6.7L Cummins Forum

Folks,

Was doing some homework on Bio diesel as it relates to Cummins 6.7L engine and DPF. Found some great info I thought I would pass on.

- Understanding post injection (DPF regen process):

Understanding the Post-Injection Problem - Biodiesel Magazine

- What Is A DPF And How Does It Work? :

Turbo Diesel

What's found so far about bio diesel in modern diesel engine with particulate filters. Since dino fuel doesn't burn cleanly so soot is produced. This soot gets in the oil and in the exhaust and in particularly in the catalytic converter. Diesel engine manufacturers have decided to help the catalytic converter out by placing a soot collection screen in the exhaust path prior to the cat. Then as the differential pressure changes with screen plugging a "regeneration cycle" initiates.

This injects fuel into the compression chamber during the exhaust stroke the dino diesel combust burning out the exhaust stream and burning the soot off the catalytic converters protection screen.

When you put bio diesel into the mix since it is more viscous and doesn't combust as readily it tends to coat the piston chamber during this regeneration cycle and then gets squeegeed by the multiple piston rings off the cylinder walls, right into the crank case oil. This is very bad. This dilutes the motor oil significantly according to Volkswagen and therefore requires the oil to be changed out more regularly than they would like or intend with anything more than B5...(45% dilution in 10,000 miles).

Now I understand why Cummins has such a low bio mix rating for the 6.7. Nothing to do with the water content of bio (though part of it), but how the post injection process works and how it interacts with the engine oil.

Wonder how this all works out when post injection is removed and urea (which uses its own injection process) is used with relation to bio diesel.

So if you use a B5 mix, oil change should be about 5K interval, if you use B10, its shorten to about 3K interval. B100 is out of the question on the 6.7 with post injection process the best that I can tell so far.

Bypass oil filtration with bio diesel does become extremely important !

Hope this helps others.

Cheers.

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More information ...

Folks experimenting with Bio mixes and DPF's have found that B100 will NOT allow the DPF to work correctly. Highest mix found so far has been 33% bio, 67% Diesel, DPF works correctly. They also noted at 33%, the oil gets contaminated very quickly. No bypass filtration used.

Cheers.

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Thanks for that great info!

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2008 Dodge 2500HD 6.7L 4X4 Laramie
Edge insight, Amp tailgate step, 4" Boss Bars, rear air bags with compressor, spray in bed liner