CaliBenzDriver

there is a super easy way to do this:
read the XENTRY cam position while someone manually spins crankshaft.

Remove the coil power so engine doesn't stand a chance to startup during manual crank with ignition ON...

Concentrate first on Bank1 intake.

S-Prihadi

Nika,

Your VVT-s 3 of them are bad already. The only decent one is EXHAUST VVT Left Bank or Bank 2.




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Too bad your Open Port is really slow ( mine too hahah ) and the data is only 2hz.
If it is the typical 7hz, we will see more dancing I guess

See the zip file. I done the work for you.

S-Prihadi

Proper warm idling RPM should be like this for VVT action. Not too much drift. See data point 300 and up, that is idling.
Also see I get 900 ish data point and not 200 ish for the 120 seconds log. For idling the OpenPort 2 is OK, for for actual dynamic tracking is too slow and can make us come to wrong conclusion.
I almost got screwed by OpenPort slow-ness too , if for VVT monitoring.






..

S-Prihadi

Nika,

I am zooming the graph to represent 3 degrees resolution for the 2nd lower graph.




We wont get 0.5 degree accuracy between SET POINT ( Commanded ) to ACTUAL when engine RPM is not stable, or engine still COLD.
My engine is M76.820 3.0 Turbo, so my VVT set point is not the same as yours the M276.9 3.5 Normally Aspirated.

Our ECM can adjust to chain stretch or tensioner weakening, up to a point....using the Adaptation.

What ECM can not control is leaky oil at VVT vane or loss of locking mechanism .
So ACTUAL degree value tends to do its dancing more and more ( higher degree difference ) as the VVT has more wear and tear.
When the VVT dance too much, it will hit its end walls, thus that knock-knock sound. Like in video below :

CaliBenzDriver

Thank you Master Surya for these outstanding datasets you grace us with.

Always on the pulse of things... with true examples.



INT spike... VVT overshoots its position BY A LONG SHOT to Maximum degree.


EXH spike... same overshoot in opposite direction

It looks like the VVT target position is pretty much the stable once actuated.



VVT target position is unchanged regardless of RPM!!!

Target timing camps on one spot from 1200 to 4000.RPM - VVT actuates and remains unchanged regardless of RPM.
I am beginning to wonder if VVT are not just to help engine crank easier due to a more favorable timing.


Any idea.... why the VVT ends up in the weed when engine crosses 3500.RPM.... oil pump shifts!

I bet these are old graphs are with MOD.0 "stock" oil Mgt, yes?

That's why I've said the pressure step switching from low to normal impacts VVT timing by corrupting the VVT map.


MOD1 cancels that issue to let ECU build worthy maps.


++++ WAIT THERE'S MORE .... up above idle:
Let's see how stock VVT activates upon leaving low idle, the oil pressure begins to rise ...


INT activation overshoots position

Based on what I can see stock reaches target position around 1200.RPM before overshooting past it and coming back.


EXH activation overshoots position

The ECU request Max PWM on the VVT solenoid to position it.

Then oil pressure shows up and overshoots position before it gets corrected through PWM.


What if we could get more oil pressure to activate VVT at lower RPM without any step near 3500.RPM ?? MOD1.0 no more messed up timings.

These wild VVT timing spikes can not be accommodated well by HPFP proportioning valve.

nika_kirkitadze

Thank you for your investigations CaliBenzDriver S-Prihadi

Most likely I should replace all intake and exhaust camshafts?

S-Prihadi

You must also replace the mechanical oil control solenoid and the magnetic solenoid ( can leak oil into wire harness ) which controls the mechanical solenoid..... aside from the 4 phasors/VVT sprocket.
Best all 4 camshaft position sensors ( can leak oil into wire harness ) replaced too.

150,000KM is a good enough service for VVT and even oxygen sensors and injectors.
So you done well.

Try to see what price you can get in Europe.





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You will need to open up your cylinder head cover and you will need special camshaft lock tool. Get China one is good enough. I got the one below
https://www.aliexpress.com/item/4001...21ef1802zzBzdz


The higher cost part is the injector special tools , 3 of them. 1 is the more expensive one at US$300 approx.
Your must buy all 6 injector seal kit.

Will continue.................................

S-Prihadi

Mercedes Fuel Injector Drift Tool Kit - Genuine Mercedes 278589011500 this one the more expensive one
https://www.mbpartsexpress.com/oem-p...t-278589011500





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The injector seal at the tip. Need special tool. Injector puller tool too.


Injector seal tip install tool
https://www.mboemparts.com/oem-parts...-w272589004300


Injector puller
https://www.mboemparts.com/oem-parts...-w278589003300


The injector seals kit

https://www.mbpartsexpress.com/oem-p...kit-1770720000





Same method and tool for your injectors







..................... and all other gasket/seals when you need to do this job. Like intake manifold 6 seals and etc etc.
You need to figure that out yourself.


Good luck

S-Prihadi

Cali,

Use your OpenPort Xentry and log your COLD start VVT please.
I need more data from friends for database collection on M276.9 3.5NA

After that, log the VVT again with warm engine and do the quick 4,200RPM rev up and hold it there 5 seconds.

Thank u

juanmor40

I am a bit confused here. I understand the VVT's are gone --> replacement is next.

However, why do we need to change camshafts? No need unless the cams are scored or flat, correct?

Why do we need to open the head covers at all? The VVTs come out w/o removing a single head cover, nor disturbing the injectors. Only the timing covers. It is supposed to be a front engine work alone.

S-Prihadi

Whose changing camshafts ?
I told Nika to replace CAMSHAFT POSITIONER aka VVT/phasor


Juan ask :
Why do we need to open the head covers at all? The VVTs come out w/o removing a single head cover, nor disturbing the injectors. Only the timing covers. It is supposed to be a front engine work alone.

Juan, only reckless guy will tighten or loosen the mechanical oil solenoid and the VVT/Phasor using timing chain as locking device.
One need to lock the camshaft with camshaft locker, otherwise the timing chain will take the tightening and loosening load.
Tightening load is 130Nm for the mechanical oil control valve, it the same as our wheel bolt.
See the WIS I attached.

You have to be careful when watching Youtube videos, some so called techie do not use camshaft locker to replace VVT/Phasor.

The correct way


The RECKLESS way. In China.


.
The correct way............ I had to buy the camshaft locker for my friend's M271




Extra.....

juanmor40

Thank you Surya. I am trying to understand the purpose of the tie-down cam tool. It seems to prevent sliding of the camshaft relative to each other, correct? It is not to hold the cam while torquing since that is done from the rear of the cam.

S-Prihadi

The 2 camshaft lock down bars for M276 does lock the camshaft tight. I guess MB wanted extra caution and request to use the Torx T60 at camshaft rear azz as back up.

On M271 no need extra hold down using the rear of the camshaft with a torx or any tool. Simply a single camshaft lock-down bar.

The M276.x camshaft itself has 2 claws as camshaft "keeper" at the engine itself.

S-Prihadi

Juan,
Come to think about it, maybe you are correct.
M271 camshaft lock-down bar is not round shape, it is like a fork. With a square kind of "U"



The M276 camshaft lock down tool is round and only gripping from top side, being only 1/2 round.



So perhaps it wont be as grippy as M271 camshaft lock-down tool.
Hence the T60 Torx is still required as the main "brake"

nika_kirkitadze

Did not managed to see values in Xentry, I think did not found proper instrument / tool in Xentry itself

So I removed sensor for bank 2 - intake and rev the engine manually (see video)

Video: https://drive.google.com/file/d/1WMC...ew?usp=sharing


My question here is if others are damaged as well do they slip at a same time all? Did not checked others yet and trying to figure out

nika_kirkitadze

For now I can share cold start video recording - record date is 2023-12-04

https://drive.google.com/file/d/1X-s...ew?usp=sharing

DeanMassy

By stretch in degrees highest at 1.36*, no need chain to be replaced yet. Once near 3 degrees, replace it.