As I've stated, I fully understand how the MDS lifter works. And I am correct in my explanation.
I don't believe that's the case.
Oil pressure is used to unlock the pin.
Yes, oil pressure is used to push the pin into the body, allowing the internals to collapse. You originally claimed:
As with GM displacement on demand systems, oil pressure is used to push in the lock pin and allow the lifter to collapse in on itself. Likewise, oil pressure is used to expand the lifter until it reaches maximum extension and the locking pin is flushed in place of its hole, and oil pressure returns to normal lubrication.
That's inaccurate. Oil pressure is used to activate the collapse function. Oil pressure is removed when MDS is disabled, which results in the pin sliding back out as the lifter cycles, locking it back into place and resuming normal operation.
But what you are missing is what happens when the oil pressure is stuck open? Does the solenoid know that? How does the computer know when to stop supplying oil pressure to the lifter despite the lock pin engaging or not? Understand?
If you ask me if I "understand" one more time I'm going to lose my mind. I have been exceedingly polite in this exchange, please don't turn this nasty.
You are vastly over-complicating the function of the system. It's exceedingly simple, and no, the computer has no idea if the lifters are collapsed or not, it assumed they are when the solenoids are activated.
- Solenoid OFF, MDS OFF, the feed tubes to the lock pins is unpressurized, lifters operate normally.
- Solenoid ON, MDS ON, the feed tubes to the lock pins are pressurized, the lifters collapse.
This is readily visible in the bloody video you linked to. The solenoids stay "live" while MDS is engaged. They turn off to disengage it. There is no split solenoid scenario where the pressure is reversed to re-activate the lifters, they are reactivated via the internal spring located behind the pin, visible in the pictures. The oil pressure is used to deactivate them and keep them deactivated.
The solenoid does not simply supply a 1 to 2 second burst of oil pressure to unlock the pin. I've already spoken to a Chrysler Tech who was trained on this engine, and it DOSE INDEED use oil pressure to help expand the lifter. The spring is there for additional force to help speed up the process, but it is also there to keep tension on the upper and lower ends of the lifter to prevent lifter floating.
The solenoid stays active the entire time MDS is engaged, as I've indicated above.
The yellow section is most certainly not stationary, it's the BODY of the lifter, it follows the profile of the cam lobe!
The upper end of the lifter as seen in my illustration below shows the moving parts and the stationary parts. The yellow line represents the hardened stationary point. The red line shows the moving part. This clearly shows that it is possible for a lifter to rotate internally since there is really nothing there strong enough to prevent inadvertent rotation. But as you've suggested, it can rotate from the top as well since they are held in place by a plastic keeper held on by I believe a 10mm bolt. At any rate, the internals are collapsed when the lock pin is pushed inward, but the roller and body itself can rotate if the plastic keeper fails to hold the lifter in place. My buddy that works at Chrysler seems to think this is what's causing some lifters to rotate (to also include the Hellcast engine). As for the roller bearings, he believes the problem is caused by lack of lubrication mostly caused by MDS.
It's what the roller is attached to, and the roller is constantly following the lobe profile. The part that BECOMES stationary when the pin is displaced is the UPPER portion of the lifter, which basically resembles a tall piston, and the internal spring, which you've captured in your orange line, is there to keep pressure on it so the pushrod doesn't get bumped out.
If the internal piston assembly rotates (which it appears to have in your engine) then it may prevent the pin from being displaced, thus preventing that valve from participating in MDS.
And if your buddy has confirmed that the bodies are rotating due to the plastic guide, even in the non-MDS HellCat engine, then that simply compounds my 6.1L and manual transmission non-MDS examples and again shows that the problem isn't MDS-related.
Now back to the oil pressure. One thing you might have overlooked is what happens when the lock pin is stuck open? I believe oil volume is lost there,
To where? I covered that in the post you are replying to here. The lifter isn't a black hole, it's a fixed volume assembly, and that volume is SMALL. There will be leakage around the body, but there is always leakage around the body from normal lubrication, so I can't see this having any real impact.
and that would explain why the 2 non-MDS lifters were not as saturated as the MDS lifters.
Because they don't have a hole in the side that gets filled with and hit with oil. It isn't going to take a lot of oil for them to look significantly "wetter" than the ones without the big orifice in the side of them.
Unless you want to explain this away with another cause, perhaps a clogged oil passage or faulty solenoid, how else can you explain 2 saturated MDS lifters both with open lock pins, and 2 nearly dry lifters which are both non-MDS? The answer is quite obvious to me. Oil is being lose to the MDS lifters and starving the other 2. This again is basic physics 101. Pressure is constant throughout the system unless their is a compromise. The problem is identifying the compromise.
Yes, if you got in there with a hammer drill and put a 1/2" hole in the MDS lifter gallery, you would cause a system-wide loss of oil pressure. But given that the MDS lifter hole dead-ends, that's not what is taking place here. They are wet because they have a hole in the side and it fills with oil. The non-MDS ones are not as wet because the bodies of those ones are lubed through the pressurized hole on the lifter bore, and thus there is no hole/chamber for oil to leak out of and cause them to look more "wetted".
And yet nobody on here seems to offer any suggestions of what's causing the compromise. And no, long idling is not considered a compromise; that is an operation and not a system. If an engine can suffer catastrophic failure from long idling, then we would be seeing both intake AND exhaust lifters being wiped out.
I think this part needs more research. How many folks are actually tracking whether the lifter is intake or exhaust? I'm not going to bother Googling it tonight, and I'm not going to ask my buddy at the dealer because I'm 100% sure he never checked.
So to summarize the questions I ask of you in a friendly way:
1. How do you explain oil saturation on failed MDS lifters?
Already answered that above.
2. How do you explain low oil saturation on non-mds lifters?
Already answered that above.
3. Are the MDS oil solenoids timed with regards to pressure? Or do these solenoids react to back-pressure (as in when the MDS lifters are lock, thereby increasing oil back pressure, and thus closing off the solenoids)
Neither, and this is why I don't think your statement that you understand how the system operates is correct. As I noted earlier, the system is quite simple, when the solenoids open and pressurize the feed tubes to the orifices, displacing the pins, MDS is active. When they shut off, MDS is disabled, as the pins self-seat due to their spring-loaded nature.
4. If MDS lifters are not the problem, then why is there a huge 2 to 3 month backlog of lifter replacement?
These are very direct questions that require best guesses based on sound evaluation and examination. I look forward to your reponses.
Didn't you just state to Dave:
But right now, I'm stuck on hold as I have to wait for those pesky Hellcat lifters which are back-ordered to fix all of us "rare" engine failure victims.
So why are the non-MDS HellCat lifters on back-order if the non-MDS engines are immune as per your original posit? (despite the ample evidence I've presented at this juncture with examples of the 6.1 as well as both the 5.7L and 6.4L manual transmission cars without MDS also having the problem).
Dealers aren't putting HellCat lifters into engines in for a standard lifter replacement, they are using the OE parts, which would be part numbers:
Both of which are in stock BTW.
The non-MDS lifters are part # 5038784AC (not in stock) and the HellCat ones are part # 5038787AC and also not in stock.
So, unless there is a rash of HellCat lifter failures (unlikely) I'm going to conclude that this is just a supplier shortage at this juncture. They have plenty of stock for direct replacements on their most common engines (MDS ones) and the ones on back order are for the manual-equipped cars, the 6.1L and the HellCat.