Reliability of coaches using DEF

[midasman]

I have wanted to upgrade as my Holiday Ambassador is moving toward it's 10th year. How are people doing with the newer coaches using DEF? It's made me wonder if moving back to a gas coach makes more sense. Or, keeping and modernizing my diesel pusher. We do Ouray, Colorado every year which means pulling my Jeep Wrangler over the Million Dollar Highway, climbing higher than 12000 feet...

[JumboJet]

Regeneration occurs as either passive regeneration where the EGTs are sufficient to burn the particulates out of the DPF (Diesel Particulate Filter). This can occur under heavy load or during a long run. Active regeneration occurs when extra fuel is injected during the exhaust stroke and creates extra heat/combustion in the DPF.

On my 2014 RAM I can smell a regeneration when sitting still at an intersection or when I park the truck in my garage and hear the extra metal popping noises coming from the DPF.

[Mr_Mark1]

wildmanbaker wrote:

tyoungs wrote:
In general, when you can do the clean-up after the combustion process, then you can run the combustion for best efficiency and not lowest emissions. If you remember back in 1975, that was the first use of catalytic converters on gas engine vehicles. Everyone bemoaned having to use unleaded fuel but the 1975 vehicles with converters ran so much better and with such better fuel economy (because the converter cleaned up the exhaust "after" the combustion process)as compared to 73 and 74 that most people soon stopped complaining about having to use unleaded fuel.

Same with DEF, it allows the clean up to be done after the combustion process and with the advent of the digital controlled diesel injection, the engineers have much more control over every point of the combustion cycle. They can tune the combustion event for better efficiency and allow the clean up to happen in the exhaust after treatment devices. Lowest emissions in the combustion cycle and maximum efficiency in each cycle are usually not the same point.
If you have to "tune" the combustion process for lowest emissions with no after treatment, you generally are not at the point where you have max efficiency.

Not a very good comparison, unleaded gas to DEF. DEF does not harm the engine, unleaded gas was a BIG learning curve for auto manufactures. No one has mentions what happens when the engine control decides to go into re-gen, in the middle of a steep climb.

OK, what happens when it goes into regen on a steep climb?

We had the 2008 Dynasty for 7.5 yrs. and it would regen about once every 9,000-10,000 miles. Never noticed anything was going on unless I looked down to see the symbol lit.

We just went through our first regen on the new coach (11,000 miles). A message came up in the instrument cluster to let me know a regeneration was activated. Never noticed any difference in performance.

But, it never happened to us on a steep climb in either coach.

So, tell us what happens?

MM.

[silvercorvette]

When I bought my 2010 Dodge truck I chose Dodge because it was the only one that was not using DEF. I traded my Dodge for a 2014 Chevy that uses DEF. The dodge got about 10 to 14 MPG, My Chevy now gets 14 to 18 and I am guessing the DEF has something to do with the better MPG.

[wildmanbaker]

tyoungs wrote:
In general, when you can do the clean-up after the combustion process, then you can run the combustion for best efficiency and not lowest emissions. If you remember back in 1975, that was the first use of catalytic converters on gas engine vehicles. Everyone bemoaned having to use unleaded fuel but the 1975 vehicles with converters ran so much better and with such better fuel economy (because the converter cleaned up the exhaust "after" the combustion process)as compared to 73 and 74 that most people soon stopped complaining about having to use unleaded fuel.

Same with DEF, it allows the clean up to be done after the combustion process and with the advent of the digital controlled diesel injection, the engineers have much more control over every point of the combustion cycle. They can tune the combustion event for better efficiency and allow the clean up to happen in the exhaust after treatment devices. Lowest emissions in the combustion cycle and maximum efficiency in each cycle are usually not the same point.
If you have to "tune" the combustion process for lowest emissions with no after treatment, you generally are not at the point where you have max efficiency.

Not a very good comparison, unleaded gas to DEF. DEF does not harm the engine, unleaded gas was a BIG learning curve for auto manufactures. No one has mentions what happens when the engine control decides to go into re-gen, in the middle of a steep climb.

[tyoungs]

In general, when you can do the clean-up after the combustion process, then you can run the combustion for best efficiency and not lowest emissions. If you remember back in 1975, that was the first use of catalytic converters on gas engine vehicles. Everyone bemoaned having to use unleaded fuel but the 1975 vehicles with converters ran so much better and with such better fuel economy (because the converter cleaned up the exhaust "after" the combustion process)as compared to 73 and 74 that most people soon stopped complaining about having to use unleaded fuel.

Same with DEF, it allows the clean up to be done after the combustion process and with the advent of the digital controlled diesel injection, the engineers have much more control over every point of the combustion cycle. They can tune the combustion event for better efficiency and allow the clean up to happen in the exhaust after treatment devices. Lowest emissions in the combustion cycle and maximum efficiency in each cycle are usually not the same point.
If you have to "tune" the combustion process for lowest emissions with no after treatment, you generally are not at the point where you have max efficiency.

[midasman]

I'm impressed! Friend had Dodge 1 ton with 6.7. It STAYED in the shop. He used it for hot shot. Lost a TON of money waiting on Chrysler to try to figure out what was wrong!

[ScottG]

Thunder Mountain wrote:
We too are looking at a new coach as we are approaching ten years. One salesman told us the DEF engines actually get better mileage. Tell me if this is fact or just another example of a salesmen telling the tale to make a sale.

In theory it can be true.
It's because the DEF system works so well that they are able to put some of the timing and fuel curves back where they used to be when diesels got such good fuel efficiency.

[Thunder_Mountai]

We too are looking at a new coach as we are approaching ten years. One salesman told us the DEF engines actually get better mileage. Tell me if this is fact or just another example of a salesmen telling the tale to make a sale.

[phranc]

Considering the millions of miles put on by over the road trucks,
I would also say...A non issue ..

[Mr_Mark1]

We have DEF too, no problems in 11,000 miles. Had to learn how to operate the pump when using two different fuels. Piece of cake. LOL!

Don't worry about DEF.

MM.

[ScottG]

I have a neighbor who works where there is a fleet of medium duty trucks that use DEF. They are the most reliable trucks they have ever had.
As said before, DEF is a non-issue.

[sch911]

DEF has become a huge enabler for the engine manufacturers allowing higher combustion pressures, higher temperatures, and higher outputs (HP/Torque). With DEF they don't have to deal with the emissions side of things as much.

[rr2254545]

DEF is a non issue - we have 26K on our motor home. It is just to make the diesel have a cleaner exhaust