GF49.10-P-2010MOR Upstream of Three-Way Catalytic Converter

GF49.10-P-2010MOR Upstream Of Three-way Catalytic Converter
ENGINE 275.9 in MODEL 230.4 as of model year 2009 / AEJ 08 model refinement package





Front view of exhaust system

158 Firewall catalytic converter

G3/3 Left O2 sensor upstream of catalytic converter
G3/4 Right O2 sensor upstream of catalytic converter
G3/5 Left O2 sensor downstream of catalytic converter
G3/6 Right O2 sensor downstream of catalytic converter

Location
Two types of catalytic converter inserts are used respectively in near-engine mounted firewall catalytic converters.

Task
Reducing the exhaust gas emissions:

- Nitrogen oxides (NOX)
- Hydrocarbon (HC)
- Carbon monoxide (CO)





Design
Schematic diagram

1 Ceramic monolith
2 Wire mesh (embedded)
3 Double-walled housing (insulation)
4 Substrate (washcoat) with a coating of rare metal

Ceramic monoliths are ceramic bodies through which pass several thousand small passages. The exhaust gas flows through these passages. The ceramic consists of high temperature-resistant magnesium aluminum silicate.
The monolith, which is extremely sensitive to voltages, is embedded in an elastic wire mesh made of high-alloy steel wires and fitted in a double-walled stainless steel housing.
Ceramic monoliths require a substrate (washcoat) of aluminum oxide (Al2O3) that expands the active surface of the catalytic converter by an approximate factor of 7000.

The active catalytic layer coated on the substrate consists for three-way catalytic converters of platinum, rhodium and palladium.
Platinum and palladium accelerate oxidation of hydrocarbons (HC) and carbon monoxide (CO). Rhodium assists reduction of nitrogen oxides (NOX).





Function
Schematic diagram

A Exhaust not cleaned
B Exhaust cleaned
F Rich mixture
M Lean mixture
Lambda (air/fuel ratio)

CO Carbon monoxide
CO2 Carbon dioxide
HC Hydrocarbon
H2O Water
N2 Nitrogen
NOX Nitrogen oxides

The exhaust gases flow through the catalytic converter and, in so doing, come into contact with the rare metals platinum, rhodium and palladium.
^ Through oxidation, carbon monoxide (CO) is converted into carbon dioxide (CO2) and hydrocarbons (HC) into water (H2O) + carbon dioxide (CO2).
^ Through reduction, nitrogen oxides (NOx) are converted into nitrogen (N2) + carbon dioxide (CO2).

Crucial for pollutant conversion of pollutants is the residual oxygen content in the exhaust. The best pollutant conversion is obtained at lambda equals 1.

Operating conditions
For a catalytic converter the operating temperature is decisive.
Significant pollutant conversion only begins from an operating temperature of about 250°C.
The ideal operating conditions for high conversion rates and long life are found at temperatures between around 400 to 800°C.
A temperature >850°C, as can occur when there are combustion misfires, leads to thermal destruction of the catalytic converter (melting of the monoliths).

Owing to its ability to reduce three polluting components simultaneously, it is called a "three-way catalytic converter".