Exhaust System - Alfa Romeo 159 Training Material

ENGINE

Exhaust system

FEATURES: The engine has a 4-in-2-in-1 exhaust system with two three-way CCC ('Close Coupled Converter')
catalysers built into one. The catalysing elements are relatively close to the engine. This means that Euro 4
specifications on the emission of pollutants can be reached without adopting particular systems, such as secondary
air or electrical heating.
Double injection (lasting for approximately 50 seconds) is exploited to significantly reduce emissions thanks to the
possibility of injecting petrol directly into the chamber. Double injection is exploited to make the charge richer near the
spark plug so that the better fuel ignition quality will provide a longer ignition delay. This have two advantages: firstly
gases are hotter and therefore the catalyser warms up faster; secondly, due to the gases being hotter during
expansion and exhaust, a significant fraction of the unburnt hydrocarbons is converted before reaching the catalyser.
The content of these components is approximately 5 times lower than that of a traditional engine.
To decrease heating time and improve catalyser performance, the exhaust plenum is not exposed to the current of air
hitting the vehicle, being positioned so that the engine shields it from the wind instead.
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1. Pre-cat lambda sensor
2. Post-cat lambda sensor
3. Pre-cat lambda sensor
4. Post-cat lambda sensor
5. Heat shield
6. Nut
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ALFA 159 TRAINING MATERIAL
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