What is the reason for adding urea to a vehicle?

[OAndrew]

Here are the reasons for adding urea to a vehicle: 1. Primarily to meet emission standards. Only diesel vehicles require urea addition. National regulations mandate that electronically controlled diesel engine vehicles must add urea because diesel vehicles emit higher levels of exhaust. Adding urea helps reduce carbon oxides in the exhaust, lowering pollutant emissions and making diesel vehicles more environmentally friendly. 2. Currently, most diesel engines use Selective Catalytic Reduction (SCR) technology. This means that after the engine exhaust exits the turbocharger and before entering the vehicle's exhaust pipe, it needs to pass through a catalytic converter for transformation. The urea nozzle on the exhaust pipe sprays urea under the control of the vehicle's computer. The urea reacts with nitrogen oxides in the exhaust gas within the catalytic converter, undergoing a redox reaction that ultimately converts the vehicle's exhaust into nitrogen and water before being emitted.