Regen - I'm ignorant

[KathyandDave]

Since we've had the Sierra, sometimes it would lose power, the speed would drop to 60km/h (35mph) and the RPM's wouldn't go higher than 2K. This seemed to happen after moderate hill climbing or stop and go traffic on hot days. The dealer said, "No codes, no problem", patted me on the head and sent me away. Now, finally, I've learned a little bit. It turns out that the regen is a computer-driven process to reduce the particulate ("soot") weight in a filter that's important to some testing required by some jurisdictions to transfer the ownership. Regens start on their own, without regard to the operation of the vehicle at the time. Apparently, we don't notice them if the vehicle is running at highway speed with no load, but pulling the MOnty is different. But, since the computer INCREASES the revs during the regen, which might be dangerous, the regen is cancelled if you touch the brake pedal. Also, the fan goes to maximum speed to cool the engine and transmission during the stressful regen, so we hear a loud fan roaring sound. In my case, I heard the fan, thought the tranny had overheated, so I touched the brake and pulled over to let things cool down. Unknown to me, the regen was then cancelled, but the particulate numbers continued to build, so the attempts by the computer to regen became more frequent. The GM diesel mechanic (at a different dealer) that finally understood my problem started the regen using the GM handheld computer that plugs in under the steering wheel. The count went from 38 grams to 9 grams of particulate, a big drop, since the motor had not likely successfully completed a regen for a long time. I watched the whole process. It took about 20 minutes. The regen made the exhaust system so hot that oil that had slowly leaked under the frame began smoking heavily. That became a repair bill for a leaky transfer case seal. The GM mechanic suggested I go down the street and get a chip that bypasses the regen, since the pollution test it satisfies isn't required to sell a vehicle in Ontario.
Now you know everything I know, which is almost nothing. I'd like to know what others know about this.

[DQDick]

Strange deals to meet emission standards aren't limited to GM. Dodge uses the heat in the exhaust to cremate the particulates. Last summer I was in the shop twice with the check engine light until they explained how it works. We were working for the COE and so the truck just moved around the park and seldom went over idle speed causing the equipment to gum up and turn the light on. They told me it was a big problem around here because the farmers using trucks to feed cattle never got the system hot enough and so they failed often. Having to take the truck out on the road several times a week would be a real PITA if I didn't spend most of my time in the boonies.

[grayghost03]

Generally, regen starts at normal operating temps and you need a sustained operation speed of about 55 mph or better for 20 to 30 minutes to start and complete a regen. If you do not complete the cycle it will start over on older vehicles, I know that the 2013 will pick up where it left off when temps and speed are met again. If you don't do a regen within a specific time frame(pressures are monitored on both sides of filter) and pressure variance grows to great, the system will start defueling (very similar if it see excess EGT only for a much longer period, until pressure differential is corrected) and will eventually go into limp mode (You were seeing defueling). The new vehicles that operate DEF have no effect on the regen cycle, DEF is a totally separate operation system. You can delete the regen cycle(remove pollution regen chamber) and reprogram, also usually requires removal or by pass of EGR system. The removal does not increase power(but the tuner can be used to increase HP/torque), but does increase fuel mileage, because mileage drops significantly during regen. However any of these modifications will most likely void any remaining factory warranty on engine and transmission.

[grayghost03]

Just a side note, had a buddy who drove a 2008 F250(same system) and he lived 10 miles from our job sight, yep, you guessed it, his would go into regen, never have enough time to complete, restart, going and coming and would get 7 mpg for a week, until he made time to take it out on the highway and run it down the road for 30 or 40 miles to get a complete regen. Ain't technology grand. We run a lot of trucks that the pollution systems "have fallen off of" and have tunes applied. Haven't found the need on the new Chevy "yet" but will if I have any problems with or created by the pollution system.

[Drifty1]

Last summer I replaced all my emission controls on my Dodge to the tune of about $8,500. At that time I asked if something was wrong with the emissions why did I not get a regen required warning on the overhead counsel and the Dodge mechanic said they had so many problems with people coming in every time the warning came on that Dodge reprogrammed the flash so the warning would not show up at all. Now I have no idea if the truck regens at all. I think this is just plain nuts...Next problem I have with this the dpf filter and inter cooler are gone...

[Carl n Susan]

A couple of caveats. One, you are probably better off asking about this on one of the Chevy diesel forums. Lots of knowledgeable folks there. Two, I have a Ford (actually two) which does regens. I know how it works, and I think the Chevy is similar, but I could be wrong.

You are correct in that the regen process burns up the soot collected in the diesel particulate filter (DPF) component of the exhaust system. There are two types of regen: passive and active. Passive regens occur when the exhaust is hot enough (over 550 degrees on a Ford) to automatically incinerate the soot in the DPF. You pretty much have to be towing and working the engine for this to occur. If the DPF starts to fill with soot, and a "passive" regen isn't an option, the computer will initiate an "active" regen. This means dumping raw diesel fuel into the exhaust system. The fuel burns in the exhaust and raises the temperature there enough to incinerate the soot. One criteria is you have to be traveling over a certain speed (35 MPH as I recall). You also need to keep driving until it finishes.

The regen process does not increase the engine RPMs on you, nor does it run the engine fan. All the heat generated is contained in the exhaust, not the engine. Touching the brake does not stop the regen as long as you don't stop. The exhaust pipe does get hot but since you are traveling down the road, there is a cooling effect to prevent burning the surrounding area. The early Ford (6.4L 2008 - 2010) implementation limited boost to 20 PSI when a regen was active. This was noticeable when towing a heavy load up a hill (it always seemed to happen to me at that time). Perhaps the early Chevy implementation is similar. In no case the reduction in power was such that you couldn't do what was needed. The newer Ford (6.7L 2011 - current) make regen transparent. You can't tell when one is happening based on performance.

If the regen is not allowed to complete repeatedly there are consequences. On the Ford you get a message to "drive until complete" and power is restricted. Ultimately it goes into "limp" mode and you get a trip to the dealer to clear it.

The bottom line is these new diesels engines do not make good around town drivers. They need to be on the road and worked to operate best.

Here is a quick reference to get you started on understanding how regens work
http://en.wikipedia.org/wiki/Diesel_particulate_filter

[bethandkevin]

My 2008 has the same DPF(Diesel Particulate Filter) system you have. Or at least it used to. I removed it and installed an Edge Race Evolution Tuner. I'm sure there are others. I had read that tuners that eliminated DPF's or any other emission device were either going to become hard to get, or not available at all. The last straw for me was when it went into regen mode and lasted for eighty miles. If you watch your mileage in regen, it's about half normal driving mileage. My DPF has been stored in the barn for two years without any truck issues. I took it off well after warranty expired and I now have 152,000 miles on Vinnie.

[K0LCB]

I guess that is where my dad got the idea that a truck needed to be taken out on the highway once in awhile to "blow the cobwebs out"!

[CORattler]

My truck's regen process is much like what Carl described. I do not have to drive fast to get a passive regen to complete. It is all about getting the exhaust hot enough to burn off the accumulated soot in the DPF and keeping it that way for the duration of the regen. I keep my RPMs up to keep the exhaust hot and do about 40 MPH until the regen light goes out.

[mlh]

I got rid of the DPF and the EGR. In other words about all of the emission controls. The EGR delete was about $300 and the tuner and straight pipe to get rid of the EGR was about $1200. With my tuner I have at least 30 different tunes. They range from no HP increase to 310 rear wheel increase, EGR DPF on or off. I use the 210 HP tow tune with DPF and EGR off. That tune gives me a little over 600 fly wheel HP and a little over 1100 pound feet of torque. I use it because it is a nice safe tune, The engine and transmission can easily handle the horse power and toque and it leaves all the Ford built in safe guards in place. The main reason I tuned my truck was I had 13% fuel in the oil and Ford couldn't help me. The Chevys don't have this problem, they have a 9th injector that Ford and Dodge don't have. If you have a Ford or Dodge and you have your oil checked you might be surprised at what you find. I was shocked. Where you find a problem is when you don't let the engine go through its complete regen cycle like has been talked about here. I didn't tune for more power but it is nice. People say you don't need that much power but I've never heard anybody say their truck had too much power.
Lynwood

[KathyandDave]

I'm just checking back in. The knowledgable mechanic was puzzled that the DIC didn't indicate a regen. The more recent units do.

[scott-pati]

Removed the regen from my truck when it only had 1500 miles on it. I hit a speed bump going to fast and the whole exhaust system fell off the truck. I looked in my rear mirror as it was sliding down the road and sparks were flying. LOL

[bigskyjimmy]

AHHHH the joys of newer diesel's,Powerfull rigs but you pay a price for it, I think I will just stick with my Old LB7 Duramax with a Banks tuner 0, Zip, Nada, ZERO emmisions Simplicity is a beautiful thing but in your case for sure get a quality tuner(While you can)like Kevin said EFI Live ,Edge,Banks and bypass that B.S.

[richfaa]

On our 08 F-350 Ford. We have a after market guage that monitors all motor parameters including pre turbo EGT. When in regen the EGT temps go up 400/500 degrees. Performance falls off but not all that much under normal driving conditions, you will note it on a long hard pull..MPG will drop 3/4 MPG. If on a long hard pull with the 5th wheel and it goes into regen the cooling fan may come on .Ours did on fancy gap. A normal regen will last 20 mins.

It is easy for me to see a regen as my EGT (exhaust gas temps) go way up and the gauge is right were I can see it.We do get a notification on the computer disply but it only stays on for 10 or so seconds.If you do a reset on the display it will show there.

[steelpony5555]

Ain't it funny how you can't get a real mechanic anymore. If a check engine light is not on or the computer don't tell these guys something then you are nuts, there ain't nothing wrong with your truck???
I thought if you were towing that was enough to keep the truck running clean and for it not to go into regen?? Oh well I'm gonna keep the government parts on for as long as I can but one more problem and I'm gonna get out the big hammer and it's all gonna go. Even my Dodge service mgr and mechanic said I would be better off with out that stuff.....

[richfaa]

On our way to and from Florida we are on the interstates at 62/65 MPH and we will normally get two regens in the 1200 miles trip. They are active regenerations were fuel is sprayed into the filter and ignited which causes the MPG to decrease and the EGT temps to go up. If on a fairly level road when towing I may not be able to feel it going into regen but I can always see the EGT's go up and can see how long the regen last. If we have been at say 10MPG we will drop to 7 while in regen. You can just about set your watch that it will take 20 mins.

[jbcason]

quote:Originally posted by richfaa

On our way to and from Florida we are on the interstates at 62/65 MPH and we will normally get two regens in the 1200 miles trip. They are active regenerations were fuel is sprayed into the filter and ignited which causes the MPG to decrease and the EGT temps to go up. If on a fairly level road when towing I may not be able to feel it going into regen but I can always see the EGT's go up and can see how long the regen last. If we have been at say 10MPG we will drop to 7 while in regen. You can just about set your watch that it will take 20 mins.

Actuall it sprays the fuel in the cylinder on the exhaust stroke. It does cause fuel dilution in the oil but doesn't seem to hurt anything as long as you change the oil regular.

[richfaa]

We change oil every 3K miles as suggested for heavy duty use. We have no problem with dilution.

[mlh]

The first oil change we tested which was our second change we had 13% fuel in the oil. Ford said they couldn't fix it so I did. I took all of the pollution controls off and now we have less than 1/2 % fuel in the oil. About 1% per 1000 miles is normal for these engines for both Commings and Ford. Chevy doesn't have the problem. They inject fuel for the regen in the exhaust pipe while Ford and Cummings inject it in the engine on the exhaust stroke. After you remove all of the pollution controls you have a far different truck. You would haft to try it to believe it.
Lynwood

[1retired06]

Interesting. I have had no issues with my 6.7, and while in Florida for the winter, because I have no choice, do a lot of short trips.