Mercedes-Benz OM611 engine
In-line five -cylinder OM 612 In-line six -cylinder OM 613
The OM 611 Mercedes- Benz is a four-cylinder diesel engine with common - rail direct injection. In 1997 he was presented in the model C 220 CDI. The article also discusses the engines OM 612 and OM 613 with five or six cylinders, also series engines which are technically related closely with the OM 611.
Technology
Generally
In the Mercedes -Benz OM 611 is a four-cylinder diesel engine with two overhead camshafts which operate the 16 valves via bucket tappets. For the first time, the OM 611 was sold in September 1997 in the C-Class under the name C 220 CDI. The OM 611 has compared to the previous model OM 604 30 % more power, 50 % more torque and 10% less consumption. For purifying exhaust gas, an oxidation catalyst is used. Since the efficiency is increased with the new generation of engines at low outside temperatures are not sufficient heat for a sufficient inner space heating is provided. This problem was encountered in the CDI - II Series by an electric heater was installed and in the CDI series I with a diesel-powered heater. The camshaft is driven by a duplex roller chain.
Injection
Feature is the first use of a common-rail direct injection Bosch in a Mercedes -Benz engine model. The fuel is distributed via a common fuel line (common rail), in which the fuel pressure is kept up continuously by a high pressure pump. Through the conduit of the fuel reaches the solenoid valve-controlled injector, from where it is injected at a pressure of up to 1350 bar by means of holes 6 in the combustion chamber. By the pilot injection in which a small amount of fuel is introduced and burned prior to the actual combustion in the cylinder, the combustion chamber preheats, so the temperature and pressure rise is not as strong in the main combustion fails. This makes for a much smoother operation. In the CDI series II, the injection system to a high pressure control with pressure control valve, flow control valve, a mechanical fuel pump and a fuel temperature sensor has been added.
Charging
The motor is ventilated via a turbocharger with a bypass valve (so-called wastegate ). Since the turbocharger is driven more and more with increasing engine speed due to the higher amount of exhaust gas, the compressor delivers even more air. This in turn leads back to an even greater waste gas stream, which in turn drives the turbine even further. To avoid damage by mechanical or thermal stress, the charge must be limited ( boost control ). For this purpose, a bypass valve is used in series I CDI, which is opened at a certain pressure and over charge diverts the exhaust gases from the loader into the exhaust system. A further rise in the turbine speed is thus prevented. CDI in series II was replaced by a turbocharger VNT loader. VNT stands for Variable Nozzle Turbocharger ( ger variable turbine geometry loader ) and means that variable guide vanes are mounted on the exhaust side. The control is effected by means of vacuum. This technique results in the low speed range to a faster build up boost. This becomes evident in the improved cylinder charging and therefore higher torque. To cool the hot charge air to an optimum temperature, a charge air cooler has been fitted.
Intake tract
In the intake tract of the OM 611, the CFST (intake port shut-off ) is used. Of the two intake ports for each cylinder, a channel ( tangential ) may be turned off at low speeds. The sucked air then flows entirely through the specially shaped second passage ( swirl passage ). The resulting swirl leads to an improved mixture formation, resulting in better combustion. In the CDI series I, the CFST is pneumatically driven while the CDI series II received an electronically controlled and continuously working FCOS. Another new feature of the CDI Series II is the pneumatically controlled exhaust gas recirculation valve dar. It reduces the excess air and lowers the temperature peaks by exhaust gases from the fresh intake air to be supplied. Characterized the emission of nitrogen oxides and combustion noise are reduced. To control the exhaust gas recirculation, a hot-film air mass meter is installed which allows a detailed analysis of the aspirated air mass.
Five-cylinder OM 612 and OM 613 six-cylinder
Parallel to OM 611 OM 612 series were (5- cylinder) and OM developed 613 (6- cylinder), the 611 form an engine family with the 4 -cylinder OM brother. Thus, these engines have the same displacement per cylinder and there are inline engines. All engines from the OM 612 and OM 613 model series based on the CDI Series II
A special feature of the OM 612 DE 30 LA dar. This engine is based on the OM 612 DE 27 LA, however, was of AMG, the stroke is increased by a larger capacity to achieve. Due to the increased engine output torque and the increased number of components had to be re- constructed and adapted to the increased load. So the crank mechanism has been strengthened, the Zylinderkopfverschraubung optimized, used an oil pump with a larger promotion-related assets and built reinforced pistons with oil injection cooling the piston crowns. The glow system was redesigned and, with the higher annealing temperature warms up faster a safe. The idle behavior could be optimized by an improved control of Nachglühverhaltens.
To ensure maximum performance and torque yield even at high outside temperatures, came for the charge air cooling a unusual design used: The intercooler is located right next to the engine and equipped with an air -water heat exchanger. The heat is dissipated via a separate low-temperature water circuit to two separate from the actual engine cooling radiator in the front.
Unlike the regular 612 OM - motors the displacement of the guide vanes of the VNT turbocharger with engine electronics are; the adjusting operation is therefore faster than in the case of pneumatic control. The exhaust gas recirculation valve has been modified and also received an electronic control. Together with the close-coupled, the thin-walled front wall of the catalyst, it provides an improved emission control. The exhaust system has a pipe diameter of 76 mm and thus contributes to improved performance.