Catalytic-converter mounted close to the engine

Two monoliths are located within the catalytic converter's housing. The catalytic converter's total volume is 2.7 litres. The monoliths have various coatings.

Monolith 1 on the N55 engine has the following characteristics:

• Volume = 1.2 litres
• Diameter = 125 mm
• 600 cells.

Monolith 2 on the N55 engine has the following characteristics:

• Volume = 1.5 litres
• Diameter = 125 mm
• 400 cells.

The catalytic converter reduces emissions of the following pollutants:

• With the aid of oxygen (O₂ ) carbon monoxide (CO) is converted into carbon dioxide (CO₂ ).
• Hydrocarbons (HC) react with oxygen (O₂ ) to form carbon dioxide (CO₂ ) and water (H₂ O).
• Nitrous oxides (NO_x ) break down into nitrogen (N) and oxygen (O₂ ).

The following illustration shows the catalytic converter on the F10.

Fig 1: Identifying Catalytic Converter, Oxygen Sensor

Courtesy of BMW OF NORTH AMERICA, INC.

At all times, the Digital Engine Electronics (DME) regulate the fuel-air mixture with regard to the following criteria:

• Exhaust emissions
• Consumption
• Power development
• Catalyst protection.

The DME digital engine electronics system relies on the oxygen sensors to monitor levels of residual oxygen in the exhaust gas and then dials in corrections in fuel-injection quantities using these data. A model for exhaust-gas temperature integrated in the DME digital engine electronics system discharges the following functions (among others):

• The catalytic converter heater ensures rapid heating and catalytic conversion soon after the engine starts.
• The effect of the catalytic converter protection is that the exhaust-gas temperatures, in particular at full load, are regulated in such a way that a thermal overload of the catalytic converter is prevented.