The truck will tell you if it needs a highway run to clean the DPF, so don't worry. Also, if you're thinking 2011, regenerations are much less often than on the 2007 through 2010s because of less exhaust gas recirculation.

 

Perhaps someone will correct me if I'm wrong, but the reason there are fewer regens and less egr is because the fuel timing is advanced to optimum. Before, it had to be backed of to prevent nox, but with the urea removing the nox they can tune the engine for the best possible combustion.

This is part of the reason there were milage gains in the past when adding a tuner--we modified the timing for more complete burn which gave more power without adding more fuel. If I'm understanding this correctly, there will now be very little to be gained economy wise when adding a tuner.

 

I just tried to find the link to the combustion description article I read about this issue, but the link now leads to a different article, so I can't yet "prove" what I'm about to explain, but I'll keep looking.

The way it was described in the article, in the 2007 to 2010 models reductions in NOX were achieved by recirculating some of the exhaust gasses back through the engine. This deprived the engine of some of the oxygen needed to create the NOX, and also produced more soot as a result.

It is interesting to note as an aside that Dodge has chosen to meet the 2011 emissions standards not by reducing exhaust gas recirculation and adding urea to kill the NOX, but by INCREASING the amount of exhaust gas recirculation to further reduce the NOX created at combustion. Time will tell whether it is a good strategy to feed even more soot laden exhaust gasses through their engines.

Reducing the amount of exhaust gas recirculation, as GM has done, allows more outside air into the cylinders, providing more oxygen for combustion, hence more power, plus less soot. The end result is higher mpg and fewer regenerations.

 

Hey Ted,

I think we may be both describing various aspects of the same thing.

Any way you look at it, less soot in the engine and more air has got to be better in the long run.

 

Agreed !!!

 

The 2011's will cycle through regen at 700 miles. There will not be a indicator telling the driver it is going through regen just like the 07-10's (bummer). It uses DEF to do the regen and not diesel fuel like the current models which is one reason it gets 11% better fuel economy.

 

The 2011's will cycle through regen at 700 miles. There will not be a indicator telling the driver it is going through regen just like the 07-10's (bummer). It uses DEF to do the regen and not diesel fuel like the current models which is one reason it gets 11% better fuel economy.

Negative on the last part.
DPF regens are still accomplished by squirting diesel into the exhaust. GM did get smart enough to add a 9th fuel injector on the LML's that opens straight into the exhaust; rather than just spilling extra diesel into the combustion chamber during the exhaust stroke like on the LMM's.

DEF or urea is injected as a fine mist into the exhaust ALL THE TIME. Only exceptions to this are frozen urea tank and/or lines.
DEF is responsible for a > 60% reduction in NOx from these engines, and allowed engineers to produce more power cleanly, and more efficiently. LML's get ~11% better economy than LMM's in spite of almost 100 ft/lbs more torque.

DPF reduces particulate emissions by 85-100%, at the cost of ~3% fuel economy loss on LMM's and < 2% fuel economy loss on LML's

 

I must have been mistaken. The interview I saw with the product manager I thought he said that they used the DEF instead which now that I think about it doesn't even make sense. Sorry for the bad information.