Vanos Rebuild Start Hesitation

[jamesfoley]

On the graph you posted I see the cold start ex cam issue as I posted earlier: expected 15 degrees but actual is only 3, for a short duration but enough to be different than warm starting.

Both cold and warm start seem to be around the same, if you look at the Google Sheets spreadsheet of the values from that graph pretty sure line 8467 is where the engine is turned off with actual being set to 0 but expected being set to -10. Then line 9268 is warm start where actual is now -4.2 and expected is 9.5. Cold start has an actual of -1 and an expected of 12, you can see from my other cold start logs further up that I've also has -5 actual, 11 expected.

The numbers feel weird but can't tell if its normal or not. I figured there would have been a VANOS tables somewhere in the DME.

[sapote]

Not sure I understand what you mean. I was just saying that the exhaust actual and expected deviation is the same both cold and warm start.

Do you mean the exhaust cam expected should hold 12 degrees for longer than it does?

Is

On the graph you posted I see the cold start ex cam issue as I posted earlier: expected 15 degrees but actual is only 3, for a short duration but enough to be different than warm starting.

[jamesfoley]

Not the same: expected should be 12 degrees for some time but actually only get to 3 degrees

Not sure I understand what you mean. I was just saying that the exhaust actual and expected deviation is the same both cold and warm start.

Do you mean the exhaust cam expected should hold 12 degrees for longer than it does?

Is it possible to cross reference these values with a table from the MSS54 XDF?

I've tried checking the partial I pulled from my DME using TunerPro and the 1301 XDF, though a lot of the data is just jumbled so assumed there is something up with the 1301 XDF

[sapote]

Only because of the Y axis scale, the actual values are the same.

Not the same: expected should be 12 degrees for some time but actually only get to 3 degrees

[jamesfoley]

Cold start graph shows totally different than warm start

Only because of the Y axis scale, the actual values are the same.

[sapote]

Scales for the graphs are different, exhaust cam actual is -1 degree when expected is 12 degrees for some reason. They then align to 3 degrees, +/- a degree.

However the same discrepancy is there when the car starts normally, so I don’t know if it’s actually a problem, or if the car just starts easier when warm even with this cam position difference on the exhaust.

VANOS test proves there is nothing wrong with the timing as it reaches the expected positions without an issue.

Don’t know if perhaps my exhaust cam position sensor is just doing a shit job at reading the cam on engine start, though if it was the sensor I’d expect drivability issues somewhere.

Also don’t know if that’s just how the DME works for the version I have.

Cold start graph shows totally different than warm start.
Vanos test was done with warm engine and so it’s fine.
if the cam sensor is glitchy then you would have error codes

[jamesfoley]

Cold start ex vanos issue:
The ex expected is 3 degrees retard but the actual shows 50 retard. So the ex couldn’t advance from max retarded to 3 degrees retarded.

Scales for the graphs are different, exhaust cam actual is -1 degree when expected is 12 degrees for some reason. They then align to 3 degrees, +/- a degree.

However the same discrepancy is there when the car starts normally, so I don’t know if it’s actually a problem, or if the car just starts easier when warm even with this cam position difference on the exhaust.

VANOS test proves there is nothing wrong with the timing as it reaches the expected positions without an issue.

Don’t know if perhaps my exhaust cam position sensor is just doing a shit job at reading the cam on engine start, though if it was the sensor I’d expect drivability issues somewhere.

Also don’t know if that’s just how the DME works for the version I have.

[sapote]

Cold start ex vanos issue:
The ex expected is 3 degrees retard but the actual shows 50 retard. So the ex couldn’t advance from max retarded to 3 degrees retarded.

[jamesfoley]

Just a small update with some data I have.

Results of VANOS test, and adaptations taken with DIS:


Cold start with hesitation, graph of VANOS intake and exhaust actual and DME expected positions:


Warm car running, key off and then engine start again, car did not hesitate this time but still has weird 10 degree jump on the exhaust positions:


I also have a VANOS cam position log which was started just after the cold start graph. It seems that both cams do stick to the DME requested position with a degree or two of difference, so I think its working as expected.

There are a couple of rows I've highlighted in orange though where there is a 10 degree difference in the exhaust cam actual and expected, seems to be at engine stop and start.

https://docs.google.com/spreadsheets/d/1u9PBg3NKFgR7Bph15trebvIxyyKTSn6TYibcxIgrvok/edit?usp=sharing

The car did run super rough while it was testing the exhaust side of the VANOS which I'm assuming is expected as its fully advancing and retarding the cam?

[jamesfoley]

In 3 videos I see engine ran normal. The M3 doesn’t start up smoothly as non-M cars.

My previous M3 never did this, and this never happened before I had the VANOS done, so to me it doesn’t feel like it’s a normal thing…

[sapote]

In 3 videos I see engine ran normal. The M3 doesn’t start up smoothly as non-M cars.

[jamesfoley]

First start after the car sat for a week while I was on holiday, hesitatesas the engine was trying to catch while cranking and then runs fine.

[jamesfoley]

Here is a good one, roughly 3 hours after the video in my above post. Hesitation at start and ran rough until RPM settled just under 1k:

[jamesfoley]

Got TestO working graphing both bank 1 intake and exhaust camshaft actual positions and DME expected positions.

I have no idea what the exhaust cam is doing when it fires up, but thats where the hesitation I feel is. This is a smaller hesitation than usual, but logging every engine start with my laptop is a ball ache. Video is of the same start, doesn't really come across well but it can be felt and heard in the car, this one being one of its better starts so hesitation is short.

Car hasn't been used for around 2 days before this start, so cold engine.

I'm assuming TestO reporting values for bank 2 is normal? With only 1 intake and 1 exhaust sensor, not sure where the exhaust bank 2 actual value is coming from in that left hand side table.

[sapote]

I see what you mean but I think that’s just where the front of the VANOS body is not the same as the front of the piston. Back side of the piston is generally the side with the larger surface area that pushes the piston outward, regardless of orientation.

On the car, the best way for everyone to agree is to use the car body when referring to left right front and rear sides.

Part orientation should be referenced the same way.