VVT question (slightly technical)

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You're just taking a poke.

Ha! I learnt the hard way to always peek and never poke

[sweegie]

You're just taking a poke.

Ha! I learnt the hard way to always peek and never poke

And never fiddle with bits unless you know what they do

[Shoppinit]

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Hardcore.

[Shoppinit]

Call me a cab.

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You're a hairdresser's car.

[Shoppinit]

When I get some time, I'll trace back the measuring block parameter to an internal ECU variable & see where that takes me. Keep you posted

Bump

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Call me a cab.

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now call me an ambulance.

[sweegie]

Aah, yep, that's what I was supposed to do.... I've not traced this in the code yet, but I'm pretty certain you're looking at dwnwsp_w there. I'm too tired to paraphrase so here it is in all it's Bosch glory....

DNWKW 3.40 Diagnosis alignment between camshaft and crankshaft

The section %DNWKW discribes the diagnosis of the alignment between the camshaft/s and the crankshaft. Therefore the adapted
position of the first phase edge (see %WANWKW) is compaired with its nominal position.

dnwkw-dnwkw-nw1
Determination of the deviation of the camshaft position from the setpoint position:
-----------------------------------------------------------------------------------
dwnwsp_w = WNWSPS*_0 - wnwsp*_w(0)

adjusted to advanced: dwnwsp* w > 0
retarded: dwnwsp* w < 0

DWNWSP_W = Deviation of the adap. angle from engine-spec. setpoint angle of the camshaft
WNWSPS_0 = setangle of the edge 0 of the camshaft in the reference position
WNWSP_W = Adaptation angle of the camshaft in retarded end position

WNWSP_W is set in the WANWKW function:

FB WANWKW 13.30 Detailed description of function
Angle detection of alignment between crankshaft and camshaft
------------------------------------------------------------
In the case CMS interrupt, the angle wnwkwas* w is measured relative to the zero point in the working cycle (R syn & zzyl=0):
wnwkwas* w = (tooth in working cycle + tooth improvement) * SY WNBM
Release of the adaptation:
--------------------------
The adaptation is only released if the first gap check was successful (B bm=1), if a engine speed window is not exceeded,
if the engine is idling and no longer in the start range and if the engine speed and phase signals are error-free.
On systems with camshaft adjustment the adaptation is only released if it is sure that adjustment is in the retarded position
(B nw s) and that the diagnosis for camshaft adjustment has not detected the advanced position (B nwsvf*).
Each adaptation of the CMS position to the software reference mark wnwsp* w(i) is performed in the CMS interrupt (R ph*) providing
that the condition B spsa* is fulfilled: The difference to the current adaptation value is given by the deviation wnwi* ad w.
With, e.g., a positive wnwi* ad w, the current value wnwkwas* w is greater than the adaptation value wnwsp* w(i). The adaptation
then tracks wnwsp* w(i).

The adaptation angle wnwsp* w(i) is tracked via a low pass with the time constant ZNWSP and is limited by the limit values WNWASMX
and WNWAFMX with reference to the setpoint value WNWSPS*(i). The adaptation value wnwsp* w(i) is stored in the permanent RAM.
In the event of powerfail, the RAM-cells wnwsp* w(i) are loaded with the fixed values WNWSPS*(i).
The floating average value wnwim* w of the angle wnwi* ad w is used to determine whether the adaptation condition can be applied.
The adaptation status is stored in the condition B phad*:
B phad* = 1: Adaptation of the phase edge is being performed and is valid
B phad* = 0: Adaptation of the phase edge is not valid
The adaptation for the second camshaft is performed in the same way as for the first camshaft. The adaptation is performed
separately for both sides, i.e. two adaptation angles wnwsp w(i), wnwsp2 w(i) exist as well as, two deviations wnwi ad w, wnwi2 ad w
from these adaptation angles, two floating average values of the adaptation value wnwim w, wnwim2 w, and two resulting
conditions B phad, B phad2. The values wnwkwas w, wnwkwas2 w und wnwspas w, wnwspas2 w are also both available in this case.

[Shoppinit]

So it looks like the difference between the 2 different measuring block variables is that one is the the raw angle and the other is the angle after the adaptation value has been applied to it for the advanced or retarded condition. Kinda makes sense.

[sweegie]

Indeed. Crank angle is taken as the absolute truth, and cam angle is derived from the phase mis-alignment by comparing the measured trigger point with WNWSPS.

An error condition exists if the alignment exceeds the static constands WNWSPMX or WNWSPMN, set in the ecu flash. I have WNWSPMX = 16 and WNWSPMN = -20 so looks like there's quite a large tolerance for this measurement. Shame that it looks like its not suitable for measuring cam belts that have been swapped incorrectly.

Fault:
dwnwsp*_w > WNWSPMX: B_mxnwkw* = Camshaft position adjusted too advanced
dwnwsp*_w < WNWSPMN: B_mnnwkw* = Camshaft position adjusted too retarded
else: E_nwkw*=0 = Camshaft position is within the permissible range of tolerance

[Shoppinit]

We've still got the raw info of °CKS relative to °CMS though, no?

[sweegie]

Sure, but I'm not sure how accurate the measurements are - ie how well the cam timing marks are machined. Guess you could do a before and after on a cam belt swap, to make sure all was good though. The error condition only appears to cater for big alignment problems, such as a stuck de-phaser.