The combustion development of the Mercedes-Benz CNG-engine M447hLAG is discussed. This engine represents the evolution of the naturally aspirated CNG- engine M447hG [1], which will be used to exemplify the improvements achieved. The main application of the M447hLAG is the new Mercedes-Benz urban bus O530 Citaro, which is produced by EvoBus in Germany. Two power ratings are currently available:
240 kW @2000 min-1, with maximum torque 1250 Nm @1500 min-1
185 kW @2000 min-1, with maximum torque 1050 Nm @1300 min-1
The engine displacement is 11.967 liters, with 6 horizontal in-line cylinders. The combustion concept is lean-burn with closed-loop mixture control, turbocharger and charge cooler, similar to the Mercedes-Benz CNG- Engine M366LAG [2], providing low emission levels and low fuel consumption.
The new engine management system further provides fuel injection, mapped ignition timing, full airflow control and total compatibility with the Mercedes-Benz Star-Diagnose and 24V CAN system used in the new Mercedes-Benz heavy-duty commercial vehicles.