Mile High wrote:
So DEF is consumed if when not in Regen?
Yes. There's a typical EPA story here. They mandated a reduction in NOX which was met by recircing the exhaust gases like they did in cars in the 70s.
This in turn decreased the exhaust gas temps (EGT) and cause some unburned fuel to get passed through which caused diesel particulate matter (soot). The DPF removed the soot, but increased the NOX. Injecting DEF allowed the builders to cut down on the amount of recirc and increase the EGTs to reduce the soot and turning the NOX into water and N2,
The DPF and the SGR (where the DEF is injected into) are separate chambers that look like mufflers.
DEF is injected all the time. Regen increases the temp of the exhaust to "burn" off the soot in the DPF.
Confusing enough?