Type system "Common Rail" makes it possible to combine the diesel fuel injection system with various remotely performed functions, and at the same time allows increasing the accuracy of control of the fuel combustion process. Cleaned outside air, after a turbocharger with variable geometry and intermediate cooling of the air-to-air type, enters the cylinders under pressure. As a result, its temperature decreases, and the degree of filling in the cylinder increases.
The distinctive feature of the system with a pressure accumulator is the separation of the pressure-generating unit and the injection unit, which makes it possible to increase the fuel injection pressure and the degree of its atomization. The basis of the system type "Common Rail" consists of a high-pressure fuel pump (HPFP), a hydraulic accumulator (ramp) of fuel with its connections to the injectors (electromagnetic injectors) and an electronic control system of the "DDE" type. Injectors provide the supply of the required amount of fuel into the combustion chamber at a precisely set point in time, which is calculated by the electronic control unit (ECU). The amount of injected fuel is determined by the time interval of the open state of the injector, with constant pressure in the system.
The engine of this series is six-cylinder, in-line, installed vertically in the car. It uses a 24-valve gas distribution mechanism (GRM), with an overhead camshaft arrangement (dOHC system) and lever drive of vertically arranged valves. The gap in the valve drive is compensated by the lever resting on the hydraulic compensator. The shafts are driven by a roller chain through the crankshaft sprocket.
With strong engine overcooling and low ambient temperatures, air compression cannot always provide the temperature for fuel self-ignition. When starting a cold engine, the combustion chamber volume is heated by a glow plug for 30 seconds. In parallel with the combustion chamber heating, the automation ensures earlier fuel injection at the moment of starting. With the setting of the engine operating temperature (85 – 95°C), the automation sets the optimal angle of the start of the feed (injections) fuel. Regulation of the start of fuel injection and its quantity is provided by the program of the electronic control unit "DDE" (Digitalt Diesel-Elektronik), digital engine management system (DES) based on a personal minicomputer. The "DDE" system is also responsible for regulating the boost pressure and ensuring exhaust gas toxicity standards.
Fuel supply from the vehicle's tank is provided by a fuel pump installed in the fuel tank. Under increased loads, fuel is supplied to the HPF from the main (intermediate) fuel pump, which ensures a constant pressure in the system of 1400 kgf/cm², necessary for spraying the injected fuel. The amount of injected fuel and the order in which it enters the chambers is determined by the ECU of the "DDE" system.
The BMW X5 series car with a diesel engine of the "M57" and "M57TU" models has the index "530d". The design of the engines is identical, except for their control systems. The technical parameters of the engines are given below.
(The article text was copied from an online resource «BMWman.ru»)