the same purpose, the high-pressure fuel pump is covered with a protective cover. Two-spring injectors are incompatible with the control unit and high-pressure fuel pump installed on cars of earlier production. Therefore, installation of the mentioned injectors on cars manufactured before 6/92 is impossible.
Since 7/93, the fuel system of cars with a TDI engine has undergone some changes. Instead of an air flow meter, an air mass meter is installed, which uses a heating film instead of a glow wire. The design of the high-pressure fuel pump has also been changed. The pump in the current version does not have a potentiometer for the regulating valve. Information about the position of the valve comes to the control unit from the electromagnetic valve. The control unit itself has also changed. Now the pressure sensor in the intake manifold, located on the right in the rear part of the engine in earlier models, is located in the control unit and is connected to the intake tract by a low-pressure hose. The altitude corrector, previously located in the control unit, "migrated" to the passenger compartment and is installed behind the trim of the footwell of the passenger seat. In addition, the small turbocharger, designed to increase torque in the lower engine speed range, as well as the electromagnetic valve for regulating the boost pressure have also been moved and are now located in the front right part of the engine compartment (previously - the rear right part). The condensate level sensor in the fuel filter is no longer installed.
