Describe at least three strategies for reducing exhaust emis

Describe at least three strategies for reducing exhaust emissions during cold start-ups.

Solution

1. During cold start the exhaust temperatures are low and the catalytic converter does not light off instantaneously. In order to bring up the exhaust temperatures fast, the injection timing is delayed which leads to higher exhaust temperature, thereby lighting off the catalyst faster.

2. Another starategy for faster lightoff is secondary injection. Some fuel is injected just before the catalyst and this again helps in faster lightoff of catalytic converter.

3. Dynamically controlling the air-fuel ratio inside the cylinder during the transient conditions which occur during the start-up phase is another strategy to reducing the exhaust emissions during cold conditions.