29/04/2025
Exhaust After-Treatment!
Some operators love to hate it. Yes, it can be problematic, but it performs a valuable task. Before you consider deleting the after-treatment components, consider the information below.
Some of you may be old enough to remember the days before emission controls: smog around the hills, and black Toitoi’s on the side of the motorway. Imagine those days with the number of engines we now have….
These are some of the factors to consider regarding exhaust after treatment:
NOx – what is it?
• NOx are oxides of Nitrogen.
Why are NOx bad for us and the planet?
• NOx contributes to smog and acid rain.
• When mixed with other compounds and sunlight they form ground level ozone – a major health hazard.
What produces NOx?
• Combustion of fossil fuels, particularly diesel engines.
What are we doing about NOx production from Diesel engines?
• Manufacturers have introduced exhaust aftertreatment systems to reduce the NOx production. These include EGR and SCR.
What is EGR?
• EGR stands for Exhaust gas recirculation. It takes some exhaust gas which has a low oxygen content and returns it to the engines intake system. This displaces some of the oxygen in the engines combustion chamber, lowering the temperature, resulting in less NOx production.
What is SCR?
• SCR stands for Selective Catalytic Reduction. It is a catalyst fitted to the diesel engines exhaust. Diesel exhaust fluid -DEF (commonly referred to as Adblue) is injected into the exhaust before the catalyst. A chemical reaction takes place reducing NOx close to zero parts per million.
The image below is a screenshot from Deutz SERDIA. It clearly shows 370ppm NOx before the SCR and 0ppm after.
Common Problems
• DEF has a limited shelf life. The quality of the DEF is measured by the system. If it is past its used by date, the system will not work.
• Turning off the battery isolator before the system has run through its shutdown procedure – it needs this time to empty the DEF lines to avoid crystallisation.
If you are having problems with your exhaust after-treatment, give us a call. We can walk you through some basic diagnostics first.
Happy breathing everyone!
www.shawdiesels.co.nz
0800DEUTZNZ
[email protected]
