[Cngcummins]

I have studied about everything available on the internet about regeneration, but what still seems unclear is the exact algorithm that determines a regen. We know that the soot load percentage is based off readings from pressure sensors and EGT sensors, but I still do not understand what the algorithm is from those sensors. If anybody on this forum has an in depth knowledge of regeneration, I would love to get a discussion going with you.

 

[Snofarmer]

PSI differentiation of dpf suggests a soot load, regen.
no soot load, no regen.
Then there is also a timer that will trigger a regen regardless of soot load.

temp probes also will watch the heat. If it starts to get to hot it will scale back, and if it is to hot no regen will occur.

 

[Cngcummins]

to give you a little background, I own a Cng conversion business. We have started to do diesel dual fuel conversions, but one thing I noticed is that when we hooked up the Cng it would cause much more frequent regens, despite having a much lower pressure differential. So I believe it may also be looking at the other sensors to determine regen. I do understand there is a timer as well, but I was getting regens every 20 miles despite a much lower pressure differential.

 

[Snofarmer]

The rest of the story would have been nice in the first post you made.
you sure left out the crutch of your situation...

 

[Ram2012]

When used for short trips around town it goes into a sort of semi-permanent regen where it always tries to finish the cycle but doesn't have time before you shut it off and then it restarts from the top when you fire it back up. You might try running on the freeway for a hour or so. Even better if you're pulling something heavy.

There is a timer too but I'm not sure what it's exact schedule is.

The solution is pretty simple but you probably want to keep everything DOT legal for your business...

Seems to me CNG would burn a lot cleaner and clog the DPF less requiring fewer regens but who knows? :confused013:

 

[Cngcummins]

Sorry just didn't want it to come across as spam. I have a feeling that it may be using the nox sensor to look at stoichiometric ratio, and if it thinks it's too rich then it regens. However that is just a hunch, so if anybody can confirm that it would save me a headache. It is important to understand that we have tested soot load on a deleted truck with and without Cng and it was significantly less with cng

 

[yfz350guy]

Cng burns cooler as it has far less btu/lb compared to diesel, I'm being regens are being commanded by the pcm because of lower than normal exhaust temperatures, to control emissions the system needs to be hot. Watch the egt sensors in the exhaust stream with a scan tool while running on diesel then swap to Cng and I'll bet they cool down.

 

[Cngcummins]

It is true that CNG burns cooler, but when we are injecting it simultaneously with diesel at a 50/50 ratio we are seeing slightly higher temps, because the Cng creates a more complete burn of both fuels. Typically we see about 50 degrees F hotter temps on the egt sensors.

 

[yfz350guy]

It is true that CNG burns cooler, but when we are injecting it simultaneously with diesel at a 50/50 ratio we are seeing slightly higher temps, because the Cng creates a more complete burn of both fuels. Typically we see about 50 degrees F hotter temps on the egt sensors.

Very interesting, what are the delta values on the pressure sensors. Wonder if the increased burn efficiency is causing more exhaust pressure, or if the added cng is causing the soot built up in the exhaust to break free causing lots of regens sort term but may clean up long term.
How long have you been testing on this vehicle?

 

[Cngcummins]

The pressure values on the cts monitor are consistently under 2. We have considered that itay have been freeing up soot but we have run it for several thousand miles. We have a new system we are installing right now that actually has its own o2 sensor to keep correct fuel delivery in real time and we are hoping that will resolve the frequent regen issue. Do you know if the nox sensor plays a role in regen?

 

[Jeffs64]

Cng

BTW what is the increase fuel economy with dual fuels ? I know it's off topic but just wondering. Thanks

 

[yfz350guy]

Nox sensor should just verify the nox filter is operating, I don't believe it has anything to do with regen.

 

[yfz350guy]

By under 2, is that under 2:1 ratio or under 2psi? Most trucks I work on have less than 1.5 psi at wot if the filter is empty, if full highest I've seen is 10psi.

 

[Cngcummins]

Fuel economy is slightly better but the savings come from displacing a $3.90/gallon fuel with a $1.60 fuel at a 50/50 ratio. Essentially it brings your cost per gallon of fuel down to $2.60. There is also a horsepower gain and of course its cleaner and more efficient.

Regarding pressure differential: we typically hovered around 2psi with the Cng on, so substantially lower than what would determine a regen. That is why I believe that pressure differential is not the only variable for the regen process.