Question

there is one condition when oxides of nitrogen are being created in large amounts and the egr valve does not operate; it is

a. when the vehicle is at top speed
b. when the vehicle is operated at wot
c. when the vehicle is warm at idle
d. when the vehicle has just been started

Explanation:

Oxides of nitrogen (\(NO_x\)) are formed at high combustion temperatures. The Exhaust Gas Recirculation (EGR) valve is designed to reduce \(NO_x\) emissions by recirculating a portion of the exhaust gas back into the combustion chamber. When the engine is operated at Wide - Open Throttle (WOT), the engine is under high load. At high loads, the combustion temperatures are very high, leading to significant \(NO_x\) formation. Also, under WOT conditions, the EGR valve does not operate because recirculating exhaust gas at this time could potentially reduce engine power output.

• Option a: Just being at top speed does not necessarily mean high combustion temperatures if the engine is not under high load (e.g., coasting at top speed).
• Option c: At idle, the combustion temperatures are relatively low, so \(NO_x\) formation is not significant, and the EGR valve may operate (depending on engine design) to further reduce emissions.
• Option d: When the vehicle has just been started, the engine is cold. Cold - start conditions are more about incomplete combustion (higher \(HC\) and \(CO\) emissions) rather than high \(NO_x\) formation (since combustion temperatures are not extremely high yet), and the EGR valve may not be fully functional due to engine warm - up requirements.

Answer:

B. When the vehicle is operated at WOT