Reasons for High NOx Emissions in Vehicles
2 Answers
Vehicle NOx emissions are too high for the following reasons: 1. The DEGR system is not working properly and needs to be repaired as needed. 2. The input sensor of the ignition control system is faulty, resulting in an excessively lean air-fuel mixture. 3. The engine operating temperature is too high. 4. The intake air temperature is too high, and the intake air temperature regulation system and turbocharged intercooler system should be checked. The following are the reasons that affect excessive NOx emissions: 1. The vehicle's fuel line is blocked, the fuel injector is clogged, or the fuel injection volume is insufficient, causing the oxygen content in the engine to be too high. The CH and CO immediately discharged from the engine are too low to reduce NOx, affecting the vehicle's excessive exhaust emissions. 2. The three-way catalytic converter is faulty. After the three-way catalytic converter fails, it cannot catalyze the chemical reactions of CH, CO, and NOx, resulting in excessive vehicle exhaust emissions.
I have personal experience with high NOx issues in cars, having driven for over a decade, and it's commonly seen in older vehicles. The first reason is the engine's combustion temperature being too high, such as when the engine is running at high RPMs during highway driving, causing nitrogen to directly oxidize into NOx under high temperatures. The second reason is an imbalance in the air-fuel ratio—if the mixture is too lean with excess air and oxygen, or if the ignition timing is off, it exacerbates the problem. The third issue is a malfunctioning EGR system, which is designed to recirculate exhaust gases to cool the combustion zone. If it gets clogged or corroded, it fails, leading to a spike in NOx emissions. Poor maintenance, such as an aging or heavily carbon-fouled catalytic converter, weakens its purification ability, causing exhaust emissions to exceed standards. I've observed worsening urban pollution due to NOx, which is highly harmful, contributing to acid rain and respiratory diseases. Therefore, I recommend regular annual inspections, using low-sulfur fuel, and replacing the catalytic converter—it's cost-effective and highly effective.
