How does DEF work and what’s the point of it? Why can’t it just be added to the diesel when it’s processed?
In: Chemistry
DEF is injected into your exhaust, not your intake manifold. If you added it to the diesel fuel it would be along for the ride as you go through your fuel pump, injectors, cylinder, combustion, and finally out through the exhaust. In a diesel truck the DEF reservoir feeds into the exhaust train upstream of your catalyst. It breaks down and makes ammonia and that combines with the nasty compounds in your diesel exhaust to produce nitrogen and water.
Combustion of diesel fuel produces nitrogen oxides and those are frowned upon by the EPA. DEF contains urea (yeah…you read that right) and that’s got ammonia in it. After injection into your exhaust the DEF becomes ammonia and isocyanic acid. From there the acid breaks down into carbon dioxide and ammonia. Those all flow through your catalyst and reduce the nitrogen oxides into nitrogen and water.
I copied this from another website so don’t think I just whipped this out off the top of my head, but the whole process is shown below. The goal is get rid of the 4NO.
2(NH2)2CO + 4NO + O2 → 4N2 + 4H2O + 2CO2 and 2(NH2) 2CO + 3NO2 -> 7/2N2 + 4H2O + 2CO2
Latest Answers