Why do DI motors carbon up?

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Originally Posted By: MoultrieCreek
I see this topic pop up in automotive forums all the time and wonder the same thing myself. Diesel motors never spray fuel on their intake valves, and I've never heard of any unusual or excessive service to clean carbon deposits from them... in the meantime I think these discussions have promoted the sale of lots of "catch cans" and a new recommended service of pulling the manifold to clean valves. I do suspect there is something here I don't understand because of the fact Toyota found it wise to keep the dual MP and DI systems on a few models. I keep reading these posts now that I own a DI Chevy truck with 37K miles on it just to see if there is a problem on the horizon - but I'm pretty confident so far they have engineered a better engine than the last generation.


I never thought about this until you pointed it out. I have had the cylinder heads off of several diesel engines, from 6v53 Detroits to 903 Cummins, 7.3 PowerStrokes, 6.5 GM Diesels turbo and non turbo. I have never witnessed any carbon build up on the back side of the intake valves that I would consider excessive.
This is very interesting topic to me, I have a 2015 F150 with the 3.5 Ecoboost. I'm curious to see how it performs over the long haul. So far it's amazing to me, the power it's very diesel like in it's power delivery to me.
 
Originally Posted By: Quattro Pete
Quote:
Can you confirm or deny the 2.0 TFSI now has both too?

I've read somewhere that it does in some markets, but I don't think North America is one of these markets.

As far as the 3.0 engine, check out this list of vehicles using the same part number which is a low pressure injector valve...

http://www.realoem.me/search/tvn/06E906031


Sigh. I emailed Audi, and this is what they said:

"
We can confirm that the 3.0 supercharged engine is direct injection only and the 4.0 TFSI is direct injection only in North America. While it was dual injection in Europe, only direct injection was made available to us as other markets have different emission and safety regulations than in Canada.

We hope this addresses your inquiries, and should you have any further questions or comments please do not hesitate to contact us through our Customer Care Center at (800) 822-2834. We are open Monday through Friday 8:00am to 8:00pm, Eastern Standard Time.

Sincerely,
"

My query was for the D4 A8. Does anyone know for sure?

My reply back:

"I just spoke to a mechanic at xxx Audi in xxx (master mechanic). He had indicated the 3.0T engine in the D4 A8 does indeed have both port fuel injection and dual injection.

In particular, this part number: http://www.realoem.me/search/tvn/06E906031 is the low pressure (port fuel injection valve) for the 3.0 engine, and there is one per cylinder as per http://www.realoem.me/Audi/CA/A8/2017/771/R/1/133/133024#26

Can you please confirm?
 
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If I drive like the old duffer I've become, I can get 37 mpg on e 10 reglar with the Camry LE. I think that is great MPG. Better than a '66 bug
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Originally Posted By: rodinator1234
Originally Posted By: MoultrieCreek
I see this topic pop up in automotive forums all the time and wonder the same thing myself. Diesel motors never spray fuel on their intake valves, and I've never heard of any unusual or excessive service to clean carbon deposits from them... in the meantime I think these discussions have promoted the sale of lots of "catch cans" and a new recommended service of pulling the manifold to clean valves. I do suspect there is something here I don't understand because of the fact Toyota found it wise to keep the dual MP and DI systems on a few models. I keep reading these posts now that I own a DI Chevy truck with 37K miles on it just to see if there is a problem on the horizon - but I'm pretty confident so far they have engineered a better engine than the last generation.


I never thought about this until you pointed it out. I have had the cylinder heads off of several diesel engines, from 6v53 Detroits to 903 Cummins, 7.3 PowerStrokes, 6.5 GM Diesels turbo and non turbo. I have never witnessed any carbon build up on the back side of the intake valves that I would consider excessive.
This is very interesting topic to me, I have a 2015 F150 with the 3.5 Ecoboost. I'm curious to see how it performs over the long haul. So far it's amazing to me, the power it's very diesel like in it's power delivery to me.


The BMW M57 (335d/X5 diesel US 2009-2012?) and many VW diesels built up large amounts of carbon within the intake tract. EGR can be a PITA.
 
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