Fuel Delivery and Air Induction: Description and Operation
MOTRONIC FUEL SYSTEMFUEL TANK AND PUMP
The Motronic fuel system for the 20v turbocharged 5 cylinder is equipped with a 21 gallon fuel tank mounted under the rear of the vehicle. An electric fuel pump that is mounted inside the tank pumps fuel through an externally mounted fuel filter to the rest of the fuel system.
FUEL RAILS AND PRESSURE REGULATOR
The in-tank mounted fuel pump delivers fuel to the fuel rail. Fuel is distributed to the injectors via the fuel rail. A fuel rail mounted pressure regulator maintains fuel pressure at the injectors so there is approximately a 58 psi (4.0 bar) pressure difference to the intake manifold pressure. The intake manifold pressure influences the fuel pressure via the pressure regulator. This ensures that the difference in pressure between the intake manifold pressure and the fuel pressure remains constant.
FUEL INJECTORS
The fuel rail mounted injectors are solenoid-type four hole two spray versions. This configuration prevents puddling in the land area between the intake valves.
Each injector has its own connection pin at the Motronic engine control module. This allows the ECM to recognize a fault in a single injector. A separate output stage (switching unit) located inside the Motronic ECM is provided for each injector. The output stages are used to complete a ground circuit for the injectors. Multiple output stages are necessary for sequential injection and fault diagnosis.
TURBOCHARGING SYSTEM
This engine is equipped with a turbocharger and electronic charge pressure control. Charge pressure control makes it possible to keep the charge pressure at a programmed value throughout the entire engine speed range.
The charge pressure is regulated by a charge pressure map stored in the Motronic ECM memory. The charge pressure is based on throttle valve opening angle and speed in which the throttle is being opened.
Maximum charge pressure is 2.15 bar (31.17 psi) although the charge pressure control system allows the system to generate an "overboost" condition for a short period of time. Overboost is controlled via the charge pressure map inside the Motronic ECM. The ECM identifies full acceleration situations and allows for the overboost condition. The overboost condition has a time limit of 15 seconds. The 15 second time limit helps ensure favorable drivetrain durability over the life of the vehicle.