General description
Unlike the diesel engine with swirl chamber fuel injection, TD1 engines have electronically controlled direct injection. It is based on the control unit and the BOSCH VP 34 high pressure fuel pump.
The task of the control unit is to process information from numerous sensors and perform the following actions:
- control of the start of injection and the amount of injected fuel. This regulation is carried out with the help of two autonomous actuators;
- glow plug control;
- turbocharger boost pressure regulation;
- EGR control.
Double-spring nozzles are used to reduce engine noise (see illustration 1.0b), providing a softer mode of combustion of the mixture. For the same purpose, the injection pump is closed with a protective cover. Double-spring injectors are not compatible with the control unit and injection pump installed on cars of earlier releases. Therefore, the installation of the mentioned injectors on cars manufactured before 6/92 is not possible.
Since 7/93, the power supply system of vehicles with a TDI engine has undergone some changes. Instead of an intake air volume flow meter, an air mass flow meter is installed, on which a heating film is used instead of a glow wire. Changes have also been made to the design of the injection pump. The pump in the current version does not have a control spool potentiometer. Information about the position of the spool enters the control unit from the solenoid valve. The control unit itself has also changed. Now the intake manifold pressure sensor, located on the right rear of the engine on earlier models, is located in the control unit and is connected by a low pressure hose to the intake tract. Altitude corrector, previously located in the control unit, «migrated» into the passenger compartment and installed behind the passenger footwell trim. In addition, the small turbocharger, designed to increase torque in the lower engine speed range, as well as the boost pressure control solenoid valve have also been moved and are now located in the front right side of the engine compartment (earlier - back right side). The fuel filter condensation level sensor is no longer installed.
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