EGR White Paper

[DriVer]

Please review the the MaxxForce EGR vs SCR Technology white paper attached below.

Let's discuss ...
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[RustyJC]

Dueling marketing campaigns - HERE is Cummins' take on the issue.

Rusty

[DriVer]

Ok! .. So I'm still not liking urea and the MSDS says the stuff is toxic. Urea freezes? and if you're out or urea the engine runs at reduced power.

I'm reading that EGR doesn't have these types of issues.
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[Gary RVRoamer]

Obviously a system with no additonal fluids, tanks or delivery systems has less potential for problems than one with those things. Whether the SCR system with its DEF (urea) injection is actually a significant source of problems problem only time will tell.

The urea is DEF is toxic? Sure, but so is diesel fuel, ATF, antifreeze and most others fluids used in a powertrain. No need to be unduly alarmed here - urea is a common ingredient in the production of many medicines too.

[DriVer]

Quote:

Originally Posted by RV Roamer [Gary] No need to be unduly alarmed here -

Gary, I am unlikely to become alarmed. I'm just getting conflicting information from one source to another and I'm working through the challenges.

[Cruzer]

DEF (urea) is 37.5% ammonia and the rest water. Interestingly enough, Cummins' big 15 liter ISX does not use SCR, it uses A-EGR. The ISB/ISC/IAL all get SCR. The ISM gets dropped and replaced by a smaller version of the ISX, called the ISX-11. Don't know if the ISX-11 gets SCR or A-EGR though.

Personally, I don't like SCR. It just adds one more level of complexity. If it has no negative affects on performance or reliability, if it has a small (4%) gain in fuel economy, if the DEF isn't overly expensive and is an equal offsetting expense to the fuel economy gain - then you still have the hassle of having to obtain DEF and fill the urea tank up. You'll want to carry a few jugs with you too in case you can't find it when you need it. At 2 gallons of DEF per 100 gallons of fuel you'll probably need to do this every third tank fill.

Another concern I have is with the derating procedure built into the ECM. DEF freezes and you can start the engine and run it for a certain time with zero urea flow until the engine coolant loop warms the fluid up. In my neck of the woods I'd like to see how long that will take when it's zero degrees outside versus how many minutes it allows you to do that before the engine derates and is torque limited.

[Pusherman]

I agree with Cruzer regarding not liking the use of DEF in the new engines. It's just another thing to hassle with, it adds complexity to the engine (meaning potential problems) and expense...

I am very happy I have a 2007 coach with a 2006 model year EPA engine. No DPF regeneration...

My post on the 2010 EPA engines in the Motorhome General section was my intent to share what I learned from Cummins and Freightliner, as I know there are a lot of questions flying around regarding these new engines.

[RustyJC]

Although the DEF/SCR system does represent added complexity in the diesel engine system, neither is heavier dosing of EGR (the alternate approach to 2010 EPA emissions conformance) without its challenges and ramifications to maintenance requirements and costs. Each approach has benefits and disadvantages.

Rusty

[two2go]

Just wondering. Do the urea injection systems have some kind of smart detection technology built in? What's to keep one from putting in a gallon of supermarket cleaning ammonia?

[bstark]

I have read the SCR systems discussed on the pick-up truck forums are capable of detecting whether the urea is genuine or not. this was in answer to questions such as : "what's to stop us from filling the tank with water?"

So to surmise further; if Urea has a shelf life of about a year before it breaks down, and it can break down quicker if exposed to heat above 85 degrees or freezing temps, what will be necessary for all those who wish to use their RV to snowbird and simply drive it to one locate for a few months and then return it home where it will be parked for extended periods either local? One more PITA to have to drain a tank and discard unused portions due to age then re-fill with current supply.

That temperature of over 85 degrees would leave me thinking that this stuff is going to be degrading and producing ammonia gas for the entire time a rig would be sitting or travelling in the AZ or Fla sun with underrbody temps being much higher nearer the road surface?

[Cruzer]

Quote:

Originally Posted by two2go Just wondering. Do the urea injection systems have some kind of smart detection technology built in? What's to keep one from putting in a gallon of supermarket cleaning ammonia?

The tecnology is smart. It won't let you dilute it, let alone replace it with something else - which may just damage things anyway becasuse it's not designed for it.

[Cruzer]

Quote:

Originally Posted by bstark .....So to surmise further; if Urea has a shelf life of about a year before it breaks down, and it can break down quicker if exposed to heat above 85 degrees or freezing temps, what will be necessary for all those who wish to use their RV to snowbird and simply drive it to one locate for a few months and then return it home where it will be parked for extended periods either local? One more PITA to have to drain a tank and discard unused portions due to age then re-fill with current supply. That temperature of over 85 degrees would leave me thinking that this stuff is going to be degrading and producing ammonia gas for the entire time a rig would be sitting or travelling in the AZ or Fla sun with underrbody temps being much higher nearer the road surface?

Yes, I read that too. It freezes at 12 degrees and shouldn't be exposed to heat over 85 degrees. It's hot enough parked in Arizona during summer but when running an engine I'm thinking that tank will get pretty warm because it'll be close to the engine.

I also saw how the ammonia is bad news for aluminum and carbon steel and will corode it. The tanks need to be either stainless steel or plastic. I wonder what natural expansion will do to these vented tanks when all that vapor gets outand around the steel in the chassis. I'm thinking this might be similar to the outgassing typical to wet cell batteries and causing coroded battery terminals.

[jim and di]

In Power generating equipment we use both, gas recirculation is the least maintenance, however, not fool proof. SCR have challenges. Get the catalyst to hot and it will turn to kitty litter. My guess is if you dump in Ajax or some substitute you will end up replacing the catalyst which won't be cheep.
Kind of makes gassers look better.

[rops]

I predict Urea added for diesel engines will not last very long. I saw that the new Cummins engine used on Tiffin Motor Homes with the urea addition was going to cost approx $17,000 extra plus aggravate with adding Urea. Give me a break. Cummins doesn't drive consumer demand. Dollars and convenience do. And I assure you Cummins and any other manufacturer will change technology to sell engines. People are not going to line up to buy any engine that has the aggravation of adding urea to run the engine plus the added cost to go with that engine. If Navistar engines are efficient they will take over Cummins diesel business if Cummins stays on the urea kick. I don't know what motorhome buyers will do. I do know for a fact that truck fleets and Ag and heavy equipment people are not going to go with the urea trap if they have a financial alternative. Running equipment all the time has enough problems without adding the insanity of adding urea and maintaining the extra equipment just because a company was good in the past. Just look at how Toyota changed the car market if you think I am off base.
Also note Caterpillar and Navistar have entered into an agreement for Navistar to produce Cats 15 Liter engine with Navistar technology. The hand writing is on the wall regarding Urea in diesel engines and the horse race hasn't gotten to the first post yet.

rops