Reliability of coaches using DEF

Tyoungs, I was responding to Wildmanbaker. I understand what you are saying.

MM.

Mr.Mark wrote:

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.

The point I was trying to make comparing unleaded fuel and catalytic converters on gas jobs, and DEF with Diesels is that both allowed the clean-up of the emissions to happen in a device after the combustion chamber. That in turn allowed the folks calibrating the engine to optimize the combustion process for power/torque/economy and not have to bugger up the combustion process to minimize emissions.

True that there was some learning curve with unleaded fuel (hardened valve seats and such) but that fuel allowed the use of the catalytic converter to do the major clean-up of HC and CO emissions. The side benefit was much longer life for spark plugs since you were no longer fouling them with lead.
Same thing with DEF, it lets you use an aftertreatment device to reduce emissions and the engine calibrators don't have to do all the clean up in the combustion cycle.

Oh, I guess I didn't answer the question. In limp mode, the ECM reduces engine power, and some times speed, until the regen is competed.

Well, most if the time, nothing. The regen is for the Diesel Particulate Filter. I'll admit, I have not messed with an RV with the new clean air requirements (2010 and later). Other diesels, usually have a 2 or 3 position regen switch for controlling the regen cycle. What this does is raise the temp of the DPF to burn the soot into ash by injecting fuel into the exhaust system. This happens more at colder temperatures, with extended idling. What happens if you plug the filter, or overheat the cat., contact your local repair shop for prices.

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.

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.

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.

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.

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.

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!