Press Release
Cylinder heads: high cylinder charging even in partial load range The aluminium cylinder heads are designed to meet the particular demands of common rail technology. The injectors are centrally located between the four valves, thus ensuring optimum fuel distribution. The valves are controlled by two hollow-cast camshafts per cylinder bank, together with bucket tappets. Spiral intake ports in the cylinder heads, one of which in each case is optimised for swirl, the other for flow, and which are precisely matched to the symmetrically formed combustion chambers, set the air into fast-swirling motion and so ensure the ideal mixture of fuel and intake air in the partial-load range. An electro-pneumatic intake port cut-out also comes into effect in the partial-load range. By temporarily cutting off one intake port, this increases further the swirl speed of the fuel-air mixture ??????????????????????????????????????? and thus the cylinder charging rate. Exhaust gas recirculation: demand-responsive control depending on engine load and speed The intake system of the new V8 diesel engine also includes an air filter with two hot-film air mass sensors installed in the engine, which give a precise analysis of the air drawn in. These give the microcomputer responsible for the engine management the precise data that enable it, for example, to control the exhaust gas recirculation according to the engine load and speed ??????????????????????????????????????? all in the interests of lower exhaust emissions. There are two recirculation valves for the exhaust gases ??????????????????????????????????????? one per cylinder bank. These are controlled electrically by a rotary magnet and regulate the amount of exhaust gas which is recirculated, depending on the load on the engine, in a defined ratio to the intake air. Exhaust gases also flow through a heat exchanger, where they are further cooled. The emissions limits of the new eight-cylinder diesel engine fall well within the EU 3 emissions limits, not only with the help of its efficient exhaust gas recirculation system, which contributes primarily to the reduction of nitrogen oxide emissions, but above all thanks to its sophisticated catalytic converter system. This consists of two exhaust-gas purifiers located near the engine, which begin to act as oxidation catalysts very soon after a cold start and which are responsible for reducing the level of hydrocarbons and carbon monoxide by chemical bonding with oxygen. Combination: balancing shaft with centrifugal oil separator In order to keep the dimensions as compact as possible, the Mercedes engineers designing the V8 engine decided upon a cylinder angle of 75 degrees, compensating the vibrations typical of this construction concept with a balancing shaft. This is located in the space between the two banks of cylinders and rotates at the same speed but in the opposite direction to the camshaft. At the front end of the balancing shaft is an oil separator, which ventilates the engine by centrifugal force. The solid base of the V8 engine with CDI technology is formed by an aluminium crankcase, manufactured according to a new sand-casting method. The advantage of this is its increased strength, which has given the engineers much more scope in terms of engineering design. For the first time, for example, they have been able to integrate the timing case as well as the oil ducts and returns directly into the crankcase itself. This aluminium construction method not only improves the smoothness of the engine, but also helps reduce its weight: the crankcase of the V8 engine, at 56.2 kilograms, is approximately 17 per cent lighter than the comparable component in the CDI six-cylinder unit of the E 320 CDI. The eight-cylinder engine, with all its ancillary components, weighs a total of 245 kilos and is thus the lightest diesel unit in this displacement category.
