so, i read something on one of these pages (the exact thread escapes me) where someone had mentioned that the use of DEF (urea) in addition to the DPF would be better for the engine and economy/power vs. use of only DEP as the addition of urea would allow for less restrictive DPF's to still meet the emissions standards and the use of less EGR, so therefore, less soot being circulated back thru the engine....
can anyone enlighten me as to any of the validity of this? it seems to make sence to me that an engine would be able to be tuned better (ie, more useable power, better economy, and most importantly, improved reliability and longevity) by lessening the restrictions places on these motors and by lessening the the amount of EGR required.
That is, at best, wishful thinking.
At current market conditions, and for the forseable ones at least....
- DEF is MORE than disesl, a LOT more (like 2x-5x more $$$/gallon).
- For every gallon of diesel "saved" by using DEF, you will use a gallon of DEF (or so).
- Unless Disesl $ ~ DEF $, you will pat MORE per mile (DEF + Diesel Vs Diesel) to drive.
- Yes, SCR will allow manufacturers to meet strict NOx limits with current EGR rates.
- No, SCR will not allow "less restrictive DPFs", you are limited in the PM size emitted and the total per Hp-Hr, so the DPF remains essentially unchanged.
- I fail to see how added tanks, lines, wiring, heaters, a third catalytice converter and additional DEF injector can increase reliability.
- SCR will not produce any significant reduction in the need to regenerate except for vehicles operated mostly at light loads.
just trying to educate myself on the different aspects and pro's/cons of each system.
Also, does one system have a distinct advantage when it comes to climate varyances? ie, if a truck was going to be used everywhere from the summer southern desert climates (arizona/nevada/ect) all the way up to winter time nothern states (michigan, dakotas, colorado rockies). i know DEF has a freezing point somewhere around like ~5 F or so and from what i've read can be effected by high temps. how would frequent varrying operating locals' such as these effect the longevity of the motors/exhaust systems?
especially right now as i'm in the market to upgrade to my first diesel sometime in the next 6 months or so and am seriously eying some of the upcoming models....
DEF degrades at temperatures greater than 98*F and freezes at 12*F (or so). These factors are compensated for in vehicle design. SCR offers an advantage primarily in light load applications or applications where start-stop driving is required allows the use of higher EGT strategies in the ECM which limit soot production but increases engine-out NOx.