Def fluid
Have a 2011 Duramax. Have had a sensor problem. Dealer says the def from Walmart is giving some problems. Any thoughts.
Forum Discussion
jplante4 wrote:
DEF is different from DPF. With the particulate filters (2008 thru about 2010), they increased the exhaust gas recirc and filtered out whatever didn't get re-burned.
DEF uses a catalytic filter and the DEF fluid to wash the particulates out. The EGR rate was reduced.
People who know and people who have owned coaches with both technologies say that DEF is a great improvement. At any rate, if you look at a graph of gas vs. DP class As, the turning point was when the government got involved.
well, not really correct:
DEF and DPF are used to reduce emissions, and each performs a different function, true.
DEF is used to reduce NOX, not really any direct effect on particulates. urea combined with NOX to yield N2 and water. doesn't really do anything for soot. but it does reduce the need for EGR which is and has been and is used to reduce NOX emissions.
And EGR isn't real good for performance or economy, and is problematic in operation as well. Navistar tried using EGR only to control NOX emission in class 8 engines. pretty much bankrupt them, and ran into troubles with EPA. Never could get it to work well enough.
I'd rather have urea injection for NOX emissions and limited EGR and deal with urea injection issues if they arrise.
DPF uses a turbine flow to trap soot. like the old oil bath air filters. then once the filter gets to a certain soot level, extra fuel is introduced and burned, to increase the temp in the DPF to burn off the soot. In the current duramax there is a 9th injector in the exhaust header to inject fuel into the exhaust stream and raise the exhaust temp high enough to burn off the soot, basically carbon from the DPF.
DEF is constantly being injected into the exhaust stream, roughly 1 gallon of DEF for every 100 gallons of diesel fuel.
Since the DPF and DEF and cat converter are used to meet emissions, both systems should be covered for 100K miles or something like 8 or 10 years under the emissions warranty.
urea (DEF) is used extensively in many power plants to reduce NOX power plant emissions. Both in Coal fired and Natural gas fired power plants.
