kevm14

Original post below. Scroll down for frequently asked questions.
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So I came up with a new thing to be worried about. This isn't really a new issue but one I haven't seen people discuss much on here.


Evidently we have 2 stage oil pumps (unless that solenoid is PWM controlled, then it's just variable). The short of it is, oil pressure is decreased in no/low load situations freeing up parasitic loss and increasing efficiency by some probably infinitesimal amount.

Well, the solenoid can get stuck in the open position (low pressure mode). I believe this can lead to certainly the cylinder scuffing but also just total engine lockup. I read somewhere that you can just unplug the solenoid and as long as it is not already stuck, it will never actuate into the "low oil flow" position. Aside from general thoughts about this (I don't see a mechanical downside though), I am curious if it sets a CEL.
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FAQ
Q) What is the oil pump pressure control valve?
A) On a wide range of Mercedes engines since model year 2011, the oil pump has 2-stage pressure control. There is a normal pressure mode where it works like a normal oil pump, and a low pressure mode, to increase fuel economy by reducing parasitic losses from the oil pump. This lower pressure is achieved by a valve or solenoid that bleeds pressure from the pump, lowering pressure when activated by the ECU.

Q) What's the problem?
A) Watch the video above. They can seize and cause engine failure due to inadequate oil pressure.

Q) Doesn't the ECU know what the engine oil pressure is?
A) On most engines, NO. On a selection of applications, there is an oil pressure sensor. Low oil pressure mode is done blindly on engines without a sensor and it's not clear that the sensor is used as a feedback mechanism even on the engines that have it.

Q) A seized oil pump valve sounds uncommon. Why should I worry about this?
A) It turns out that even when the valve is working as designed, low oil pressure during a range of conditions can lead to some of the following issues:
- Rough idle and generally unsmooth engine operation
- Imprecise cam phaser operation, leading to roughness, lack of response, and other unsmooth power delivery
- Reduced piston squirter operation when oil pressure falls below the threshold for their operation, which is MUCH more frequent when the valve is being actuated by the ECU. This is thought to be a contributor to cylinder wall scoring. Piston squirters spraying more frequently add more lubrication to the cylinder walls and provide more consistent thermal control to the pistons. Dimensionally stable pistons are much less likely to score the cylinder walls!
- Poor transmission performance, including MCT engagement roughness on AMG applications

Q) But my car seems to run well! Surely this doesn't impact me, right?
A) Wrong. See above. Even cars that were otherwise running well benefit from unplugging. The effect won't be identical across all applications but the general trend is everyone sees positive results immediately. There may be additional benefits that accumulate as you use the vehicle, such as fuel trims relearning and updating.

Q) I'm scared to unplug something related to the oil pump. How can I be sure this is safe?
A) A few reasons. First, there is a Mercedes TSB on M274 applications for a code related to the circuit being open due to oil in the wiring harness for this solenoid. The TSB says the code will not illuminate the CEL and that the solenoid is NON-ESSENTIAL. Two, the valve mechanically is designed to failsafe in the high/normal pressure position, because there is a return spring that closes the pressure bleed ports when power is removed. Third, because the engine clearly runs, sounds and feels better with it unplugged, which is the conclusion of an ever-increasing number of participants in the unplugging revolution.

Q) If most applications have no oil pressure sensor, how do we even know what the solenoid does?
A) Because some enterprising folks with M276 engines tried it first, and documented operation. The exact valve and strategy is used across a wide range of engines, so results were extrapolated. Also, operation and purpose of the valve is well documented in WIS.

Q) What if I don't have one of these unicorn applications with an oil pressure sensor?
A) You can measure oil pressure manually if you like, per WIS instructions. Generally, Mercedes engines have a test port on the timing cover, but it differs by engine family.

Q) So if I unplug, then my engine will never fail, right?
A) That would be nice, but no, this is not a guarantee against engine failure. What it DOES do is decrease the chance of a LUBRICATION-RELATED engine failure, which is certainly worth something. Also, unplugging means one less source of oil in your wiring harness. It isn't just from the cam position sensors and cam "magnets." Except your engine won't run (properly) if you unplug those...

Q) OK, I'm convinced, I want to unplug. What do I do next?
A) Locate your plug and unplug. This section will be enhanced with some guidance per engine family. Lots of info is buried in the thread. Alternately, user kenneyd created this helpful video:
Q) Is there a poll or something that could be used to capture who has already done this and what their experience has been?
A) Yes!! Take the survey here: https://forms.office.com/r/1LB564Zr6i

View the results here: Survey results

Still under construction - links and other supporting data will be provided later.

WANTED!!

Try it. However, I suspect it will trigger a cell and put the car in diminished power mode to protect the motor because the ecu can't see it vs it getting in the stuck position and not throwing a code.
I'm of similar mindset as you in that oil pressure under no load is not a bad thing.

CZ 75

Maybe it’s possible to code it out? Or modify it to always open?

kevm14

Do these still not have oil pressure sensors?

If not, the control strategy would already assume that the plunger springs back to closed. When presented with the information that "oil pump is locked in full flow position" I don't know why it would go into a limp mode. I could see a CEL though, but maybe it would be a silent code. If it doesn't trigger the CEL, then I could still pass OBD-II readiness, which is what I really care about.

WANTED!!

I thought I said that in my response. If not, I'll restate. I'm betting when they get stuck, the ecu doesn't care and won't trigger a cell. However, I'm thinking if the ecu can't see it at all, it'll throw either an active or passive CEL and take an engine protecting action. The only way to know though is to try it and report back.

kevm14

My plan was to attempt at next oil change.

Here is my hypothesis:
- It will set a code of some kind. It might be a silent code, though (no CEL), which is what matters.
- It will not do any kind of limp mode. The ECU does not "increase oil pressure." It only stops decreasing it. If there was an oil pressure sensor it would just see oil pressure and probably not freak out. How many cars actively shut themselves down due to low or no oil pressure? None or not many.

vich3

Check out this thread on the W212 forum
It will give plenty of info on this topic


https://mbworld.org/forums/e-class-w...en-passed.html

PeterUbers

nice... if @S-Prihadi can't figure it out ... I don't know who can

kevm14

I skimmed it. The gist seems to be unplugging is still a good idea. No limp mode, no CEL. The hardest part is actually unplugging which may be difficult. I don't even know where it is.

Mojo20032004

Those look almost like the bmw vanos solenoids.. I know on the n54 n55 335s, when these clog up or go bad, they cause all kind of issues... Stay ontop of oil changes, don't follow the stupid 7-10k Mercedes recommends and you don't have to worry about clogs

kenneyd

Both interesting post, interesting video.
Essentially sounds like our engines have the equivalent to a Widowmaker artery.

I read through the post, I did not see any explanation of why Mercedes engineered this way. Not that I was expecting us to know exactly why, but does anyone even have any good ideas of why Mercedes engineered it this way?

Seem like one guy just unplugged it, and the other guy was trying to figure out a harness with resistance to fool the ECU to think it didn't need to be opened.

My understanding is they were looking for somebody to dig into the ECU to figure out if the parameter could be changed, did not sound like anybody had actually looked into that yet. I'll search through the ECU to see if there is a perimeter that even can be changed

ImolaSix

It's all for miniscule efficiency gains as mentioned above. It's sucks that the infinitely variable vane oil pump gets constrained by a cheap two position solenoid. Most of the new engines have the same style pump but with infinitely variable actuators for much more precise control based on load and temp.
Hoping someone figures out if unplugging is viable, as having the piston oil squirters running helps tremendously with getting the oil up to operating temp in the winter months.

kevm14

Wouldn't it be wild if this was a major contributor to the mysterious cylinder scuffing?

That thread suggests that it is PWM controlled on the M276. I don't know if that means it is also PWM on the M278/157. I saw something like 10% duty is off and 90% duty is on. With no oil pressure sensor feedback, that whole deal seems totally ludicrous to me. I remember learning my M113K didn't have a pressure sensor after I learned about the oil pickup O-ring of death. This is kind of the same thing, all over again, 10 years later (model year)...

Good point on the oil warmup. I have noticed that during warmup if I need to power past some traffic, the oil temp picks up REALLY fast. That seems to confirm that perhaps during lower RPM and lower load the oil pump solenoid is dumping pressure until I ask for powah.

Another benefit I thought of is no oil wicking from this particular device. I thought this was another one of the troublemakers for oil wicking. That's a lot of benefits from unplugging a solenoid.

On the silent code thing, I already have a silent code because I have my intercooler pump running full time. There is a code but no CEL. This should be the same deal. I have not been through emissions with it like this, though. That said, I think there's a chance the code can be disabled entirely if it was somehow a problem.

ImolaSix

Extra lubrication on the cylinder walls would definitely help with the scuffing.
Another advantage would be having more oil pressure on the big end bearings to reduce connecting rod "rocking" from the piston driven rod design which I think is a major contributor to the wall scuffing.
​​

WANTED!!

I'm still not a full believer that a silent code associated with something like this doesn't do something where the ecu reduces power to some extent. No one in the other thread neither dug enough into the coding or did a before and after dyno comparison to be certain. My point being, it sounds great on paper but I'd like proof before I simply start unplugging the solenoids or videamo coding without fully understanding the "yes/no" parameters associated with that line of coding. I'll let smarter brains than I start playing with it.

Also agree that this is a likely contributor to the cylinder wall scuffing. It's either a lubrication issue, or an overfueling issue causing cylinder washout.

kenneyd

Agreed.
Oiling is an engines most critical system.
Messing with this system it should be done with extreme caution. A simple misunderstanding of the function of this system can cause catastrophic failure.
Don't get me wrong, I've messed with a lot of systems, my e63 HX pump is wired always on, I converted my 355 to manual trans and my 430 I've modded all kinds of things etc.

IMO, more oil is better... But I'd just want to really no the reason before I change something that seems so intentional.

If anything, it reinforces the need for good clean oil, I generally do half intervals from what the factory recommends

kevm14

I can dig around in WIS.

Whether it is a 2 stage or PWM modulated, as far as I know and from what that thread described, the plunger opens to relieve/bleed oil pressure. The more open it is, the less oil pressure you have. And the default state is closed/full oil pressure. Also as far as I know, there is no oil pressure monitoring but I need to confirm that. I know those Germans do crazy things but assuming the ECU changed strategy due to "loss of control of 2 stage oil system," I would expect the reaction to be noticeable. Rev limit, power limit. It would not make sense to change the operation of the engine in a way that is barely noticeable (like 10% reduction in power). Furthermore, the reason why they probably don't do this in the first place, which I have said from the beginning, is because it is supposed to be a mechanically failsafe design. They have no choice but to assume full oil pressure if unplugged. Why? Because there is no operation of the solenoid that increases pressure (briefly the other thread thought it did but later they proved it did not).

kevm14

Initial thoughts:
- We clearly don't have an oil pressure sensor (STILL) due to the procedure for checking oil pressure (an oil pressure control system with no feedback loop is still insanity)
- Operation of the "oil pump valve" (component Y130) matches what that thread was saying. And it's for fuel economy.
- If it is even possible to access, it should be roughly on the lower right (or is it lower left??) of the engine, sort of near the crank pulley, timing cover area
- Spec oil pressures are identical across M276, M278 and M157.

ImolaSix

25-35psi is the normal range for 2500rpm?
Considering when tuned these engines can make 700+ ft/lbs at 2500 rpm, that's definitely on the low side. 5w50 might be a consideration for tuned guys.
Unless that range is just while in Park under no load? Maybe under load the solenoid opens and ups the pressure?

CaliBenzDriver

yes, please find where in MONACO Tool this control can be worked out.
Until then I am going to enjoy amazing torque with my quick shortcut.

CaliBenzDriver

one of the nasty issue is piston cooling being disabled below 20Psi... cracked pistons scoring cylinders are the end results of poor oiling.


In addition, poor pressure available to VVT makes them uneffective, poor torque below 2,000.RPM

This is a good source of laggy performance... specifically when you compare before/after.

This is EXPERIMENTAL and primarily interesting for people who understand what's at stakes here. Your engine, your research, your decision how it may fit in.

CaliBenzDriver

++++++
Couple ounces of straight truth to help simplicity:

the dual-rate pump is controlled by On/Off solenoid.

there is no regulation taking place, two rates only

Solenoid Off is 10% PWM to monitor load is present

the default pump resting rate is normal pressure

Pump is not an upgrade "normal/high" pressure

Pump is a downgrade "reduced/normal" pressure

pump is shifted to low pressure by active solenoid control

when solenoid is resting, it is shut closed.

when solenoid jams open --> hot pistons RIP!!!

Piston are spray cooled by squirters that only open above 21psi.

Piston sprayers are closed below 21psi to preserve pressure for journals

Unplugging pump does not CEL, only a quiet code.

VVT does not operate well on low pressure

Tensioners require pressure to counter camshafts

HPFP(s) rolers benefit from lube and cooling at engine least lubricated location.

Tested ECU MED17.7 comands low pressure below 3500.RPM under normal load

Highway speed is around 2000RPM ie. low pressure at 70MPH

Oil circulation delivers anti-friction film and carries away heat

MB is not alone sporting this Bosch innovation.

Hope this helps enjoy your ownership


++++ missed the mark
With only one oil pressure sensor ECU could easily prevent catastrophic engine damage when solenoid valve jams open. ECU would easily limp mode on low pressure!
Solenoid could help regulate pump output pressure to guarantee good lube/cooling.

++++ Casualties:
Every parts relying on oil cooling and lubrication is affected by reduced delivery. Catastrophic failures are the final straw. (pistons, VVT Gears, camshafts, HPFP)

Black burned oil is when it needs to be replaced,

kevm14

Alright, forgive me if I'm slow but....did you unplug yours already or something?

CaliBenzDriver

Yes, I am one of the original pair of researchers.... I unplugged as soon as I realized my engine oil pump was kept on low pressure most of the time while driving.

I am a computer research scientist who enjoys the reality of hands-on motor controls.

TT-V8 are subject to extreme heat, specially with reduced oil circulation.
The original study was done on a TT-V6. It's only a straight extrapolation to think the V8 is identically managed.

Here a list of issues I attribute to limited oil pressure:

1. Bent rods !!
2. cracked pistons
3. scored cylinders
4. flat HPFP rollers
5. shaved cam lobes
6. breached CPS "oil-in-harness"
7. failed VVT's (Bank1 intake!)
8. limp chain tensioners
9. blow-by leaking seals galore
10. oil filled vacuum pump
11. oil filled turbo wastegates diaphragms
12. oil filled intake plenum
13. carbonized valves
14. contaminated lambda/cats

> HOW TO EXPERIMENT...
There are multiple ways to disable this engine killer.

1-- I simply pulled the plug and have not recognized any issue since driving without reduced oil pressure.

2-- I am a software developer who is not setup to mod Bosch firmware code. I can only hope this solenoid feature may be reprogrammed with a free patch because cord-cutting is also free.

3-- It would be easy to cut one of the two solenoid wires directly at ECU connectors


> Beware of jam... RIP:
-- We could think pulsing this PWM solenoid with pressure control would help make things great, NOP! This is actually dangerous!
A "Low oil pressure" jam guarantees engine blow-up RIP the 1st time.

-- ​​​​​​This cheap solenoid valve is subject to jamming in open position. This takes place when foreign debris accumulate internally blocking the plunger.

-- Pragmatically this failure mode is another nail in the coffin to let it rest unused. This is a poorly implemented killer feature without control feedback.

-- The scary testing is to drive around until engine blows up Cyl.1: RIP - As the original co-researcher, I sided with nomal oil pressure!!



> WHY... so much engine improvement?
-- The first thing that strikes after safely canceling low pressure is smooth power.
Great all the moving parts that were mostly dry are now well lubricated but there's more...

-- The engine has new amazing torque at 1100.RPM and it keeps getting better as ECU relearn the base mixture and lambda are getting cleaner.

-- Engine now has serious torque where it used to be laggy.

-- After 1,200.Miles relearn I realized the gas pedal is now super responsive. The engine has solid torque up/down California hills. What a transformation that is!! Terrain now feels flat.

-- Another oddity: I noticed that even the brake pedal has grown more touchy.
We know brake booster is operated by a vacuum pump driven by bank2 intake camshaft.
The only explanation I have for increased vacuum is less pump internal oil and less crankcase pressure to counter act chamber vacuum.


++++ Links to Original forum knowledge ++++
Link about lucky DTC

Original root research about pressure

I had my doubts testing...



I luv NT-Kernel with a passion
I enjoy Bosch CAN-Bus architecture
Enjoy your research journey !!

JettaRed

iTrader: (1)

Nope. No CEL or limp mode. Actually, the car feels stronger on the low end. The solenoid is normally open (full flow) and is restricted only below 3500 rpm. You will get a DTC P06DA00 (open circuit), but not a CEL/MIL. Mercedes has even issued a TIP referring to the solenoid as "non-essential". Not sure where the wiring harness connects on your engine, but on the M276 it is right in front next to the crank pulley on the right side of the engine.

All you ever wanted to know and then some: https://mbworld.org/forums/mercedes-...ml#post8878558