So I've enabled the DPF display using FORScan. The truck's very first regen took the expected 20 or so miles (it was nice to see he DPF % Full drop: 100, 95, 90, ... all the way to zero).

The second regen took all of about 3 miles. The % Full display dropped so rapidly it was skipping the 5 percent intervals.

What did I see? I'm anxiously awaiting the next regen!

 

No... the long regen was an Active regen. The short, a passive regen.

 

Very interesting. It was highway driving both times, unloaded.

 

Definitely a passive regen. When the truck senses ability to keep the filter clean instead of dumping fuel and a full blown active regeneration, it will perform short passive regens. What's interesting to me is that you saw a message. Usually, at least with my 2013, passive regens never displayed. Only my ScanGauge would detect them.

 

I dont beleive its a passive regen. My truck has done 2 of those since new. I have no explanation for it whatsoever but I think a few others have noticed it too. Passive regen would need to be above 750 degrees towing, mine did it both times on the interstate empty, takes about 4 minutes, goes from 100% to 5% in a heartbeat instead of the normal 15 minutes. Im beginning to learn the regen parameters for the 17 more as I go, it is tricky.

Ive noticed 8.38 is the soot gpl regen regardless of dpf %. The normal is 100% regardless of gpl (unless at 8.38 first) like clockwork. Ive also noticed in a passive regen, your dpf% will drop but your soot level will climb. I know this sounds wrong but I just experienced this last weekend. I started a thread on it last week because I thought I was getting bad readings but as I have driven since towing, things are falling back into normal order.

Case in point, I towed 2 hours each way, both trips the % dropped ,gpl rose. When I drove to work the next day it was at 33% but gpl hit 8.38 and regen started and I was at 400 miles since previous regen so the 500 mile thing dont apply. Now the % is creeping up compared to normal, gpl is climbing as always. My conclusion is a active regen just keeps the truck happy and running, a passive regen cooks it out completely.

My truck this regen will hit the 8.38 mark before it gets to 100% and I gurantee it will regen. If you tow alot its going to rely on the gpl level, more of a daily driver it will follow the %. When im not towing for awhile it hits 100% in the 5.5-7.5 range so it regens by the %. I was always under the impression if you tow alot it will never have an active regen but it appears that is not the case.I will monitor it, should be coming up next week sometime and report back.

Just my observations, hope I didnt clutter things up.

 

When the truck goes into regen cycle, how will I know? I have never seen anything on the dash displayed and I have roughly 1K miles on the odometer.

Someone please explain regen to me as well. I came from a 7.3.

 

Nothing shows on the dash in the 17 to indicate a regen is in progress unless you have the operator commanded regen option where it will ask you to start one. As far as knowing when one is in progress just watch live fuel mileage, when it starts plummeting one is in progress, or you can add the DPF % screen to the dash with forscan

In active regen
When the computer senses the pressure in the DPF rise to a certain point it interprets this as the filter filling with soot. When it senses the engine is at normal operating temps it will command the #8 injector (I think) to fire on the exhaust stroke to dump raw fuel into the exhaust that will ignite raising the temps in the DPF to burn off the soot.

In a passive regen generally you are towing and exhaust temps are high enough to burn off the soot naturally.

 

Will it produce an odor in the cab? Sometimes I have a smell of plastic burning but it goes awaway a short time later.

 

The first few can as all of the “new” is burning off, I am just about at 20k and don’t smell anything anymore.

 

The older 6.7 used one bank for regen. Updated software in 15 and 16 used both banks.
Pretty sure the 17 uses both banks for regen.

 

I thought mine was on fire the first time I caught a whiff of it. I have 5,000 miles on the odometer now and it smells like burnt cookies. The stink is just about my only complaint.

 

To be a little more precise, the truck doesn't actually "DO" a passive regen. That happens naturally when exhaust temps in the dpf reach a certain temperature and the particulates begin to burn away without any assistance. Passive regeneration happens when towing or otherwise working the engine harder than normal city driving. The regen strategy on my 2017 is very different than my 2011. An active regen on the 2011 would take about 10 minutes to complete whereas the 2017 takes about 35-40 mins from start to finish. Passive is different as well. The dpf on my 2011 would actually decrease in back pressure when towing and keep itself clean whereas the 2017 has never been able to reverse the particulate percentage by itself. It just climbs much more slowly when exhaust temps are up in the 750-800 degree range. When I'm towing I can go 400 miles in between active regens but if I'm driving on city streets it will go 150 miles between regens.

As for the dpf fill percent reading dropping quickly, I've seen that too. I've noticed that if an active regen starts say 5 minutes before I stop, the dash and PID will report the dpf fill percent at about 95%. But when I get back in the truck to go again it might be 40% indicating that the short little regen did more cleaning than it thought or the sensor is not very precise. Regardless, it is interesting but there's not much you can do about it. The truck will regen when it needs to and it seems to work pretty well.

 

Nice writeup Epic, my truck behaves exactly like yours only my active regens average in the 15-20 minute range. Been looking for a verification of what I have seen with mine, thanks.