Diesel Emissions Control Systems – not a mystery anymore. And the results are tangible, both on and off road.
It may seem confusing, but it’s really just a particulate trap and a few chemical reactions.
DPF or Diesel Particulate Filter
A very poorly named device – it’s a trap, not a filter. Visible particles cannot get through this ‘filter’. If you see black smoke on a modern diesel, it’s either been illegally modified, or this ‘filter’ is physically damaged.
DOC. This is an actual flow through filter, containing precious metals to start the oxidation of hydrocarbons.
SCR. This is the piece that uses Diesel Exhaust Fluid (DEF), also known as Urea, to convert nitrogen oxides into nitrogen, water, and tiny amounts of carbon dioxide – all natural components of the air we breathe – which is then expelled through the tailpipe.
Care and Maintenance of this system – using the correct type and grade of engine oil is critical to proper system operation (and just good practice, too).
Many people are unaware that there is a filter in the DEF pump which needs to be changed at regular intervals too. Luckily, since Bosch supplies the majority of the systems in operation, there is one part number for the filter that fits almost 70% of the class 4 – 8 trucks in operation today.