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2016 regen smoke

Question: 
5K views 22 replies 10 participants last post by  Ted White 
#1 · (Edited by Moderator)
had truck since new, has 13000 on it now; noticed smoke during the regen today on a hard accel. never noticed smoke before. question is, while trucks are in regen, is a haze/smoke from the tail pipe during accel a normal condition? called dealer and they said ya it can be. no CEL or dash lights are on.
 
#3 ·
yup,its normal,,saw it from my truck do it on the highway.freaked for a bit,then next time it happened,I'm like,,this has to be normal.:D
 
#4 ·
And when people behind you have to slam on the brakes because they suddenly can't see where they're driving anymore and get SO pissed about it that they follow you to your next stop to chew you out for "how ****ty your truck runs", and how "you're destroying the environment", just try to keep a straight face while attempting to explain to them that our government has determined that they were temporarily engulfed in an opaque cloud of god-knows-what because that makes it run cleaner...
 
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#6 ·
And don't forget that burning this chemical that came from a non recyclable plastic bottled boxed in a carboard box!
 
#7 ·
This makes sense during a regen with the additional fuel added to burn off.
Deleted mine does the samething after mild city driving for a while then getting on a freeway and merging in.
 
#8 ·
When the 9th injector was first added to inject fuel during regens, clouds of white smoke were the symptoms of a faulty injector. If the spray from the injector is uneven, with too many large fuel droplets, white smoke is produced. So, although a lot of folks are saying it is normal, I can't help wondering whether the 9th injectors are ageing and becoming problematic.
 
#11 ·
Mine only does under load, which can be as simple as maintaining speed on the highway when the incline changes a little. That said, it isn't linear based on load, it's more like a light switch. It either smokes a lot or not at all, with a crack of the throttle.
 
#14 ·
If it doesn't smoke, how do you even know it's in regen? Unless you're watching the mpg drop for no good reason. My '15 gives me no indication at all. Only truck (other Chevy's included) I've ever driven that didn't have something pop up in the DIC to say that it's in regen.
 
#16 ·
on the highway mine doesn't smoke. If it is doing a regen during in town driving with lots of stop and go, it will smoke on moderate acceleration after waiting for a red light.
 
#18 ·
As already mentioned, in past years, smoke during regens was an indication that too much fuel, or a badly formed spray of fuel, was being injected during regens, particularly on models with the 9th injector. If my truck was smoking during regens, I would want to check whether the 9th injector was faulty.
 
#20 ·
According to a friend who worked on the original fuel programming team for the 9th injector trucks, the spray pattern from the nozzle is critical to proper burning of the injected fuel. There is a complex interaction between the DOC, the 9th injector, and the DPF, to ensure that oxygen released from the exhaust gasses by the DOC is properly utilized by the injected fuel to increase exhaust gas temperatures. If the 9th injector spray droplets are too large, or there is too much fuel being injected, white smoke will be produced due to incomplete combustion of the fuel. This will be most noticeable during periods of acceleration while a regen is underway, because even more fuel is injected during acceleration. So, if it was my truck smoking during regens, I would be suspicious that the system is not working correctly.
 
#21 ·
Seems like there aught to be something coming up in the DIC if that's the case, it's more than happy to incrementally restrict my top speed for every other little imperfection it's super smart little brain detects until I address it...
 
#22 ·
during the regen the carbon (soot) in the DPF is burned off to an ash. So..... in a properly operating system to me the question is. Is the white "smoke" unburned fuel or just the white ash from the DPF regen process. Under a reasonable highway load I wouldn't expect to see the ash as visible. But stop at a light, not much exhaust flow, ash is still being formed and give it some throttle and what may be coming out is just a pile of ash.
 
#23 · (Edited)
Actually, the carbon (soot) burns off using oxygen released from the exhaust gasses by the DOC (Diesel Oxygen Catalyst). The carbon combines with the oxygen (C + O2 = CO2) to form CO2, which is carbon dioxide, a colorless, odorless gas, which exits the exhaust pipe.

Ash is NOT formed from the burning of the carbon, it is formed in tiny, tiny amounts from the combustion of impurities in the fuel and lubricating oil - that's why trucks with DPFs need low ash oil.

The ash accumulates in the DPF, TRAPPED BY THE FILTER, and eventually clogs it, requiring specialized cleaning.

If I remember the regulations correctly, the EPA requires the DPF to go at least 150,000 miles before needing cleaning.

So, bottom line, the white smoke is NOT ash. It is partially burned fuel from an oxygen starved environment in the exhaust line. Oxygen starvation occurs when accelerating if the 9th injector is sending too much fuel into the exhaust.
 
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