Currently only smaller engines are EGR+DPF only. It takes having an SCR(&DEF) system to reduce emissions to legal limits on most larger engines now and the technology has been combined to have an engine with EGR+DPF&SCR(&DEF).
There are issues with engines and the active regeneration that has to occur in order to clean the DPF(basically engine has to get very hot and burn out the buildup) and also issues with DEF, which is an ammonia solution, both with the electronic dosing units failing and solution purity.
Here is a quick overview of how the system works.
Currently only smaller engines are EGR+DPF only. It takes having an SCR(&DEF) system to reduce emissions to legal limits on most larger engines now and the technology has been combined to have an engine with EGR+DPF&SCR(&DEF).
There are issues with engines and the active regeneration that has to occur in order to clean the DPF(basically engine has to get very hot and burn out the buildup) and also issues with DEF, which is an ammonia solution, both with the electronic dosing units failing and solution purity.