The implementation of the national six emission standard is imminent. In the first half of the year, all main engine manufacturers are vigorously digesting the national five inventory and verifying the new products of national six. As we all know, in addition to the conventional performance test and reliability test, national six models also need a large number of environmental adaptability verification based on the actual operating conditions of users. Foreign heavy trucks are verified by manufacturers in this link, Due to China’s vast territory and complex working conditions, in order to reduce the verification cycle and reduce the development risk, domestic main engine manufacturers will conduct test verification in the customer trial mode in the early stage. Next, let’s talk about a case of “torque limiting”.
Torque limit is a common problem of national six vehicle models. It is a control logic forcibly added by the manufacturer to force users to use the vehicle normally and meet the exhaust emission requirements. It is also called primary driving performance limit. When the emission exceeds the OBD limit and the problem is not solved for more than 10-36 hours, the vehicle realizes torque limit and limits the vehicle power output, and the vehicle torque will be reduced by 25%.
In fact, the national five models also require torque limiting treatment for substandard exhaust, but the relative requirements are relatively loose, so such faults rarely occur, but the national six models have higher requirements, which is like a child’s “fever”. When inflammation occurs in a child’s body, it is a “fever”, which has reminded “eliminate inflammation”.
In fact, the reasons for the “limited torsion” of the national six heavy truck are as follows:
1. The residual amount of reagent (urea) is lower than the rated capacity range, and the urea quality does not meet the standard.
2. The EGR valve is stuck for a certain period of time.
6. Tamper proof detection system (post-processing monitoring, including various post-processing sensors, circuits, etc.) fails and lasts for a certain time.
Xiao Wu from Northeast China is a card friend with 10 years of driving experience. In July last year, he chose to buy a “national six” tractor. The price of this car was 30000 cheaper than that of national five. The manufacturer also gave a very preferential policy at that time. He gave a 85% discount for the new car, He also gave away two years of TCO (custody service), which completely dispelled Xiao Wu’s concern about the immaturity of the technology of the national six model. However, Xiao Wu still encountered a lot of troubles in the process of sports cars, and the biggest problem is the vehicle torque limit.
When it comes to “torque limitation”, Xiao Wu’s conversation box opens. He said that he signed an agreement with the manufacturer that he must add fuel from the regular service station and the original urea from the service station. Xiao Wu is really unambiguous and does it according to the manufacturer’s requirements, but there is still a “torque limitation” in this way. He was really flustered.
Once when he went to Harbin, it was cold. He called the service station to deal with it. Because the service station was not skilled in the maintenance of national six vehicles, he saw that the national six vehicles were hairy. He checked all the engines and exhaust for a day and found no problems. Finally, the manufacturer arranged technicians to replace the EGR valve.
EGR valve is a product installed on the diesel engine to control the amount of exhaust gas recirculation fed back to the intake system. It is usually located on the right side of the intake manifold, close to the throttle, and connected with a short metal pipe leading to the exhaust manifold.
EGR valve reduces the combustion chamber temperature, improves the engine working efficiency, improves the combustion environment, reduces the engine burden, effectively reduces the emission of no compounds, reduces knock and prolongs the service life of various components by guiding the exhaust gas from engine combustion to the intake manifold for combustion.
Automobile exhaust gas is a kind of non combustible gas, which does not participate in combustion in the combustion chamber. It reduces the combustion temperature and pressure by absorbing part of the heat generated by combustion, so as to reduce the generation of nitrogen oxide.
The function of EGR valve is to control the amount of exhaust gas entering the intake manifold to make a certain amount of exhaust gas flow into the intake manifold for recirculation.
When the engine is running under load, the EGR valve is opened to re introduce part of the exhaust gas into the cylinder in a timely and appropriate manner. Because the specific heat capacity of the main component CO2 in the exhaust gas is relatively large, the exhaust gas can absorb part of the heat generated by combustion and take it out of the cylinder, and has a certain dilution effect on the mixture. Therefore, the maximum combustion temperature and oxygen content of the engine are reduced, Thus, the generation of NOx compounds is reduced.
The position sensor (or exhaust gas temperature sensor or pressure sensor) is set at the EGR valve of guoliu engine to carry out closed-loop correction feedback control for the actual exhaust gas recirculation amount. The amount of exhaust gas participating in recirculation can be automatically adjusted according to the changes of the actual working conditions and working conditions of the engine.
If the EGR valve is stuck, the actual amount of exhaust gas entering the intake manifold will be uncontrollable.
Excessive exhaust gas recirculation will affect the normal operation of the engine, have a serious impact on the performance of the engine, affect the power output of the engine, and lead to insufficient engine power.
Too little exhaust gas in circulation will affect the temperature of engine combustion chamber and increase the emission of no compounds, resulting in substandard emission and engine torque limit.
National six models not only bring more stringent emission requirements, but also bring more technical problems. In the process of product promotion, car enterprises also need to do a good job in product technical verification and after-sales service training, otherwise they will be abandoned by card friends in the process of national six technology upgrading.