Precautions for using urea in vehicles

1. Regularly check the level of urea solution in the urea tank, and add urea solution in time. The amount of urea solution used in vehicles is 3%-8% of the diesel consumption. According to the itinerary, the amount of urea solution is estimated. If necessary, bring enough barreled urea with the vehicle.

2. When filling the urea solution for vehicles, a special filling pipe should be used to prevent the mixing of sundries.

3. After filling the urea solution, tighten the lid of the urea tank to prevent the pollutants in the air from entering and causing the urea to deteriorate or crystallize.

4. The vehicle urea solution is alkaline and corrosive to a certain extent. It should be avoided that the vehicle urea solution is connected to metals (except stainless steel). These materials will react with the trace amount of ammonia in the vehicle urea solution to form compounds that affect the SCR work.

5. During transportation and storage of urea solution for vehicles, light and high temperature should be avoided, and the transportation and storage temperature should be -5℃-25℃. When the urea solution for vehicle is at a low temperature of -11°C, urea crystals will be precipitated. When adding urea solution, use <30°C warm water to dissolve the crystals, which will not affect the normal use of the urea solution for vehicles.

6. The consumption of urea solution for vehicles is related to fuel consumption and on-board SCR system, and has nothing to do with the brand of urea. The amount of urea injected from the urea filler is controlled by the engine ECM. Based on the transmitted information from the NOx sensor, the exhaust gas temperature sensor and the urea pressure sensor, the EMC controls the urea pump to use the injector to inject urea into the exhaust pipe, where it is evenly mixed with the engine exhaust gas and chemically reacts on the carrier of the silencer to clean the exhaust gas.

Sometimes the EMC is not well matched with sensors, urea pumps and nozzles, which can very easily lead to a mismatch between the amount of urea sprayed and exhaust emissions, which not only leads to a waste of urea solution but also leads to excess ammonia pollution of the air.

7. Do not turn off the vehicle main power for at least 30 seconds with the engine off, the SCR system will discharge residual vehicle urea solution in the pipe to avoid crystallization blocking the nozzles.

8. The vehicle-mounted SCR system is equipped with an auxiliary heating system, which is controlled by the urea injection control unit (DCU), which can ensure the normal operation of the SCR system in the environment of -30 °C, and there is no need to worry about the crystallization of urea solution for vehicles in winter.

9. The urea tank sensor can only sense the temperature and level of the urea solution, but cannot detect the quality of the urea solution. The urea tank sensor of some models has a certain memory function for the content of the urea solution, and the replacement of different brands of urea solution will report to the on-board computer ( ECU) to issue an alarm, if this happens, you can contact the relevant 4S shop to upgrade the system. This alarm does not judge the quality of the urea solution.

10. The urea injector installed on each vehicle is in one-to-one correspondence with the urea injection control unit (DCU), and should not be used interchangeably.

11. The filter needs to be cleaned regularly to maintain normal injection pressure. The filter maintenance and replacement cycle is 50,000 kilometers or 1,000 hours. When the urea aqueous solution is polluted, the life of the filter will be shortened.

12. The crystallization of urea solution is a common phenomenon, but it cannot be cleaned with cleaning agents. Commercially available cleaning agents will damage the key element catalysts in the SCR system. The best solution is to use hot water to flush, which will not damage the SCR system, but also effectively remove crystals.

13. The failure of the SCR system will not affect the normal operation of the engine, but if the SCR failure continues for a long time, it will cause the exhaust emission to exceed the standard. At this time, the emission indicator light (MIL) on the instrument panel will light up.

In the event of a more serious failure, the vehicle will activate the engine torque limiter to reduce engine power.

In addition, before the SCR catalytic muffler, the urea crystallizes seriously, which will block the exhaust nozzle, causing the back pressure of the exhaust nozzle to increase, resulting in increased fuel consumption.