DPF Equipped Engine - Best Operating Practices

[Frank McElroy]

With all the recent discussions on DPF issues and after talking to a few folks offline, I realized that what I thought was common knowledge about how to operate an engine with DPF actually wasn't known.

So, I thought it would be a good idea to start a topic on what I consider are the best practices in how to properly operate a Cummins engine equipped with a Diesel Particulate Filter (DPF).  Many of these also apply to other diesel engines but I'll focus on engines with DPF.

First and foremost, please read the section in the owners manual covering extended idling and full throttle long hill climbs.  For reference, I posted a picture from page 21 in my 2008 Dynasty owners manual.

When starting the engine, after about a minute, turn on the cruise control and press "set" to run the engine at 1200 RPM fast idle.  The engine needs to get the DPF hot as soon as possible.  This engine has a fast warm up operating mode that actually puts load on the engine when running above 1000 RPM.  This will get the DPF hot in the shortest amount of time.  When running fast idle, take a look at the engine Load on the LCD screen.  you will see about a 20% engine load.  The engine is adjusting fueling and VGT parameters to generate about a 20% load to quickly heat up the DPF so that it can work faster.

When climbing grades, I do NOT recommend using the cruise control.  Nor do I recommend climbing long grades at full throttle and letting the transmission select the gear.  The best way to climb a long grade is near the max HP and on the ISL that's about 2100 RPM.  So, manually gear down, keep the RPM up between 2000-2100 and climb the grade with the throttle just short of full throttle. This will put a lot less load on the engine vs full throttle and climbing at highest gear. You will be putting out less soot and the turbo will run a lot cooler.  Don't worry about exceeding the max 2200 RPM, the engine won't let you do that.

I've said this before but I should repeat it here.  When the DPF light comes on, it is telling you to drive the coach under conditions to allow a DPF regeneration.  That means highway speeds in the low 60's.  The following operations will suspend the regeneration cycle - using an engine brake, speeds below about 35 MPH, coasting down hill, full power climbing a grade, almost any time the check engine light comes on.  Sometimes these can't be avoided - so the regeneration cycle might take a little longer to complete.

While driving on the highway, the DPF is hot enough to be doing passive regenerations.  So the pressure differential across the filter stays low enough to not trigger an active regeneration.  However, over about 100 hours of engine key on time passes, the ECM will do an active regeneration.  The light will come on and last about 30 minutes.  If you are starting to see regenerations after say every 40-60 hours, it's time to find out why you are generating soot.  At a minimum, have a shop connect Cummins Insite to the engine ECM and look at the last 10 regenerations to see if there is a problem developing.

It is very important to resolve any check engine light issues.  In almost all cases a check engine light will suspend a DPF regeneration.

Periodically, the DPF light might come on for just a few minutes and then go out.  All this means is that the pressure differential was high enough that an active regeneration might be needed but the passive regeneration took care of it. 

I hope this helps others with DPF coaches learn more about how to drive them.

 

[Tom Cherry]

11 hours ago, Frank McElroy said:

With all the recent discussions on DPF issues and after talking to a few folks offline, I realized that what I thought was common knowledge about how to operate an engine with DPF actually wasn't known.

So, I thought it would be a good idea to start a topic on what I consider are the best practices in how to properly operate a Cummins engine equipped with a Diesel Particulate Filter (DPF).  Many of these also apply to other diesel engines but I'll focus on engines with DPF.

First and foremost, please read the section in the owners manual covering extended idling and full throttle long hill climbs.  For reference, I posted a picture from page 21 in my 2008 Dynasty owners manual.

When starting the engine, after about a minute, turn on the cruise control and press "set" to run the engine at 1200 RPM fast idle.  The engine needs to get the DPF hot as soon as possible.  This engine has a fast warm up operating mode that actually puts load on the engine when running above 1000 RPM.  This will get the DPF hot in the shortest amount of time.  When running fast idle, take a look at the engine Load on the LCD screen.  you will see about a 20% engine load.  The engine is adjusting fueling and VGT parameters to generate about a 20% load to quickly heat up the DPF so that it can work faster.

When climbing grades, I do NOT recommend using the cruise control.  Nor do I recommend climbing long grades at full throttle and letting the transmission select the gear.  The best way to climb a long grade is near the max HP and on the ISL that's about 2100 RPM.  So, manually gear down, keep the RPM up between 2000-2100 and climb the grade with the throttle just short of full throttle. This will put a lot less load on the engine vs full throttle and climbing at highest gear. You will be putting out less soot and the turbo will run a lot cooler.  Don't worry about exceeding the max 2200 RPM, the engine won't let you do that.

I've said this before but I should repeat it here.  When the DPF light comes on, it is telling you to drive the coach under conditions to allow a DPF regeneration.  That means highway speeds in the low 60's.  The following operations will suspend the regeneration cycle - using an engine brake, speeds below about 35 MPH, coasting down hill, full power climbing a grade, almost any time the check engine light comes on.  Sometimes these can't be avoided - so the regeneration cycle might take a little longer to complete.

While driving on the highway, the DPF is hot enough to be doing passive regenerations.  So the pressure differential across the filter stays low enough to not trigger an active regeneration.  However, over about 100 hours of engine key on time passes, the ECM will do an active regeneration.  The light will come on and last about 30 minutes.  If you are starting to see regenerations after say every 40-60 hours, it's time to find out why you are generating soot.  At a minimum, have a shop connect Cummins Insite to the engine ECM and look at the last 10 regenerations to see if there is a problem developing.

It is very important to resolve any check engine light issues.  In almost all cases a check engine light will suspend a DPF regeneration.

Periodically, the DPF light might come on for just a few minutes and then go out.  All this means is that the pressure differential was high enough that an active regeneration might be needed but the passive regeneration took care of it. 

I hope this helps others with DPF coaches learn more about how to drive them.

 

BRAVO…..Thanks for writing this.  If every person that has a DPF concern, curiosity or issue would read this, then they would be light years ahead and better able to understand the comments that many will make…  only one comment based on what you said..

Periodically, the DPF light might come on for just a few minutes and then go out.  All this means is that the pressure differential was high enough that an active regeneration might be needed but the passive regeneration took care of it. 

You looked at my ECM UPGRADE LEVEL (43] and that covers most of the “must do’s” that initially required to tweak the ECM.  I made the delivering dealer get them installed before I bought the MH (new) and I had the engine S/N and Cummins tech support told me that one was critical.  That was in January 2009.  Since then, Cummins has only serviced it once, circa 2013 to comply with the extended warranty so coolant and Allison was serviced.  I have no idea if Cummins updated the ECM, but I’ll do some digging and try to figure that out, now that I understand and have more info.

Your offline advice is that there are some, as expected, more revisions out there, but no really critical.  However, one may calm down the flashing REGEN light.  All my Regen history has been like clockwork at 100 hours and I have no lights and all seems well.  Therefore, I will get the ECM updated just to eliminate this nuisance.

ALL THAT SAID….Thanks for the post.  It is a good thing we don’t have stringent acceptance criteria….otherwise reading this would be required….if you register with a DPF…..LOL

[Patricia Ferrara]

Big thanks to Frank & Tom, for explaining DPF and Regen issues I terms that even I (brand new to Diesel Pushers) could understand! I am saving this information for easy access, should we need it in the future. Bravo!!!