More on the SCR system DEF Part two of two parts

As is usually the case in technical blogs, I'm not sure I made it clear that both Ford and Chevy are going to be urea consuming SCR systems on all their diesels.  So just sticking with one of them thru experience and brand loyalty will not get you the same truck or engine that you are familiar with.

Dodge on the other hand, is sticking with the exhaust gas recirculation technology of the past three years.  While you won't have to buy DEF and keep a fluid tank full in order to drive,  there are some major draw backs to staying in the EGR camp.

And it is worth noting that on their heavy trucks, they recognize that SCR is the way to go and add the system.  Are they just getting another few years out of the older technology in order to amortize their prior costs of research and development?

So I found specific arguments for each system out on the internet and will reprint them here.  From MHC Truck Source dot com.

"Selective Catalytic Reduction (SCR)  Urea injection

   It enhances thermal efficiency & fuel economy
   It reduces heat rejection and cooling system stresses, allowing for a
     smaller radiator and cooling fan and extending oil-drain intervals
   The smaller, lighter engine may equate to increased payload and less
     expensive (fuel) injection system.
   Can reduce emissions up to 90%
   Ideal where fuel economy and weight are primary considerations and
     trucks operate on main travel lanes.
   Availability of urea - searching for suppliers may add out-of-route miles
   Consumption of urea is unpredictable, since its mixing ratio varies with
     driving conditions.
   Vehicles will be fitted with a NOx sensor to ensure the urea level is not
     neglected. Failure to maintain the urea tank will result in a minimum 40%
     reduction in torque output if the additive runs out.
   The urea system cost doesn't really scale with engine size. It's a fixed cost
     and as you move down in engine size, it starts to account for a larger
     percentage of the engine cost.
   Least effective in stop start situations such as city operations where the
      constant acceleration creates the most NOx.
   Unknown price stability of urea.


Exhaust Gas Recirculation (EGR)

   Ideal for users running less traveled routes and those eager to avoid
     replenishing urea
   No additive, no extra tanks, and the loss of payload and fuel capacity
     associated with SCR
   No risk of experiencing a power down event due to NOx monitoring
   The addition of EGR coolers increases overall engine size and the
     additional heat loads could mean an increase of 10 to 30% cooling capacity
     might be required
   Technical risk related to the SCR catalyst and doser is eliminated.
   The simpler fueling requirements are easier for hired drivers, thus good for
     small-fleet driver retention.
   When combined with a DPF can reduce emissions up to 90%
   Engines are larger and possibly heavier, depending on power rating
   Larger radiator and fan are needed to handle small increase in heat
     rejection
   The fuel cost is higher than the cost of fuel plus urea in an SCR system."

As I understand this, with SCR we will be able to make more simple, smaller engines without all the pollution stuff added on.  They will get the fuel economy that they did years ago and not cost as much to run.  But, you will have to buy urea solution and maintain the injection system.  Urea is corrosive and has to be handled in plastic tanks.  And I'm sure will do nasty things to your exhaust pipes.  Also, it is fertilizer used in agricultural applications and has experienced massive wild price swings over the years that I was an agricultural accountant.  It could very easily cost twice or three times as much next year.

But using the EGR system causes us to keep getting bigger engines that can handle being suffocated with their  own exhaust being re piped into the intake.  This robs power and makes for inefficient fuel consumption.  So the engine has to be bigger just to make the same power as the little one did years ago.  (This is why Dodge Cummins went from a 5.9L to a 6.7L in 2007.)

I have read several places that the fuel economy of the non suffocated SCR engine will more than pay for the DEF you have to purchase.  Even create an overall savings in the long run.

Ya, maybe you can save some of that money to put on new tail pipes at the end of a year or two.

This stuff fascinates me  because there is really no good answer.  Experience will bear out the actual cost over time.  And as Rick pointed out in his comment, I'm not sure I want to be a first year purchaser of this system.  Who's to say they won't come up with an entirely different system next year and you'll be stuck with a white elephant when no one except you needs DEF. 

So for me, I'm not too sure I will trade my pickup until this all settles down some.  The motorhome is EGR, which means I am purchasing way more fuel to keep the pollutants in check.  So perhaps I am spending just as much, if not more and just have no way to measure it.

Only time will tell....

So why am I using this a a blog topic?  It is because I spent today getting ready to go over to my doctor's office, and sit in the waiting room until my blood pressure went thru the sky, and then go get it tested!!  Oh, its really that high?  Imagine that.   But I have been having indigestion problems, so lets hope they can solve some of it for me.

Somehow that doesn't seem like much of a blog topic.  But studying new diesel trucks is always fun for me!

Retired Rod

Urea! DEF! Part one of two parts.

I was over at our local Ford dealership yesterday, and noticed that there were a lot of white cab front truck chassis and bare frame trucks in their lot.  They evidentially have the contract to supply these vehicles to a body manufacturer.  This dealer has always had many all white trucks in inventory that will go to cities and commercial customers, so nothing is new.

But what did strike me, was the little Blue cap  on a separate filler tube for the 2011 model diesel trucks.  In a word "Urea" is here.  Oh my!  We ran into this on the motor home chassis down in Red Bay this spring.  Most of the newer chassis for motorhomes had Urea tanks.

Now what is this Urea thing all about?  Bring on the EPA and their new standards that took place in 2010.  They have turned down the amount of Nitrous Oxide that a vehicle can emit by about 80 %. Everything made after 2010 has to comply.

In Europe, they have been using urea injection into the exhaust of diesel engines for several years.  We are just now getting up to speed here in the US.  This urea product in Europe is called AdBlue.

I am not a chemist, and only understand the very basic concept of this, but adding urea in a 32.5 % liquid form into the exhaust stream at temperatures around 750 degrees causes a chemical reaction that changes Nox to Nitrogen and  Water.  Both perfectly harmless.

In the US we are going to know this liquid urea as Diesel Exhaust Fluid.  It is going to cost anywhere from three to five dollars a gallon.  Buy it at the truck dealer, and pay the most.  Once it becomes a standard thing, I'm sure it will get cheaper and be available everywhere.

Diesel Fuel still goes in back here.

DEF tank

This new Ford Truck had a small tank along the frame that contained this fluid.  It also had the machinery along with it to inject it into the exhaust.  They say you will refill this tank when you get an oil change.  The DEF will freeze at 15 degrees F, so part of the equipment on the tank would be a heater.

So how much of this stuff will the truck use?  I've seen estimates of 3 to 5 % of the amount of fuel used.  So use 100 gallons of fuel use 5 gallons  of DEF.  So add about $20 to the fuel bill for the 100 gallons.  Say $3 a gallon for diesel makes $300 + $20= $320.  So at 10 mpg pulling an RV that would go about 1000 miles. 

I looked on the Ford Vehicle web site to see if they explain any of this on their truck pages.  And no they don't.  They only say the new system is:

"industry-proven technology and Ford-designed innovations to meet the latest strict federal emissions standards, reducing nitrogen oxide (NOx) levels by more than 80 percent compared with the previous regulations."

What does that mean?  We aren't too proud of this new deal, but you have to buy it just the same!

Dodge  4dr 4500

So next just out of curiosity I went to the Dodge dealership.  And rode around on the bike until I found the Bare Chassis cab only trucks.  And there again was the blue filler cap.  These trucks were 4500 and larger series.  At Dodge, a salesman came right out and inquired what I was looking at.  I was taking pictures, and that always causes a reaction.

The Urea tank is up under the floor.  Dealer said it held 7 gallons.

Injection point in exhaust. Insulation keeps heat inside so reaction takes place.

So with a little conversation, I learned that only Dodges  4500 and over would use the DEF solution, and all of the 2500 and 3500 dually pickups will continue to use the catalytic converter system designed in 2007.  I have that system on my motorhome.  It is now substantially more refined from 2007 to meet 2010 standards and does not need DEF.

If you go look at the Dodge web site, they spend a lot of time explaining the fact that they meet the 2010 regulations without the use of exhaust fluids.  Unlike their competition.  The salesman was right up to snuff on this and made sure that I understood the entire concept.

So of course, buy a new Dodge pickup from us (Me) and be done with all this DEF discussion.

But if we are in the market for a new diesel Motorhome, or truck that is not a Dodge, or is heavier than a half ton in the case of Ford and Chevy, we will be using the DEF product.  The motorhome chassis we looked at in Red Bay had a 30 or 35 gallon tank right behind the right rear wheel.  Its going to take $150 to fill that one.

All of these engines had the new diesel particulate filter exhaust mufflers as well.  Particulate, is a nice way to say soot.  That eliminates the black part of the smoke.  So without soot and Nox, the diesel will be almost cleaner than a gasser!

Again I am an accountant, not a diesel mechanic, and this is just my understanding of the new technology, and may need corrected in part or totally.  So if you find an error in my thinking please leave a Comment!!!!!!

Also please comment on whether or not you are willing to purchase a truck or motorhome with these new innovations installed.  I'm not sure what choice we will have, but at least we can talk about what it will mean. 

Retired Rod