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I was rooting around on the web today and found some more info from Cummin's buried in a document that they presented to a group of their investors. The info is pasted below, I added the under lining and such to point out key info.

"Cummins does so with cooled exhaust-gas recirculation (C-EGR).
The system consists of a Holset variable geometry turbocharger (VGT), an EGR valve to vary the amount of exhaust that is fed back into the engine, a cooler that transfers the exhaust heat to the cooling system, and a mixer that is mounted between the charge air cooler and the engine's charge inlet port.
The critical part of the Cummins EGR solution is the VGT, which is in the system to maintain exhaust pressure and hence push the recirculated exhaust into the high pressure inlet stream. Obviously, there is some pretty sophisticated control in the engine electronics that manages the EGR flow, fuel and boost.
The reason for the exhaust gas in the inlet stream is that the burnt fuel products and the low oxygen level mean that the incoming stream is basically inert. As such, it allows for the peak combustion temperature inside the combustion chambers to be lowered, reducing the formation of nitrogen oxides, which are the target of this emissions regulation.
The downside is that the engine is seeing a steady stream of combustion products that includes acids and soot, not a healthy diet, you could suppose.
And therein lies some of the concern about C-EGR technology: What will be the reliability and durability?
To date, reliability has been good and Cummins can point to the proof of its Holset VGT, which is working nicely on more than 50,000 Iveco engines in Europe. Concerns about maintenance intervals and oil condition have been addressed by the new category CJ-4 oils.

The use of lower-sulfur ULSD fuel in the Cummins is critical to reduce fuel-caused sulfuric acid corrosion expected from cooled EGR for NOx control.

Maybe I'm the only one who missed it, but I never made the connection before that the VGT turbo was a key component of the EGR system, but seeing this info now it makes perfect sense.

This would also appear to explain why sometimes the EB doesn't seem to work as strongly or sound as loud, depending on whether or not the EGR valve is open or not, which would remove some of the pressure from the EB.

Also makes you wonder if the real reason we've been told to use the EB all of the time is to keep soot from forming?

If you think about it, using the EB increases the back pressure which would in turn force more exhaust gases through the EGR system than running without the EB.

Also makes you wonder if running the EB all of the time could contribute to making your oil level rise faster than not running it?

The regen cycle injects raw fuel on the exhaust stroke for the CAT/NoX process. If the EB is on, its going to increase the back pressure in the cylinders (which could force some of this fuel past the rings into the crankcase?) as well as forcing some of that fuel through the EGR system.

We need some of the hard core engine and systems experts to weigh in on this with their 2 cents.

Also worth noting the comment about sulphuric acid corrosion. For all of you that have deleted your DPF's, you might want to make sure you are still burning ULSD until you also get the EGR removed.

My head huts now, time for some:popcorn: and some:beer
 

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Delete egr and cooler and problem solved. :thumbsup
 

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just delete all that stuff..it takes away 20-40% of the engine efficiency
 

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Thanks for the info. If gets more interesting with these 6.7's by the day.

Delete egr and cooler and problem solved. :thumbsup
What do you mean by "cooler?" Thanks for helping the ignorant.
 

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The other diesel builders seem to be going to urea injection, which doesn't need as much EGR as I understand it. I'm not sure Cummins is on the right track.

I guess the aftermarket is going to have to reverse engineer the system. I was thinking today of some kind of restrictor that reduce the EGR total volume but not entirely blank it off. Sort of have the motor eat 50% less soot. All the engine controls would still think everything is working, all the sensors and valves would still be operational but less total EGR volume.
 

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The other diesel builders seem to be going to urea injection,
On trucks or cars? I've read about a Benz that is using urea and I think they stated that one gallon would go for about 2400 miles and would have to be refilled by the dealer.

I have also been thinking about an EGR restrictor but I'm still gathering information on how the system works in stock form.
 
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