More torque by virtue of a newly developed variable intake manifold

Mercedes engineers have considerably improved the air supply to the engine by means of a variable intake manifold with long intake ducts. This consists of three plastic shells and features an electro-pneumatically controlled actuation wheel which opens or closes the ducts according to the load and engine speed. At low engine speeds the intake air flows to the cylinders via four long intake ducts to obtain a high torque yield. This creates pressure waves in the intake ducts which support the intake process. At high engine speeds the flaps close these intake ducts, so that the air takes a direct path to the combustion chambers via a short intake duct. The engine computer decides whether and when the actuation wheel opens or closes the ducts on the basis of stored characteristic maps which ensure optimal engine operation.

The turbocharged engine newly developed for the A-Class has no variable intake manifold. Instead the intake air flows from the air filter to the turbocharger, which is located in the exhaust manifold to save space. The flow of exhaust gases required to drive the charger turbine is controlled by a pneumatically regulated wastegate valve, depending on the current engine operating point. The compressed intake air flows from the turbocharger through an intercooler, which is in turn linked to the throttle valve actuator.

The outstanding torque characteristics of the 142 kW/192 hp engine confirm the high efficiency of the turbocharger, which was developed by Mercedes engineers together with their DaimlerChrysler Research colleagues. A special turbine geometry ensures excellent responsiveness even at low engine speeds, making possible the extremely wide torque plateau available between 1800 and 4850 rpm.