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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW Passat Family (NMS and B7) TDIs (2012+)

VW Passat Family (NMS and B7) TDIs (2012+) Discussion area for the 2012+ Passat TDI (North American and rest of world versions versions). The North American model was previously codenamed NMS (New Midsize Sedan) and the version the rest of the world gets is sometimes referred to as B7.

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Old July 2nd, 2017, 07:03   #16
Mark_J
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"The late injection for the DPF is not burned in the cylinder". I'm confused, isn't the DPF injected quite a ways down stream of the engine in the exhaust pipe before the catalyst, so how would it get into the cylinder? Are you talking about the piston cylinder or something else?
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Old July 2nd, 2017, 07:44   #17
tdiatlast
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Quote:
Originally Posted by rustycat View Post
Yup, our 13 was rock steady on the oil level as well, guess we'll see if the EA288 behaves differently. Again, I couldn't find anything really pointing to an oil dillution characteristic associated with the EA288 while Googling.
Question: If the engine is using (burning) oil at the exact rate of the amount of diluted fuel returned to the sump, wouldn't the oil level stay the same?

Discuss...

(only a UOA would determine this...)
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Old July 2nd, 2017, 07:44   #18
jason_
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No, during a regen raw fuel, for a microsecond or so, is shot near the end of the cycle, before the valve laps shut, and turbo boost is increased a fuzz to promote high filter Temps to reduce soot to ash.

I believe there's 5 or 6 injection periods per stroke?

One to reduce traditional piston clatter, one for the actual power pushing of the piston, one for regens, and others programmed for who know what else?

14,000# of fuel pressure and fast cycle injectors makes for a lot of programming fun...

But there always is the possibility of cylinder wash and fuel getting past the rings. Engine to engine comparisons sometimes people get an outstanding cast of a block and piston ring wear , and very little fuel gets into the oil.

I had a small block Gm that kept turning into and oil burner. Walls would disappear and the rings looked brand now. Bored and sleeved it, and still going strong. Just pulled a 15ton loaded trailer with it, 380,000 miles on those sleeves...

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Old July 2nd, 2017, 08:07   #19
turbobrick240
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Originally Posted by jason_ View Post

14,000# of fuel pressure and fast cycle injectors makes for a lot of programming fun...
Try doubling that. I would prefer a dedicated injector downstream of the turbo to post injection into the cylinders. Though I also never had any dilution issues.
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Old July 2nd, 2017, 08:50   #20
jason_
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Vcds on the 09 never went past 12000. Maybe it's changed on later models?

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Old July 2nd, 2017, 14:13   #21
tadawson
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Quote:
Originally Posted by Mark_J View Post
"The late injection for the DPF is not burned in the cylinder". I'm confused, isn't the DPF injected quite a ways down stream of the engine in the exhaust pipe before the catalyst, so how would it get into the cylinder? Are you talking about the piston cylinder or something else?
Some diesels use downstream injectors, others (the TDI and Cummins I know for certain) use late injection on the main injectors during exhaust instead . . .
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Old July 2nd, 2017, 21:04   #22
Mark_J
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Got it, I thought they were talking about the DEF injection, not injecting the diesel.
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Old July 3rd, 2017, 20:13   #23
Locoelectrician
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Someone explain this to me please. The hierarchy is, egt, cat, and then dpf, in the exhaust stream. How can my egt and dpf temps be at 1200, while the cat is at 800 during a regen? I’m struggling to understand how the two ends of the system can be at 1200 while the middle is at 800.
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Old July 3rd, 2017, 20:27   #24
turbobrick240
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The exhaust gasses cool as they leave the manifold. When they reach the dpf, the post injection fuel vapors (active regen), and trapped soot (all regens) combust and raise the exhaust temps again.
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Old July 3rd, 2017, 20:30   #25
Locoelectrician
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The exhaust gasses cool as they leave the manifold. When they reach the dpf, the post injection fuel vapors (active regen), and trapped soot (all regens) combust and raise the exhaust temps again.
But isnít post manifold pre turbo, aka egt? How does it cool post turbo (cat)and then reheat in the dpf?
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Old July 3rd, 2017, 21:03   #26
turbobrick240
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But isn’t post manifold pre turbo, aka egt? How does it cool post turbo (cat)and then reheat in the dpf?
EGTstands for exhaust gas temperature. There are three egt sensors at different locations in the exhaust path. The manifold and turbo are integrated into one unit on these cars. It is reheated in the dpf due to the regen fuel and soot combusting there.
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Old July 4th, 2017, 05:45   #27
Locoelectrician
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I understand that, and am monitoring all 3. Just doesn’t make sense how the first and last can be hotter than the second. EGT is pre turbo, CAT is post turbo, pre cat, and DPF is obviously the DPF which is last in line. If fuel were sprayed directly into the DPF it would make more sense. Anyways, not the end of the world, was just trying to better understand.
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Old July 4th, 2017, 06:06   #28
turbobrick240
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It makes perfect sense- you just aren't getting it. Why does a woodstove get hot? Because of the burning fuel inside.
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Old July 4th, 2017, 07:08   #29
Locoelectrician
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I get that. But if it’s burning before the turbo, and burning in the dpf, then it has to be burning at the cat. My best guess is it has to do with volume and back pressure, but that’s just a guess.
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Old July 4th, 2017, 07:25   #30
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It's not burning before the turbo (outside the cylinders). It's burning in the dpf. Along with the trapped soot (carbon).
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