it is somewhere in print, but i can't find it at the moment...

it more or less is due to the 3rd injection event the oil turning black... the cam timing is also retarded 7° i believe... an engine with an egr system will get black oil real quick... cummins doesn't use an egr system, but they use "In-cylinder combustion and diesel oxidation catalyst solution requires no exhaust gas circulation components". the 3rd shot is there to keep the cat hot for it to work properly. with more fuel being introduced into the cylinder, there is more soot/exhaust that doesn't get scavanged when the valve overlap happens.. if there is more that isn't scavanged out, when compression comes around, there is more that can bypass the rings and enter the engine crankcase where the oil grabs it... the 3rd shot will not burn as completely either when compared to the pilot and main events... the pilot shot ignites easially, and the main event ignites nicely with the pilot already burning. now when the 3rd event happens, the piston is already down the bore somewhat and you have less pressure there, less oxygen to combust the fuel, but you have the heat to char the fuel...

 

I'll guess that one of the major emissions problems that Cummins had to address in order to be 50 state legal is nitrogen compounds, which is usually a problem with high combustion temperatures. The 555 HO engines ran kind of hot, they also ended up usually running clean too, but they didn't meet CARB requirements. If the newer engines have lower nitrogen compounds they probably also have lower combustion termperatures, and consequently more soot.

 

Interesting thread...

First, I'd speculate that running an engine "hot" doesn't make the cat run better. The cat functions as a result of mixing unburned hydrocarbons and oxygen after the internal combustion event. The end result is really what we might think of as a controlled burn and it's cleaner because no compression is involved (at the cat). If the initial combustion event is too complete, then there isn't enough unburned hydrocarbon to allow the cat to work.

That being said, we were really commenting on the oil appearing to get dirty very quickly on our 600's. If I were to guess, then I'd say that our engines are pretty normal up to the last tiny sqirt. The first comes just before TDC, the second just a bit after that, and the last well after the piston is on the downward stroke.

Since the function of the last injection event is to leave a bit of unburned fuel and the cylinder is decompressing quickly at the time, it would stand to reason that we might get a pretty sooty "burn" at nearly BDC with a microscopic coat of soot having been deposited on the cylinder walls.

This is, perhaps, not a bad thing at all. First, it makes good fuel for the cat. Second, the pure carbon nature of the soot probably has some lubricity that's added to the thin coat of oil protecting the cylinder walls. What we notice is that our oil is doing a great job in capturing that soot.

Which brings to mind something else... Since our soot levels aren't excessive even after a 15k run, then it's somehow being taken care of while our engines are running. I wonder if this isn't the cause of the increased complaints about certain odors associated more with the 600's than past models?

In any case I'd be willing to bet that should that third event have been routed directly to the cat instead of into our engines, that we'd run as clean as past engines and that our cats would be just as happy.

Two things prevent direct injection into the cat. First is the added expense and complexity of such. Second is the fact that some of us would "tinker" with the system and disable it. Thus, we have black oil and a motor that sounds a bit funny.

As I said, this is just my theory. I'd be willing to put money on it, though.

 

When I change mine and start the truck.. It is so black it looks as if it has not been changed...

 

Nord, are you willing to put money behind your statement that soot on the cylinder walls acts as a lubricant?

 

I think you are not seeing the 3rd event because it doesn't happen all the time. If you are testing while the truck is idling, there is probably only 2 events.

I think there is also some confusion in this thread about running hot. Heat to the catalyst doesn't increase its performance (ability to remove HC's and NOx), but heat is how the cat stays clean (not plugged up). The coolant temps on the 610's are about 10 degrees hotter than the 555's but that certainly would cause the oil to turn black.

Is it possible that if there actually is a little unburned fuel in the cylinder during the exhaust stroke that it is still there when the compression stroke begins and while the pressure is building the extra fuel is partially "cleaning" the cylinder wall and a tiny bit of this fluid that contains byproducts of combustion is "blown by" the rings?

 

Soot is definately not a lubricant. In studying engine wear one lab figured out that they needed to duplicate and standardize the properties of used oil for testing as it produced more wear than fresh oil. One suggestion was to add abrasives to new oil.

 

That's what caught *MY* eye. Soot is ABRASIVE. That's why the new CI-4+ formulation is so heavy on soot dispersants. It's formulated to work better in the high-soot environment caused by cooled EGR and other emissions equipment.

jlh

 

I would hypothesize that the extra dispersants, along with the oil detergents, are what is turning black so quickly. There was a thread on this site early last year or the year before that had a link to engine oil properties and "additive packages", and one of the things the article pointed out is that the detergents in motor oil (both diesel and gasser motor oils) turn black due to oxidation in the cylinder. If extra detergents OR extra soot dispersants are existant in the new motor oils recommended, then I would suspect that is what is turning the oil black so quickly. Just a thought.

 

Soot is abrasive. Anything that gets suspended in our oil probably shouldn't be there. That said, I'm hoping these newer oils are doing a darn good job because it looks like alot of soot.

Now back to the situation. If, in fact the 555's have oil that is remaining cleaner... IF... and the engines are 99% the same with a slightly different cam and ecm. Then how about one of our extremely talented "tuner" companies build us a box/programmer that takes care of this "problem" of dirty oil. I still don't know if the earlier gen ISB's ran cleaner oil or not. But I'd have to think someone out there can do something to correct this. I cannot fathom how this dirty oil can be as good for our engines as clean/clearer oil.

Tony

 

Well guys, I guess I'll just put the soot issue aside as a possible lubricant. Carbon is a pretty difficult thing to pin down as it has so many different properties depending on what state it's in. I will say that whatever soot that's deposited within the engine seems not to be a cause for concern. Thus, the effect it has must be very minor.

As to the rest, I still stand by my opinion. If our oil is entraining the amount of soot we seem to think, then why does it stay at such low levels over time? My guess is that the soot is being given up. Our crankcase perfume is coming from somewhere. Do you suppose there's a connection?

The cat... Heat makes it start the process of doing what cats do. I'll agree to that. On the other hand, complete (and hot) combustion makes for the formation of sulphur and nitrogen oxides. Thus the EGR in gassers and some diesels as it actually limits combustion temps even though the engine runs hotter.

Our third injection event does about the same thing and the cat takes care of the results. Probably not a bad thing I guess.

Anyway, the thread is very enjoyable. Perhaps we'll all learn something.

 

To me the bottom line you guys are all missing is that soot in engine oil typically doesn't become an abrasion problem until it exceeds 3%, which is typically the upper limit on oil analysis reports. Even though the oil in the 600's LOOKS black, most reports are showing very very low soot - like less than half a percent. Black oil does not = bad oil, it's a diesel, for the most part they ALL turn the oil black!

Trik396 and other doubters - you guys are making me . Will it take someone with 7500 miles on the oil posting a pic of the dipstick? Then you guys will probably say it was fresh oil and still question what we're telling you....lol I love the skeptics. For the record, it is FACT that the 555's keep the oil remarkably clean and clear, assuming they are stock and running correctly. For those that have been around here for a few years, you'll remember when the first 04.5's came out and the guys who previously owned 03-04's were freaking out about the black oil...

 

Lightman, I don't doubt you at all. Actually the word would be ENVY.... . I'll be doing an oil analysis shortly to ease my worried mind. Like I said earlier, it'd be cool if some wizard can burn a chip and make my dirty oil clean once again....

 

My oil too turns black in what seems to be about 10 minutes after changing it. Ive given up on caring about it.
Scott

 

I'll take that bet.

I want to see the dipstick (literally) when you do an oil change at 7500 miles.

More than one truck too.