Excess blowby

[Marajin]

Looks to me like the piston/cylinder didn't get cooked, and in the rest of the piston, the spray-pattern looks well within spec, but ... You can see that in this case, it certainly suffered heat damage on one side, and the spray-pattern is too high in the one area. It looks too high like Vin described, and is riding on the top edge a bit too much. You can tell that it was not burning the fuel well either, like it had lower than normal compression. I think that everyone is also overlooking the fact that the crack is on the opposite side of the piston from the oil cooling nozzle. If the piston has soot problems in its rings, or a broken oil ring, or soot deposits inside its cooling ring, ... guess what,... it will not be cooled evenly any more,..and can overheat on the one side( typically opposite of the nozzle). This can also contribute to such a failure, and it stands to reason why almost always, it happens on the exhaust side of the engine. -- Personally, I think the cooling nozzles should have been on the exhaust side of the pistons, not the intake for this same reason, but I am not the one who designed the engine now am I.

With an uneven pattern like that, low compression from worn out rings, and possible oil flow problems,... It is likely the soot-producing EGR itself that was holding temps down and it together. -- Remove said soot-producing mandate,.. and guess what. -- It quickly becomes the straw that broke the camels back.

The higher temps of clean combustion that produces no more soot certainly did not help the situation, but it looks like it rather aggravated it instead. -- This is my personal observation on it any ways.

Just like you stated In2trucks,... The tuning alone did not likely cause it,.. but it certainly did not help it in any way, and looking at how an injector that is not in good health can do this,... I would think that a solid conclusion can be drawn/learned form this for everyone...

Considering that when an engine ages and the compression falls off significantly,... The older an engine is,.. and the more worn out it is,... and the more uneven the injector spray pattern is,... the higher the risk you take when removing the "Mandate" on one. Even if it has been done right, and the engine was held well within spec. That risk though, can be amplified when moving the injection mapping up for better fuel efficiency though too... and guess what ,.. the higher you go,.. I would think the more the risk you take on an engine with some spray-pattern and compression issues, and/or one with less than optimal oil cooling of the pistons due to wear in the head reducing the pressure available at the piston cooling nozzles. -- Add this all up, and it can be a recipe for a failure for sure.

This also gives more merit to increasing the oil pressure in these engines by 5+ PSI like everyone was talking about. Perhaps better cooling of the piston and a slightly higher oil pressure could have helped too? -- Just some thoughts. It seems that almost always, the crack, or hole, is on the opposite side of the piston of where the oil is being sprayed into it is all.

It looks to me like that the more soot-packed age someones engine has on it, the higher the risk. -- Programming can help reduce this scenario on an engine that has these types of problems, but at a cost. That cost would be a lower overall injection map offset to keep the pattern deeper into the cup, but it would mean less fuel efficiency. As well,.. there is no predicting how well a piston is being cooled, except to verify that the oil pressure is good for the engine, and that there is not too much wear in the upper end of the motor, as to not starve the lower half.

I would be curious to see how much deposits/coating your pistons have inside them underneath the lower cooling ring like in the photo I have shown below.


I spent a couple hours talking with a few others on this very thing today as well, after seeing the photo.

A general conclusion has been drawn that it is possible to get at least Most of the efficiency back with less risk to an older engine with uneven injector spray-patterns by sharpening the injection curve for the engine in the low-to-mid torque regions only, instead of a blanket offset for better fuel efficiency and cleaner oil. When done this way, at high fueling and torque,.. the pattern is much lower in the cradle and safer for an engine with uneven patterns, -- but under lighter torque (cruising), it can ride higher for better fuel efficiency because there is less overall heat.

The drawback to programming one this way though,.. is that the more power you use at the upper end of the torque band,... the less fuel efficient it would become. -- The result would be an engine that was really nice and fuel efficient with high gains at low-to-mid torque,... when driven lightly,... but under heavy (or full) throttle, all of that going out the window so to speak, as a protection to the engine, amplifying the already known issue of more boost and power = less efficiency greatly.

It could be done, ... so the next question is how does one determine what engines would benefit from this? -- I mean,.. how would a person know before hand if an engine has these types of problems,.. so that a patch to the programming can be done, and a possible failure like yours could be avoided? How can one predict this BEFORE it happens and it is too late?

On the oil side of things, One thing that can be done is to ensure that there is not too much wear in the upper end of the motor, and that there is plenty of oil pressure too. This can ensure the pistons have their best chance of being cooled properly, but no one can see inside the engine and observe the oil flow to see if it is correct,.. especially around a piston that has possibly suffered a lot of soot packing etc. As well, soot and oil deposits get into the underside of the piston and coat it over time, reducing its ability to keep itself cool, especially on the exhaust side where it gets less oil flow.



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On the programming side of things, If someone simply gaged it based on on age and wear,... well that is not accurate in itself, ... I have seen UN-Mandated MM engines with upwards of 800 horsepower in them, burning clean, pushing the limits of all the mappings at a million miles+ have no issues whatsoever, -- .. so age alone can not be the determining factor,... So What should one look for? -- That is the question...


Personally, I think it cannot be predicted without extensive testing of injector spray pattern etc. -- or at the very least,.. boroscoping the engine to see what it looks like inside the combustion chamber(s) before hand. Even then,.. It would be difficult to spot on a sooty engine.

The only thing someone can hope for at best,.. is to perhaps sharpen the curve on the mappings based solely on engine wear and blow-by? instead of using a single offset. -- Doing this could potentially reduce this failure possibility on some trucks,.. but there is still no miracle cure no matter what you do if it is bad enough.

-- No matter what,.. It simply is a risk (patterns of failure show about a 3-5% risk) in the end. All one can hope for is to minimize that risk,.. so from now on,... I would think that using a curve in the mapping,.. The older the engine, the sharper the curve,.. would be all one can do and hope for to help prevent an aged, worn engine with uneven patterns from malfunctioning in this way, but that no matter what,... there is always some possibility.

Combine this with ensuring the oil has good pressure and that there is not too much wear in the engine overall that can reduce oil flow to the cooling nozzles,.. and that is the best one can do to try to help reduce/predict the risk factor for a particular engine.

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Keeping your fuel system absolutely clean,.. and keeping soot out of your engine is anyone's best hope for preventing this type of low compression, bad spray-pattern, reduces oil flow type of failure,.. MM or not. -- It is too bad no one takes it seriously enough to actually go through preventative steps the moment they buy their truck (when it is still new),.. but instead, wait until the engine is suffering from lots of problems before even considering doing things like using smaller, finer filters for their fuel,.. and using a non-abrasive fuel injector cleaner once a month (Like diesel-kleen),.. and then installing a decent bypass filter to keep the soot out of the engine and oil.

The CM871 is the engine with the most types of these failures by far, even above the CM870, .. And it is also the one that suffers the most soot damage and has the most soot going into the oil pan. This is no coincidence!. -- Considering this,.. Some program changes to higher risk engines can be made,.. but nothing is ever going to stop these possibilities from happening completely. If your engine has an uneven injector pattern, and has reduced compression due to age/wear,.. a failure like this is likely to not be predictable in the end, but there is some hope for reducing it if you are at high risk when you get custom tuning done.

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If your one of those guys sitting there reading this and your thinking about a "Mandate Removal",.. you need to consider heavily, that there is always risk to such endeavors,.. and yes,... there is always that possibility of something like this showing up after. -- It is not based on one thing or the other,.. but a combination of things that cannot be predicted.

A lot of trucks are purchased used, and the damage form excess wear and bad, clogging injectors is already done long before the truck got sold!. -- It is truly a shame indeed, the abuse these trucks suffer from during their earlier Mega-Fleet abusive ways where no one cares, because they know they are getting rid of the truck before all the problems show up. Most of them do not change the oil regularly to keep soot down,.. and none of them will spend extra money on bypass filters,.. or injector cleaner,.. unless it is too late for the motor!.

What a shame indeed,.. as most owner-ops these days buy trucks that have been abused in this way,.. and no one can predict what the outcome will be in the future, nor how long the truck will last before that inevitable "Inframe" comes along to bite you in the arsse!.