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Generic question about Urea/DPF vs DPF only

8K views 6 replies 5 participants last post by  todt061458 
#1 · (Edited)
First, i'll preface with yes, i'm new, so i appologize for simple questions...

Now, i'm not trying to start a debate over brand X vs Y vs Z or anything, but asking about the basics of the systems themselves as it relates to the on associated parts and systems and overall long term reliability.... so, on to my question...

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.

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....

Thanks for any info..... and agian, this is not meant to be a "mines better" flame-a-thon.......

*waits for spears fly at the new guy......
 
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#2 · (Edited)
Ford And Gm are using a similar system of DEF/urea injection and Chrysler doesn't have DEF on non-chassis cab trucks, so there isn't a mines better than yours thing going to go on. While using DEF would allow for less restrictive DPF's, Ford, Gm and Chrysler will use the DPF's they currently have engineered. Ford and Gm will use DEF/urea to reduce emissions farther in combination with their DPF's. Ford is coming out with a turbo that incorporates an EGR on the new 6.7L using more EGR instead of less, while GM and Chrysler use the same amount of egr on they've had for a while. As for the operational range of DEF/urea I don't know what it is.
 
#3 ·
so, would/could there be more issues with the DEF for a vehicle that would see operating conditions vary all year from the heat to the very cold? what effect would those cycles have on the DEF in the DEF tank?

From what ive read, it says that as the DEF breaks down (mainly in high heat conditions) it turns into ammonia and water. does this ammonia escape the tank or what happens to it? If the DEF completly freezes, will the vehicle be stuck in limp home mode until it has idled long enough to sufficiently heat the DEF so that enough is usable for the vehicle to drive and operate?

Sorry if i'm asking so many questions. just trying to get informed as i'm looking to pick up a new diesel in the near future and want to make sure that i know what im spending my ~$50,000 on....

thanks for the input guys.... much appreciated......
 
#4 ·
This might help.
http://www.cumminsfiltration.com/pdfs/product_lit/americas_brochures/MB10033.pdf
Q. What is the freeze point of DEF?
A. A 32.5% solution of DEF will begin to crystallize and freeze at 12 deg F (-11 deg C). At 32.5%, both the urea and water will freeze at the same rate, ensuring that as it thaws, the fluid does not become diluted, or over concentrated. The freezing and unthawing of DEF will not cause degradation of the product.
Q. Does DEF expand when frozen?
A. Yes, DEF expands by approximately 7% when frozen. DEF packaging and tanks are designed to allow for expansion.
Q. How much does DEF weigh?
A. DEF weighs approximately 9 pounds per gallon.
Q. How do I keep the DEF from freezing? What happens if the DEF freezes in the tank on the vehicle?
A. During vehicle operation, SCR systems are designed to provide heating for the DEF tank and supply lines. If DEF freezes when the vehicle is shut down, start up and normal operation of the vehicle will not be inhibited. The SCR heating system is designed to quickly return the DEF to liquid form and the operation of the vehicle will not be impacted. The freezing and unthawing of DEF will not cause degradation of the product.
Q. Can an anti-gelling or freeze point improver be added to the DEF to prevent it from freezing?
A. No. While an additive could improve freeze point of the mixture, the 32.5% solution is very specific to providing NOx reducing properties. Any further blending or adjusting of the DEF mixture will impede its ability to perform correctly and may cause damage to the SCR components. Additives of any type are not approved for use in DEF today. If the ISO standards should change to allow antifreeze additives, Cummins Filtration will ensure our product continues to meet ISO requirements.
 
#5 ·
Thanks for the info Josh
 
#6 ·
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.
 
#7 ·
So if it is 112 degrees outside real temp my def fluid eill start to degrade? did I read the right? why would I want that. I travel alot through
N Dakota in the winter So I should expect my fluid to freeze over night while the truck is shut down? thank you EPA.
 
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