pure urea (the majority of the exhaust fluid) has a melting point of ~273 F
which means the systems employ a series of heaters to keep the fluid liquid (especially in cold times and in cold climates) (not just a tank heater but a line heater and injector heater)
The majority of it is Deionized water. 67.5%. The other 32.5% is pure industrial grade Urea, not fertilizer grade.
It freezes at 12*.
We have a fair number of Class 8 diesels with DEF in the fleet right now and for kicks and grins we tried 28%, the same stuff we put on Corn. It works just fine.
You must have one of the earlier trucks that a certain MFG didnt program the sensors properly and you could even run water in them. But maybe you dont I dont know.
Now you cant do that(maybe you can), the sensors will detect if it is not pure DEF.
DEF has a shelf life of 4 months-2 years. The deciding factor is heat. Over 86* and it will start to degrade. So make sure you only buy what you need and store it out of sunlight and in a cool place if possible.
Interesting. I Learn something new everyday. Things just tend to get more complicated. I wonder if they're do the same for tractors...
Yes they are, currently have one on the farm with it. All but Deere and Challengers larger tractors with CAT engines, have SCR.
my issue is, if they cant seem to fix a heater for something simple like WWF... what are the odds they can successfully design multipul heaters to keep the DEF from freezing and f'n everything up.
Um have you read the news? GM cant keep the DEF from freezing, they're having glitches left and right. hopefully they got it fixed this time though (update #20). Im a diehard Duramax Fan, but not afraid to admit their issues.
Now on the topic of DEF. The system is called SCR, Selective Catalytic Reduction.
Simply put it is injected into the exhaust at a variable rate to control NOX emissions. When injection it reacts in the catalyst to convert the NOX into water, Nitrogen and a trace amount of CO2.
NOX and particulates are the two to remember when it comes to diesel emissions.
There are currently 2 systems in place for reducing NOX.
EGR/NOX absorbing catalyst. and SCR. Both systems use Particulate filters for the particles but its important to look at how each system affects that pesky gremlin called the DPF.
The EGR based systems rely on creating colder combustion temperatures and recirculating large amounts of EGR. This creates a cooler combustion which results in less NOX. However anybody who payed attention in school knows that cooler combustion is more inefficient. Which holds true, with the cool combustion the particulates do not get burned which causes the DPF to plug up much faster than on an SCR motor. Also due to the cooler more incomplete combustion fuel efficiency suffers. In addition the added particulates in the system cause premature wear and require more frequent oil changes (Example is the 200hr OCI on the John Deere(EGR) versus the 600hr interval on the case IH (SCR)or 400hr interval on the Massey/Challenger(SCR))
The SCR approach relies on aftertreatment of the NOX. meaning they can tune the engine for maximum power, performance and efficiency and let the SCR system scrub up the large amounts of NOX later on. This also results in less particulates which means fewer regens, longer engine life and longer OCIs.
SCR also allows MFGs to use smaller engines to produce the power needed, again this goes back to the heat factor. Case IH is running a 12.9L In their biggest tractor (they used to run 15L) and are making 600ratedhp (SCR) and 670 peak hp. Challenger is using an 18L engine to make 585hp (EGR)
So is SCR new and not proven? NO!! Its been used at power plants and in Europe for a while.
SCR does have its downfalls though. The main one is the DEF itself. Its a pain to handle. Its mildly corrosive, makes a mess, freezes and doesnt last long. There are more solid solutions in the works though to replace it.
