I just towed a large 5th wheel RV from SLC UT to North Dakota.

878 miles up and didn't see one regen the entire trip.. In fact watching my Edge CTS, I was seeing the Soot percentage drop to as low as .90 while I was towing. It never got above 1.20 during the tow. For reference, my truck right after a regen is usually around 1.15 and goes into a new regen around 1.75 to 1.85. So heavy towing and Passive Regen was cleaning my DPF better than a Active Regen.

While towing, my EGTs ran about 750° on level ground and climbed to 900° on steeper grades. I noticed the soot levels seemed to drop when the engine was just humming along at 750°. When I'd encounter a grade and the tranny would downshift and RPM would jump and EGTs would jump. the Soot concentrations would begin to climb. That conincides with my old memories of seeing clouds of black smoke from diesels when drivers would romp on or floor their trucks. So my thoughts are that the Passive regen will reduce soot if the engine is running hotter but on the lean side. Higher EGT temps from fllooring probably produce more soot due to the richer fuel load than the Passive regen is able to process.

Driving back to Utah empty with no trailer, I had one regen in the 875 miles. EGT temps stayed in the 525-575° range for normal freeway cruising. Which apparently is not hot enough for the Passive regen to work. Soot levels slowly climbed while driving at empty cruise speeds. The occassional grade climbs would see a small reduction in Soot levels if the truck stayed in 6th gear and just lugged up and over the climb. Forcing downshifts and faster RPMS again produced soot faster than the passive regen would process.

The drive up towing the large 5ver resulted in 9.8 mpg and the return empty trip got 17.8 mpg. Winter blend fuel. Temps on the trip up were in the mid 30's and the return trip was much colder with some stretches as cold as 15°

 

I wouldn't call those observations "Random". They are well thought out and include some great data.

Reps sent!

 

That is exactly the kind of behavior I have experienced also watching my Edge CTS (and of course, after the exhaust pressure fitting was properly re-installed). As long as I can keep the exhaust temp above 700 degrees on my chassis-cab exhaust configuration (DPF and SCR sequence reversed), the particulate loading stays low or drops close to 1 or less. However, it will still "force" a regen (even at particulate loading values below 1.5) at almost exactly at 620 miles after the previous regen. I wonder if this is one of the many differences between the chassis-cab configuration (California clean-idle certified) and the pick-up truck configuration.

 

Great info PH. Interesting to note that the active regen doesn't do as well as passive regen with a load and a lean foot. It would be great to have some fuel monitoring during those times. With the DPF back pressure reading .90, that would have be as free and easy as the stock exhaust gets. The only way to get a less restrictive DPF would be to remove it.

 

Good observations and detail. This is what I would expect.

The only difference I see for mine is active regens begin at 2.66 every time.
Also, at 575° empty, my soot count will remain the same or goes down (passive regen) but only very slowly.
This is why if I'm close, say 2.40's I can't get the darn thing to regen on the interstate and is why it will regen on Monday around town after weekend travels.
BTW - 1,400 RPM high idle will produce quite a bit of soot, if anyone was interested to know that.

 

A diesel that is worked hard will have less problems than a diesel that is a grocery getter. I think these "stats" prove it. Like crazy said, I'd call these more than random. Nice work!

 

I agree


Good info painted. Is similar to what I have seen! Or should I say haven't seen. that is- Not many active regens towing

Cheers