EGR or SCR, which is more efficient?

Let's start with the meaning of high-efficiency SCR, which deals with NOx and other harmful substances that the engine doesn't clean up by injecting more urea into the aftertreatment.

As the engine omits the EGR component, the exhaust gas discharged from the engine will not be burned twice, but just burned once and then discharged directly into the aftertreatment. So more nitrogen oxides can not be processed in the engine combustion process, can only rely on the SCR system to inject more urea to break down more ammonia to neutralize the nitrogen oxides to meet the emission standards.

The advantage of high-efficiency SCR is the elimination of the EGR system, the need for the engine's single exhaust emission standards are higher, the requirements for the engine components will be more demanding, in general terms, the engine will be more high-tech.

But it also has a more prominent disadvantage, which is that it needs to spray more urea to solve the problem of exhaust gas treatment. On average, you have to spray 20% more urea per 100 kilometers than trucks with EGR, which increases the cost. But the good thing is that the price of urea is not as outrageous as the price of oil, these expenses can be accepted.

The EGR is a component mounted on the valve cover of the engine that looks like a box overall. The box is a sandwiched hollow structure that is able to circulate antifreeze through the sandwiches, and the hollow structure allows engine exhaust gases to pass through.

After passing through the turbocharger, the exhaust gases are divided into two paths, one of which is discharged directly into the aftertreatment for treatment, while the other will be cooled by the EGR to reach a temperature relatively balanced with the atmospheric temperature. The mixture of fresh air re-enters the engine for secondary combustion, reducing the NOx content of the exhaust gases again and discharging them into the aftertreatment.

Engines using EGR have purer exhaust gases after combustion, less stress on aftertreatment, and less urea usage.

The downside is that EGR has more mounting parts on the engine body than high efficiency SCRs and the failure rate can be relatively high. Especially in extreme cold weather conditions, some EGR systems may leak. However, with the continuous upgrading of technology, there is no need to worry about the reliability of EGR technology. Normal use can basically do the same life cycle as the engine.