The OM654 engine is Mercedes-Benz’s first all-aluminum diesel four-cylinder motor. The OM654 is part of a new modular engine family, and can be linked to form whatever configuration the company wants – and it’s all part of Daimler’s new approach to engine development in the wake of the VW emissions scandal.
Compared to its 2.1-litre predecessor, the OM654 consumes 13 percent less fuel and emits 13% less CO2 per mile, according to Mercedes. The OM654 also produces 191 horsepower and 295 pound-feet of torque, making it a powerful new addition to the Mercedes line up.
It’s a logical move on the part of Mercedes to introduce a lower-powered engine in their range, as it can be used in more vehicles than their bigger engines can, and will reduce the amount of maintenance required. As a result, it should be more affordable to purchase than the older models.
If you’re looking to buy a Mercedes with this engine, it’s important to understand that it is not for short trips and city commuting, as it will cause carbon build-up, oil dilution and blocked DPF filters, all of which will shorten the engine’s life span and potentially cost you money in the long run.
In addition to this, you should keep in mind that these engines will need to be inspected after every few thousand miles or so, and it’s always best to have an independent mechanic inspect them. They will be able to tell you if there are any signs of oil leaks and if the water pump, thermostat or radiators need repairing.
The engine also has a multi-way exhaust gas recirculation system, and Mercedes says that the interaction of low-pressure EGR actuators with high-pressure EGR valves reduces fuel consumption and CO2 emissions. The OM654 also features a new, compact piston that is said to cut friction in the combustion process and improve airflow.
As a result, the OM654 has a better combustion process and a lower fuel consumption than its OM651 predecessor. It also has a more efficient turbocharger.
A new piston design is the key to this efficiency boost, with the new, flat piston delivering a lower friction ratio than its omega-shaped predecessor, with a smaller step-recess profile enabling the cylinder to expand more slowly, helping reduce friction in the combustion chamber. This, combined with a Nanoslide arc-sprayed cylinder liner and longer connecting rods, will help to reduce particulate emissions in the air stream.
Lastly, the OM654 has a cooled high-pressure and low-pressure exhaust gas recirculation system that helps to increase combustion temperatures and assist in the regeneration of the diesel particulate filter (DPF). The engine also has an oxidation catalytic converter that converts pollutants into harmless compounds.
The OM654 has a fourth-generation common-rail injection system that combines the Bosch CP4 single-piston fuel pump and eight-hole piezo fuel injectors. This combination is said to allow for a higher air-fuel ratio than the previous OM651, which allowed for more precise control of air intake and exhaust pulses, resulting in better power output.