DEF re-gen cycle frequency

I can tell you that our old HR without DEF but had the DPF used to regenerate about once every 8000 miles or so and usually at the start of a season after being off road for 2 months in winter..You could practically set your watch by it and it would last 20 minutes...I have about 13000 miles or more (I honestly don't remember) on this coach using DEF and have yet to see a regen light, but 80 to 90 percent driving is all highway at my magic spot of 63 mph. I also really don't let it needlessly idle to build up the DPF.

moleary wrote:
We've owned our 2012 Winnebago Tour for 2 years and traveled roughly 15000 miles. We purchased it with 17000 miles. I have yet to experience a DEF re-gen cycle. Isn't there a dashboard light to notify that the cycle is occurring? Ninety percent of our travels are at interstate speeds and conditions(if that makes any difference). I thought it would have called for a re-gen at least once during this time.

Everything is running fine, just wondering why.

You've already been given the answers you need but since our coach is a twin to yours, I thought I would add simply that I've noticed the REGEN light flicker once for a few seconds on our Ellipse. I too was wondering if I would ever see it but sure enough, it actually did illuminate very briefly.

Had a regen last week on our long drive Westward. This is only the second one that I have seen on this coach and this one was at 42,000 miles. It lasted for about 30-35 minutes.

MM.

bullydogs1 wrote:
DEF has to be consumed all the time as it turns exhaust to water and a harmless gas...My regen light in my old coach used to go on about once every 5000 miles or so (once a year) and go off after about a half hour...Present coach has 10000 miles on it and it has not gone on once...Fuel mileage is better with the setup too..And although the door is on the right side..Im perfectly OK with adding the 2.5 gallon jug I buy and putting it in..not a big deal..The only coach I have ever seen with both the fuel door and the DEF port right next to each other is a Prevost...Even the driver side port for most coaches is on the rear of the coach...so you have to go back in and move the coach anyway.

jplante4 wrote:

Mile High wrote:
So DEF is consumed if when not in Regen?

Yes. There's a typical EPA story here. They mandated a reduction in NOX which was met by recircing the exhaust gases like they did in cars in the 70s.

This in turn decreased the exhaust gas temps (EGT) and cause some unburned fuel to get passed through which caused diesel particulate matter (soot). The DPF removed the soot, but increased the NOX. Injecting DEF allowed the builders to cut down on the amount of recirc and increase the EGTs to reduce the soot and turning the NOX into water and N2,

The DPF and the SGR (where the DEF is injected into) are separate chambers that look like mufflers.

DEF is injected all the time. Regen increases the temp of the exhaust to "burn" off the soot in the DPF.

Confusing enough?

And thank you gentlemen for the thorough explanations. I had a misconception of how that worked!

A Cummins rep responded to an email inquiry I submitted and confirmed what most of you have already explained to me. At least as far as my particular ISL engine is concerned, the re-gen process is usually passive, meaning it takes place without the operator's knowledge. The only time the operator may be alerted is when the engine is operated frequently at low speeds. Since most of my driving is interstate, it is unlikely I would ever know a re-gen is happening.

Thank you all for your replies.

Mile High wrote:
So DEF is consumed if when not in Regen?

Yes. There's a typical EPA story here. They mandated a reduction in NOX which was met by recircing the exhaust gases like they did in cars in the 70s.

This in turn decreased the exhaust gas temps (EGT) and cause some unburned fuel to get passed through which caused diesel particulate matter (soot). The DPF removed the soot, but increased the NOX. Injecting DEF allowed the builders to cut down on the amount of recirc and increase the EGTs to reduce the soot and turning the NOX into water and N2,

The DPF and the SGR (where the DEF is injected into) are separate chambers that look like mufflers.

DEF is injected all the time. Regen increases the temp of the exhaust to "burn" off the soot in the DPF.

Confusing enough?

DEF has to be consumed all the time as it turns exhaust to water and a harmless gas...My regen light in my old coach used to go on about once every 5000 miles or so (once a year) and go off after about a half hour...Present coach has 10000 miles on it and it has not gone on once...Fuel mileage is better with the setup too..And although the door is on the right side..Im perfectly OK with adding the 2.5 gallon jug I buy and putting it in..not a big deal..The only coach I have ever seen with both the fuel door and the DEF port right next to each other is a Prevost...Even the driver side port for most coaches is on the rear of the coach...so you have to go back in and move the coach anyway.

So DEF is consumed if when not in Regen?

11178adm wrote:
as stated in another post the DEF system does not regen but the diesel particulate filter (DPF) does. if the regen occurs when driving there is no effect on the engine operation and no indicator light unless the vehicles speed drops below about 7 mph during the regen then a high exhaust temp light will come on until the DPF and SCR catalyst cools down or the vehicle speed goes back up, if the high exhaust temp light is on it is a good idea to not shut the engine off until the light goes out. I am assuming it is probably a ISL cummins if it is next time you are in a cummins shop and they are plugged into the ECM ask them to print out the regen history, it might surprise you how often I happens.

Best answer. I've only seen the regen light once on our '16 Journey. That was in slow traffic. Went off when I got up to speed. Had to pull the manual a do some reading to find out what the light was for. Really didn't worry me since the light was not red.

Most vehicles will not let you know when regen is happening. If a light comes on, it is because you are past the normal point for a regen to take place. Lots of short trips or excessive idling can cause this. Sometimes once you get a regen to happen on its own the light will go off or if too severe, it may need software connected to it to get the light off. I have had trucks at my shop that would only run 5 mph because the soot level was so severe. This usually is caused by a bad sensor not letting the regens happen.

Regens will normally happen every 500-1500 miles depending on driving habits. The dpf can have a differential pressure sensor on it that actually determines the soot level or the computer monitors driving conditions and calculates soot level. Each way has good and bad factors. Your coach is doing its regens or you would know it by now. And as stated above, def has nothing to do with regens.