Nitrogen Oxides (NO_x) Emissions

The ECM controls the EGR or exhaust gas recirculation valve according to operating conditions. The valve prevents high combustion chamber temperatures from forming NO_x oxides of nitrogen, a smog-forming emission. This harmful gas forms if the EGR valve is not opening correctly.

The valve provides a regulated flow of inert exhaust gases into the intake manifold, lowering combustion chamber temperatures. Blending exhaust gas into the chamber keeps it at an acceptable range (below 2500° F), preventing nitrogen and oxygen from bonding. Excessive NO_x results in pollution and smog.

(VVT) Variable Valve Timing

Most modern engines have variable valve timing. VVT systems time the exhaust and intake valves, improving low-end and high-end performance. For example, holding the exhaust valve open a little longer allows some exhaust into the combustion chamber during the intake stroke, preventing excessive NO_x formation.

Three-way Catalytic Converter

A catalytic converter substrate consists of an aluminum oxide honeycomb coated with materials like platinum and palladium. They react and remove (CO) carbon monoxide and (HC) hydrocarbon from the exhaust stream.

A two-way catalytic converter works by oxidizing CO and HC to (CO₂) carbon dioxide and water. A three-way catalytic converter also removes (NO_x) oxides of nitrogen from the exhaust.