Do 2007+ OM642 Diesels have post combustion fuel injection for the DPF?

-D-

Member
Was just doing some reading on bio-diesel and found this write-up.

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/419605551/m/2721003282/p/1

Summary is that many 2007+ Diesel motors will inject a small amount of fuel after the combustion process just to be vaporized and flushed out to the DPF..

First question I have is do our diesels do this?

Second is, does anyone else think this is odd? Wouldn't the bio diesel showing up in the crank case (sump) suggest a large amount of cylinder blow-by? Also, why don't we see a large amount of dino diesel showing up now if this is the case? We are supposed to believe that dino diesel atomizes substantially better and thus is exhausted more efficiently, but bio-diesel is plenty adequate for combustion?

EDIT: Answer to question #2

Post-injection of fuel into the cylinders is intended to vaporize in the cylinder but not combust, exiting then through the exhaust valves and traveling downstream where the introduction of the unburned fuel to the catalyst creates an exothermic reaction incinerating the collected soot. Inevitably the heavier fractions of fuel will not vaporize during post-injection and in liquid form can adhere to the cylinder walls. Through the slapping motion of the pistons and oil rings, the unburned fuel from post-injection can make its way through the tight, hot quarters between the piston, rings and cylinder walls. The fuel accumulates in the crankcase and dilutes the oil, which is a major concern regarding engine wear and longevity.

"Using post-injection you will generally see elevated levels of fuel dilution regardless of what fuel you're using," Sappok says. Because biodiesel has a higher distillation temperature and boiling point, when it's present in the post-injected fuel it tends to dilute the oil on a level disproportionate to its blend ratio in the fuel. Fang says this is just now becoming understood.


from here:

http://www.biodieselmagazine.com/articles/2290/understanding-the-post-injection-problem/
 
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piper1

Resident Oil Nerd.
Was just doing some reading on bio-diesel and found this write-up.

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/419605551/m/2721003282/p/1

Summary is that many 2007+ Diesel motors will inject a small amount of fuel after the combustion process just to be vaporized and flushed out to the DPF..

First question I have is do our diesels do this?
Yes....any diesel that has a DPF that requires an ECM triggered re-gen will do this. I know of no 2007+ diesel that does not. Some do it a lot less (Volvo HD comes to mind) but all will do it if they need to. A 2007-2010 NAFTA diesel Sprinter does it every 700 miles or so.

Second is, does anyone else think this is odd? Wouldn't the bio diesel showing up in the crank case (sump) suggest a large amount of cylinder blow-by? Also, why don't we see a large amount of dino diesel showing up now if this is the case? We are supposed to believe that dino diesel atomizes substantially better and thus is exhausted more efficiently, but bio-diesel is plenty adequate for combustion?
Is it odd...no. It's the new normal. It also does not suggest a lot of blowby. The fuel is being introduced into the cylinder in an environment where it will not burn, unlike a regular power injection event. Some new diesels do this DPF injection with a separate injector outside the combustion chamber to avoid this.

Does Bio-Diesel not atomize as good as regular diesel....in a word...yes. It does atomize well enough in a regular combustion event in a quite very nice way. Bio diesel is an awesome fuel.....as far as it being a fuel that works equally well in a post injection event....no. Keep in mind, a 5-15% bio blend is not an issue.....50% or higher and you just have to be a bit more diligent in keeping an eye on things. In non DPF diesels I have run pure bio...and had no issues. The Sprinter gets 10 % max....mainly because my mileage goes down too much (a Sprinter oddity).

EDIT: Answer to question #2

Post-injection of fuel into the cylinders is intended to vaporize in the cylinder but not combust, exiting then through the exhaust valves and traveling downstream where the introduction of the unburned fuel to the catalyst creates an exothermic reaction incinerating the collected soot. Inevitably the heavier fractions of fuel will not vaporize during post-injection and in liquid form can adhere to the cylinder walls. Through the slapping motion of the pistons and oil rings, the unburned fuel from post-injection can make its way through the tight, hot quarters between the piston, rings and cylinder walls. The fuel accumulates in the crankcase and dilutes the oil, which is a major concern regarding engine wear and longevity.

"Using post-injection you will generally see elevated levels of fuel dilution regardless of what fuel you're using," Sappok says. Because biodiesel has a higher distillation temperature and boiling point, when it's present in the post-injected fuel it tends to dilute the oil on a level disproportionate to its blend ratio in the fuel. Fang says this is just now becoming understood.


from here:

http://www.biodieselmagazine.com/articles/2290/understanding-the-post-injection-problem/
 

flman

Well-known member
It occurred to me while reading one of CustomSpoolings posts he asked the question, "Have you noticed the level of your oil increasing in city driving?"

Then I put 2 and 2 together, why is our NCV3 vans are able to check the oil from the dashboard? To prevent catastrophic failure of the engines. I have read if you add a little bit of extra oil you will get a high oil level light. It is actually a feature that is built in for the ECM to monitor oil level, since there was already sensors it was easily added to the info center to allow a quick check of your oil level. Obviously the engineers at MB knew that the engine could be washed out by diesel fuel due to DPF regens. Also, I have heard other NCV3 owners say they never need to top off between oil changes.
 
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icarus

Active member
I never have to add oil between changes on any of my other vehicles,, those without DPFs.

Icarus.

PS. I see a rehash of the same conversations about DPFs that are on the recently closed thread.
 

flman

Well-known member
I never have to add oil between changes on any of my other vehicles,, those without DPFs.

Icarus.

PS. I see a rehash of the same conversations about DPFs that are on the recently closed thread.
This is a thread about oil dilution in DPF vehicles. Would it be better if some one that drove in heavy traffic all day blew an engine, or had to have it towed due to a high oil level light? :thinking:

What is your problem? :crazy:
 

icarus

Active member
I don't have a problem, I was merely noting that I never had to add oil to any other vehicle between changes.

Icarus
 

CustomSpooling

Custom ECU tuning.
Google these words - dpf oil level rising

You will find tonnes of topics about it on all different kinds of vehicles including Mercedes.
 

flman

Well-known member
Google these words - dpf oil level rising

You will find tonnes of topics about it on all different kinds of vehicles including Mercedes.
I did the search, over 10 pages were relevant to the search terms. I guess it is pretty common, I will watch my oil level much closer now.
 

CustomSpooling

Custom ECU tuning.
I did the search, over 10 pages were relevant to the search terms. I guess it is pretty common, I will watch my oil level much closer now.
It will happen more with city drivers. If you are always on a motorway then regenerations (passive regen) can occur by reaching the higher temperatures to burn off ash without the need for post fuel injection cycles.

Read up or Passive regen and Active regen. City drivers will experience Active regenerations.
 

jdcaples

Not Suitable w/220v Gen

jackbombay

Active member
I think UOA means used oil analysis.
Yep.

And the 3 UOAs in that PDF all have minimal fuel in the oil, nothing to be concerned about.

If someone has some UOAs from a van that spends all or most of its time doing city driving I would be interested to see the fuel percentage in the UOAs.
 

Ovalmaster

New member
I am ready for a my first oil change, and just still when I just checked the level it was still spot on, and have never added any. I do 95% city driving, and have noticed it regen about every 700miles.
 

jackbombay

Active member
I am ready for a my first oil change, and just still when I just checked the level it was still spot on, and have never added any. I do 95% city driving, and have noticed it regen about every 700miles.
Are you planning on having the used oil analyzed?
 

cedarsanctum

re: Member
I have an 08 that gets used mostly on the highway, no stop and go once i'm out of town (and that's usually only 1-2 lights). That's 20,000 miles of very little idling or very slow travel.
Just before both services became due, the low oil warning came on. Last time was in California on a trip, had to find the oil and add a quart to make it go away. I believe it still showed low on the dipstick, but it was going for a change when we got home, so i let it go.
What does that say about this discussion. There's no fuel getting washed down into my engine? An engine that gets mostly highway miles will be better for the DPF than an around town rig? I would be curious to see what oil consumption differences are between city and highway miles.
Jef
 

jackbombay

Active member
No I'm not. sorry:frown:
No worries, I'm sure your van is fine. I haven't seen any UOAs to support the claims of "the sky is falling/my oil is diluted" crowd anyway so until someone posts up some UOA results showing notable fuel content in the oil there is no reason to believe what they say.
 

icarus

Active member
You must have some miracle vehicles to say never?
No miracle vehicle, I just treat them well, in general.

The last vehicle I had to add oil to was my 82 VW rabbit pick up. Current vehicles include a 07 Prius, with 70k in it, and a 99 Subaru outback. I change oil between 3-5k and expect to get 200 k without major service.

If one thinks one has a problem with oil contamination, a used oil analysis will give a pretty good indication of engine health, and possible contamination issues.


Interesting to note, reading the UOA that Jd linked, shows fuel contamination 1/4 the recommended percentage, .5 as opposed to 2.0%. So much for the hysteria about oil dilution.
https://sprinter-source.com/forums/attachment.php?attachmentid=31671&d=1301492212

Icarus
 
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