S-Prihadi

CORRECTION : M278 does not have this diverter valve. My bad. Title been corrected

I was inspecting mine, Bank 2 only due to easier access, so I am sharing.

This diverter valve is known to leak overtime from tearing of the silicone membrane. You then loose boost. Made by Pierburg













Installation depth is 18mm.




The 18mm shown by the caliper is where the "piston's top seal" will park itself when installed.
18mm is also the position if you want to test the magnetic coil pulling down on the piston, more than 18mm the metal section of the piston is too far up and magnetic field can't pull it down.




Position. B1 is Bank 1, so B2 is BANK 2 ( Left Hand drive car driver side )









Audi/VW engine due to high population count and they are mostly turbocharged, uses this type of diverter valve too and is easy to get info on them on Youtube.


VW/Audi has done so many revisions on this component. I believe the piston diameter is smaller 22mm there about.

Too bad our MB seems to use the older design which VW found not so robust


Its a simple ON-OFF switching by ECM. 2 wire connector. No fancy frequency or PWM duty cyle yada yada. This diverter valve uses 1.2 amps at 12V.

My test

kistiyanpetrov

good topic, any idea how i can notice if my "diverter" valve is not good?

I do half boost or maybe for an moment a bit more but not more than 3/4 on the AMG gauge screen, I changed transducer valve + pcv valve (with the orange diapraghm on the vacuum pump) car is better in terms of performance but still same boost is doing and idk what might be..

I tried myself to unscrew the diverter valve on Bank 2 to check if something is wrong with it as you stated above but i didn't manage to do it, it's really hard to unscrew it for some reason.. i can't imagine how difficult will be to be unscrewed and to reach to it on Bank 1..

S-Prihadi

Kis asked : any idea how i can notice if my "diverter" valve is not good?

That is a tough question if you do not remove the diverter valve for proper inspection.

While a diverter valve is not a boost control mechanism like that wastegate vacuum actuator controlling the coin shape wastegate at the turbo, it does control boost too but not for peak boost, but rather not to waste
boost and prevention of unwanted shock-wave at the turbo. Go to page 15 to 17 of the M276.8 engine information document. Attached full PDF











Now, this diverter valve is a NORMALLY CLOSED valve, different to the wastegate coin shaped metal "door" at the turbo which is loose if not supported...and we can call it as NORMALLY OPEN valve.
The nature of the operation of the wastegate vacuum actuator is also a NORMALLY OPEN, this is for safety reason for sure... safer to be under boost than to explode the engine if over boosted when and if
the design of the wastegate system is a NORMALLY CLOSED one.....and it failed.

The diverter valve has a spring to fight or keep shut the polymer seal as per the design pressure of the turbo plus some extra. How many PSI/BAR, I do not know.
One thing for sure, my engine M276.820 is only a 0.8 BAR max boost, a C43 with higher horsepower M276.823 could be like 0.9 to 1.0 BAR.

By logic , if one is to design a mechanical spring based Normally CLOSED diverter valve with electrical assist to open the valve sooner than what the spring would do on its own,
it would be a few percent higher only than the maximum pressure of the turbocharger...again as safety measure.
So if say my engine is 0.8 BAR max boost, I think the engineer would choose the divert valve to have a counter spring to be no more than 1.1 BAR which is already a lot.
0.3 BAR increase from a 0.8 BAR is 37.5% increase and that is already decently plenty.

In an event one tune the car say to 1.5 BAR max turbo boost, that diverter valve spring overtime would probably be weakened if not the seal get damaged.
It probably wont be an instant damage/defects at such modified increase boost, but overtime the diverter valve which is not design for 1.5BAR, would surrender and goes leaky

kistiyanpetrov

Thanks again for sharing feedback on this topic

I've really strange behaviour when car is on Comfort and on higher gear if i press bit more the throttle is trying to build boost almost to MAX as you can see in the video below, but if is on lower gear and higher RPMs (2100 for ex) is not doing full boost (when throttle is pushed to the floor) so I am really confused why this might happening

Also does both turbos are working constantly or one is for lower RPMs and other one is for higher RPMs?

Either not sure if car during building boost can loose boost through the diverter valve, i will try soon to dismount both of them and check if the rubber seal is fine

S-Prihadi

Our engine is torque limited by the computer.
Your must understand what is torque in respect to horsepower.
Read here : https://www.caranddriver.com/news/a1...he-difference/


This is your engine calculated torque and HP chart. I say calculated because I do not have MB official document on it.





This is my engine official torque and HP chart. My engine is M276.820 and yours is M276.823




So your ECM would want to keep your engine at maximum 520NM of torque, as to not damage it.
When at low RPM, this is your calculated engine HP output



So when at low RPM, the room for torque limit is still available, your engine would boost more to achieve that.
If at higher RPM the high torque is easily available already and limit can be reached easy, so no need much turbo boost anymore.

See my engine log below. It is 5 data points per second.
The high boost are at the lower RPM mainly, because that is how MB set the engine to be.
As long as in cold enough weather say 25C and engine is not heat soaked , if you can hit 95% of your engine target boost level ( MB setting ) during a 1st, 2nd and 3rd gear WOT to redline,
there is no obvious leak anywhere on your system.

Do not ever think the boost can stay high all the time, no.... that is not how our engine behave.





Data point region 2500ish




.
Data region 7,700 ish






This one using Xentry and I can see the torque in Newton Meters.








Go and test your engine WOT-Redline in 1 to 3rd gear. Log it with a logger at least 2Hz data points and see what is the result.




Drive safe...

kistiyanpetrov

The difference before the ECU/TCU updates is that now car not produce the full boost with the remap which i am with right now (and before the updates was the same remap) i don't get why before was hit full boost all the time no matter if car was on higher RPMs or lowers no matter of the gear (2nd or 5th).

Since my car don't have CPC there shouldn't be some new added limit on the ECU/TCU somewhere for the Nm/Tq isn't it?

That makes me to think what could be wrong currently, please check both videos below


P.S. I did another video with brake boost if this can bring some clarity, unfortunately i dont have obd scanner so i can't pull the data for now which you asked above

S-Prihadi

Does not mean you car is not getting that anti-naughty CPC module like newer cars...............MB can't protect their engine computer and tranny computer with a newer software.
Even engine Start-Stop kill feature took years for 3rd party scanner to be able to KILL the feature, which was actually a simple non protected variant coding.

Get your tuner to do his homework based on the latest update software you got from MB on your 2 computers.
I am sure you have a proper decent scanner or some sort of BLACK-BOX which can read such information ?

Also do not trust a 100% what the display is showing you. Use OBD2 based data reader and read direct from the engine computer.

============

If there is another device in M276 3.0 Turbo which can leak a boost, it is the duo check valve at the intake manifold, which is for injecting fuel vapor from tank and oil vapor from engine crankcase.
Read here : post 79
https://mbworld.org/forums/e-class-w...ml#post8849390

kistiyanpetrov

Unfortunately i can't go to him because he is based in another country and is really painful for me to travel for 3rd time to him (i went 2 times back to him only because the car was more than great and this software on the car was for 2 yrs) and now after the update he don't know what is happening and the final result is not the same as before

I just remember i have this photo with what was updated and i tried to find info on the software versions which are updated to look as ref what contains the update but i can't, do you think i can find somewhere such info on this?

Today i was about to check with mechanic live data but was rainy and i didn't go but in the next days when im free i will jump to him, but he have some obd scanner not Star diagnostic, so not sure what exactly to look on this OBD scanner and to send to you?

Here is the image Xentry from dealer prev/current versions what was updated

S-Prihadi

So....W205 gets N127 - Control unit POWERTRAIN - PTCU
This is probably an early generation of the CPC.

Find attached the information on N127.
Basically N127 is a gateway and that is NOT GOOD for anyone trying to mess with software.

Sorry I can't help you further. software is not my thing.

ADD : My W212 does not have N127. As far as I know, no gasoline W212 gets N127. Its a new thing for W205 and W213 before newer CPC module during facelift ?, I guess.

kistiyanpetrov

Thank you, yes it might be idk either, that's why i was curious what contains this SF update, i found recall for Powertrain and ECU on W205 which the codes matches with my Xentry, but not sure why and how is affecting the boost, i found another guy who have the same situation as me, he had the TCU update and since then don't have full boost and can't find the reason (this is on stock map)

The ECU N3/10 update is about some emissions to heat catalyst on every start up on the car (which I notice that everytime when i start the car even if i drove for 2h and turn it off for 5-10min will idle to 1400RPMS really annoing) - https://mb.oemdtc.com/1096/update-en...lass#more-1096

The TCU N127 update is about - the powertrain control unit may not correspond to the current production specifications. It is possible that the next maintenance interval is displayed to the user as a negative distance reading in the instrument cluster.
https://mb.oemdtc.com/1652/update-po...lass#more-1652

S-Prihadi

Well, MB may have written other things in the software while at it

They won't tell you the color of their "underwear".... LOL

Emission and Power are mortal enemies. This we have to remember.

kistiyanpetrov

Yes for sure, i really get so annoyed when i went to the Dealer to get my car from Service B (and before i left it i told them don't touch anything else apart of the servicing oil, filters, spark plugs) and when I look the face on the Service Manager it was proper guilty one that he did something that it shouldn't and when I jump on the car and went off the CEL appear and i told myself | "i knew it.." and on the next day i went back and they told me yes you don't have catalyst is normal to have CEL and i asked why did you touch Software without my permission? and he was oh sorry we can't do anything this is what we should do bla bla.. so for 6 months i can't figure out what is happening.. and i really get a bit sad because my car was more than enough powerful and enjoyable :/

Apart of that, after you saw my videos do you think there's any chance some of the Diverter valves can be not fine, i will check them anyway when i've time but just to see your opinion on this

S-Prihadi

I can't comment on your diverter valve possible issue, merely from that video, unless the diverter valve is fully torn and you wont get boost at all.
If its spring gets weaker due to non standard boost, well it can reduce your tuned boost request.
However, if the drive-ability of the car is good as stock car, I believe all this is from software "lock".

If new software is so concerned about emission, missing the CAT and getting CEL is a big deal for the engine computer and probably N127 too.
Emission matters is what car manufacturer fear the most.... more so in USA and California.

kistiyanpetrov

Will see, if i've any updates on this will post it here in case someone else have same problem (hope no one)..