Carbon build-up in DI engines

Mitco39

Diesels have been direct injected right from the start. Why do they not see this sort of thing happening? Its the same systems (EGR, PCV) on both engines.

Water injection could be used to keep them clean no?

The Bimmer world uses Walnut blasting.

REVIEW: Cleaning of intake valves with BMW walnut shell blasting tool

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2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
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FlyByGTI

I think it might have something to do with the way you are supposed to drive a diesel. I believe you are supposed to be driving them at high RPMs from the very beginning of their life, which is going to keep the carbon build up to a minimum is done properly

I may be misinformed on that though

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Mitco39

You got it backwards. Modern pickup diesels like to run anywhere from 1600rpm to 2200rpm. Most red line or have rev limters around 3500rpm.

Thinking about this after I posted it thought it could have something to do with the higher boost keeping the gunk from sticking. Mind you at cruise a diesel only sits around 2-5PSI.

__________________
2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
My Build --> http://www.the370z.com/members-370z-...39s-build.html

FlyByGTI

I guess that would make sense. I didn't really know about the truck aspect of it, but was thinking about it from the point of view of smaller diesels (ie. Golf TDI).

Never owned a diesel so I don't really have a huge abundance of knowledge with them.

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Mitco39

Im just curious as to what causes this to be an issue here but yet you can have a diesel with 500K miles and the valves will look ok (not good, but not coated like that picture by any means). Maybe there ports are designed in such a way to speed up the air entering the cylinder so that the air moves much faster around the valve? I know for a fact that the EGR systems on a diesel are way way more messy than that of a gas engine. All that soot goes into the intake tract. If you could find the difference between the two I think you would be well on your way to a solution. For all we know it could even just be a special coating on the valves.

__________________
2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
My Build --> http://www.the370z.com/members-370z-...39s-build.html

FlyByGTI

Looking around it seems like there are a few things with the Diesel direct injection that are interesting. Apparently the biggest issue facing those engines is idling. The recommendation (and this may explain why cummins drivers seem like d-bags all the time), is that to combat the build up in diesel engines you should floor it 10-15 times a drive. Apparently the way that the EGR is setup, it closes during full fuelling which means that flooring it should blast away all the crud and gunk. It doesn't seem like the Gas Direct Injection has that same setup on them. It looks like the smaller displacement turbo cars should have an easier time avoiding carbon buildup because they are more likely under heavy load for longer periods of time.

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Mitco39

Thats not entirely true. I have seen the inside of diesel engines on farm trucks driven by old farmers with nothing out of the ordinary in terms of build up. I mean you always will have some but nothing to affect performance a noticeable amount or anything like that. Surely nothing like that picture. I suggest deleting the external EGR where ever possible, its just not a good setup. Most new cars just have a internal EGR by changing the cam degrees with respect to each other.

I bet if there was a way to turn this off on the Z you would see both fuel mileage and power gains from it. The Z does not have external EGR system on it, so it only leads me to believe it is controlled by the VVEL.

__________________
2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
My Build --> http://www.the370z.com/members-370z-...39s-build.html