S-Prihadi

I'll be darned.............

If I have I trusted my Xentry Passthru with even a genuine Tatric Openport 2.0 to log camshaft dynamic value for troubleshooting VVT response speed, I could have been chasing my own tail.


Xentry Passthru. I think the update speed is only 1 data point per second or 1 HZ. BELOW : I was having fun with it back in Dec 2021 Bali.

Above data of Dec 2021 have always baffled me, because I know it lacks resolution and if I am not careful it may seemingly indicated ECM command not properly
executed by the VVT sprocket or oil phasor or a drifting camshaft position sensor
Autel is also slow, 1HZ maximum but it does not have the complete camshaft diagnostic menu field like Xentry above, so I could never verify this, till today.



BELOW : BenzNinja System 7.43 data points per second. Finally I can see use-able data for the camshaft overall VVT responds to ECM command(set-point/specified) and the proper reading of the camshaft sensor (actual value ).
No more missing data points.





DATA DENSITY COMPARISON

I think my Xentryt Passthru Kit is not even a true 1HZ, would be less like 0.75HZ maybe ............. if seeing above archive.. The green line seems to have weird data. I did not have the CSV file for the Dec 2021 capture.



The data resolution is so worth it this BenzNinja C4 system
I wonder if this 7.43HZ is limited data transfer between car computers towards C4 multiplexer or it is indeed the speed of the VVT command ?
I know ABS pulse command is a super fast one.



Data below is what I been thinking for a long time. How fast can ECM respond to a dynamic RPM increase of 4,000ish per second and smooth out the data and not screw up the advance/retard accuracy.
The electronic is no issue for such a slow 7.43 HZ speed, the hydraulic part of the phasor sprocket oil pressure management is what I been curious about as the oil inside the VVT sprocket has spinning inertia from the camshaft.
I think there is some prediction algorithm involved too when RPM rate of rise per second is high.



Quite amazing, data line 306 ECM commanded 28.73 degrees advance to right bank inlet VVT and actual VVT was still lagging at 15.84 degrees or 12.89 degrees short. Time at 41,784 milliseconds.
By 41,915 milliseconds or 131 milliseconds later , ECM commanded 33 degrees and the VVT managed to be at 31.35 degrees, short only by 1.65 degrees.
By 42,035 milliseconds or another 120 ms, ECM commanded still a 33 degrees, VVT goes to 32.71 degrees and short of only 0.29 degrees.
1/4 of a second all it took and this is hydraulic action.



BELOW : How the hell the VVT system can maintain oil pressure to get 33 degrees only, when maximum movement is 36 degrees.
I mean the system only has B holes, 2 of them as means to adjust advance degree and it does not overshoot to 36 degrees which is only 3 degrees away or few millimeters only.
No wonder they don't last very very long, +4 degrees drift and that's it ..........the famous knocking sound will occur. Dynamic VVT is indeed cool and high accuracy.







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



The original file produced by the Xentry-Ninja for the camshaft is a CSV. Maximum recording time is 120 seconds or 871 data points. In German language, I color the word in green.
Yellow highlight is translation by Google. Top most field is my own description for the data field.


Below is a cold start about 12 seconds after engine fired up, hence RPM at 900ish.
I am curious column B and C, I know it is milliseconds value and it is about Intake(B column) and Exhaust ( C column )....but what does it actually means ?











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





I am looking at my Bank 1 ( right side ) EXHAUST VVT system being 2 degrees over target, I do not know if it is the sprocket or oil control valve or the phasor magnet pin travel is the culprit.
Or the chain ?
Or the camshaft sensor ?
Commanded -23 degrees, actual -25 degrees.
Well, that is for another day to think about.


That is all for today.................

BenzNinja

iTrader: (4)

thank you !

DFWdude

Sorry, but I fell asleep after the second chart...

ghlkal

Interesting stuff, as always, S-Prihadi

Where did you get the image of the "Camshaft adjustment, function"? I would love to have a manual that explains how our engines operate.

S-Prihadi

I know those excel files made me sleepy too

S-Prihadi

Here attached.
Specific to 3.0 Turbo, that booklet from MB has wrong timing data. I attached the correct one too. Enjoy.

S-Prihadi

NOTE :
The information below and split 1/2 way by MB is because it is showing 2 conditions, FULL RETARD and FULL ADVANCE at the same time, which is not possible. Hence there is a thin line separating half of the camshaft sprocket is drawn.



Intake VVT and Exhaust VVT is different only because one is mainly for RETARD and the other mainly for ADVANCE.
So their lock pin position is different and their direction of movement is different.

Above in cyan is where the lock pin location is for Intake (Left of image ) and Exhaust (Right of image)

Image above from here :

S-Prihadi

Little digging of my Exhaust RIGHT VVT on Bank 1 being 2 degrees off.


At cold start, VVT can achieve the degree of retard as commanded by ECM, -5 degree and RPM 900 ish.
Later when RPM is brought down to 700 ish, the VVT does -25 degree where the ECM was commanding -23 degree. This idling speed of 700 to 600 sh RPM is where the 2 degrees drift started.
This 2 degrees drift is not happening at Exhaust LEFT Bank 2

Data point above at 7.43HZ


When I do revving up ( car stationary ) to 3,500ish RPM, the Exhaust Right Bank 1 is OK, it can follow ECM command.
Overshoot a bit is normal for such fast and sudden rev up.


Above based on time, shows the red as a software command and blue line as a result of that command by a hydraulic VVT. There will be lag for sure when at high RPM.
This Ninja-C4 is paying for itself by a mere 7.43Hz data capture resolution Without a scope I am now able to see many fast data points.
If this C4 can do 20Hz , I will smile ear to ear


The revving up is from the session below:







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



Its just so weird. During idling, that is the EASIEST condition for VVT to meet ECM position command....and yet it went drunk by 2 degrees
During hard fast revving up, is the most difficult conditions to achieve for VVT and yet it can do it well.

I will look into camshaft re-learn/RESET feature, I hope it is available in the Xentry as part of the correlation to crankshaft.

Above is how the ECM keep reading wear and tear on the timing system and make adjustment/compensation dynamically when needed, but only up to a point. I think 5 degrees off is maximum.
One flywheel tooth is worth 5 degrees on M276 and I believe most modern MB will use this high resolution 60 tooth (58 + 2 empty ) flywheel.


.

S-Prihadi

Looks like I found the most likely reason for the 2 degree OFF/DRIFT of Exhaust VVT Bank 1 ( Right )/
Needed to use my scope to measure physical placement of camshaft or rather its signal tone* wheel ( *reluctor wheel ), which it can spin out of place too...yikes !!! Mine did not spun out of place, I don't think so.









I seen this issue at Pine Hollow Auto Diagnostic channel. Tone wheel spun by a good 5+ degrees and caused timing error computer calculation wise.
I don't understand why NOT OE uses 2 small micro weld to keep this tone wheel in place ?


Compression fit only for a spinning disc carrying God knows how many Gs of force at 3,000 camshaft RPM ( 6,000 crankshaft rpm )



It seems my 2 degree error/DRIFT is from the 1st day of MB Indonesia adaptation when the CKD assembly completed.
The camshaft adaptation is not so straight forward.






I have not done any adaptation yet.
However this M276 camshaft adaptation is not so troublesome like below video, the MB engine model of W203 C230 : Start at 25:30



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

Anyhow here is the physical camshaft position as seen from its signal tone wheel by a scope.








BELOW : Intake VVT


SEE magentic phasor DUTY CYLE at 90ish% at idle. Above image.






Tone wheel hill and valley and the signal output - IDLING RPM - Intake VVT







At 4,180ish RPM, the Exhaust VVTs do match up closely between LEFT and RIGHT bank, hence they were always within commanded degrees of ECM at high RPM. So Xentry raw reading is correct.






So Xentry showed the true raw reading of camshaft position sensor, it is the ECM which will do the compensation/adaptation from its memory.


I also measured the duty cycle of the magnetic phasor. It is a push type solenoid. So that means the oil control valve is a normally closed one until it get pushed by phasor needle/rod, because at idling the duty cycle is 95+% and at 4,000ish RPM its 55-60% duty cycle ( less push to oil control valve ).





The Right side ( Bank 1 ) exhaust cam position sensor is not so easy to undo its screw, turbo vacuum actuator and coolant bottle in the way. I also have swapped between LEFT and RIGHT bank the Exhaust pos sensor to eliminate sensor issue.








Avoiding cable getting to serpentine belt




Left laptop is Xentry-Ninja , right is Pico. Its really nice to separate both of these software on different laptop




My DIY signal intercept wire kit is useful




I shall report back when I am able to do a proper camshaft re-learn/adaptation.