MoTeC Global Forum

I'm running a BWM M54 engine with VANOS. (Continually variable inlet and exhaust camshaft control)

The M1 uses a somewhat static feed forward control strategy, where a 1D table is used to set base duty cycle on the control solenoids based on oil temp.

This wouldn't be a problem if oil pressure was constant at all RPMs, but this isn't close to being the case with this engine:



As a result, I'm having a lot of trouble getting the camshaft to follow target position, regardless of PID settings. If I go more aggressive on the PID, it works at lower engine RPM, but goes into oscillation at higher engine RPMs. Changing the Feed Forward duty cycle at normal engine operating temp just causes the cam to follow target at different RPMs, but lose control at others.

It seems like the feed forward table needs to be 2D, with both engine speed and oil temp taken into account.....

Has anyone else had these issues?

Hello,
Can you send some logging of this please. It is a bit hard to tell what is going on from just a scatter plot. Generally the cam control is not relied on at very low engine RPM, some factory ECUs even turn it of until above idle to ensure plenty of oil pressure.

Sen me some logging (not screen shots) showing examples of what you are talking about.

I have just gone through the same setup with an M800.

I have found that the oil temp doesn't have much affect. I used rpm as the input to the cam duty correction table as what is done in the factory MS43 ECU.

Of course oil pressure would be better but the factory setup runs a low pressure switch which I have not changed from.

Did this get resolved? How? Inquiring minds want to know!

--Peter

Herrubermensch wrote:Did this get resolved? How? Inquiring minds want to know!

--Peter

Peter,

Yes, Mark McCoy @ Motec worked with me via email to help sort it out.

My biggest issue was that I didn't have the feed forward gain setup properly.

If anyone is starting this process from scratch, I highly recommend High Performance Academy's Motec M1 course which gives a step by step explanation of how to setup variable camshaft control.

https://www.hpacademy.com/courses/motec ... -tutorial/


Once I had the feed forward at a point for each camshaft where it would hold the position steady, I started increasing the PIDs under running conditions to try to stabilize the actual position vs target position. On the exhaust VANOS I ended up at 35% DC, and on the inlet VANOS it was 75%.

Note: the inlet VANOS uses "inverting" on the signal so the DC goes down to move the camshaft position from resting.

A cautionary note: I switched the exhaust camshaft control from "normal" to "inverting" with the engine running and the resulting instantaneous force on the VANOS caused it to break the control spline on the camshaft. I had to tear into the top end of the engine to fix what was effectively a tuning error...

PEI330Ci wrote:

Herrubermensch wrote:Did this get resolved? How? Inquiring minds want to know!

--Peter

Peter,

Yes, Mark McCoy @ Motec worked with me via email to help sort it out.

My biggest issue was that I didn't have the feed forward gain setup properly.

If anyone is starting this process from scratch, I highly recommend High Performance Academy's Motec M1 course which gives a step by step explanation of how to setup variable camshaft control.

https://www.hpacademy.com/courses/motec ... -tutorial/


Once I had the feed forward at a point for each camshaft where it would hold the position steady, I started increasing the PIDs under running conditions to try to stabilize the actual position vs target position. On the exhaust VANOS I ended up at 35% DC, and on the inlet VANOS it was 75%.

Note: the inlet VANOS uses "inverting" on the signal so the DC goes down to move the camshaft position from resting.

A cautionary note: I switched the exhaust camshaft control from "normal" to "inverting" with the engine running and the resulting instantaneous force on the VANOS caused it to break the control spline on the camshaft. I had to tear into the top end of the engine to fix what was effectively a tuning error...

Wow, Adam, thank you! Excellent help!

--Peter

PEI330Ci wrote:

Herrubermensch wrote:Did this get resolved? How? Inquiring minds want to know!

--Peter

Peter,

Yes, Mark McCoy @ Motec worked with me via email to help sort it out.

My biggest issue was that I didn't have the feed forward gain setup properly.

If anyone is starting this process from scratch, I highly recommend High Performance Academy's Motec M1 course which gives a step by step explanation of how to setup variable camshaft control.

https://www.hpacademy.com/courses/motec ... -tutorial/


Once I had the feed forward at a point for each camshaft where it would hold the position steady, I started increasing the PIDs under running conditions to try to stabilize the actual position vs target position. On the exhaust VANOS I ended up at 35% DC, and on the inlet VANOS it was 75%.

Note: the inlet VANOS uses "inverting" on the signal so the DC goes down to move the camshaft position from resting.

A cautionary note: I switched the exhaust camshaft control from "normal" to "inverting" with the engine running and the resulting instantaneous force on the VANOS caused it to break the control spline on the camshaft. I had to tear into the top end of the engine to fix what was effectively a tuning error...

Adam,

Are the settings you and Mark came up with based on the Schrick cams or stock?

If either - would you be willing to share the Cam Control for both the Inlet and Exhaust to close the loop on this post?

I'm getting ready to make the transition from the S52B32 to an M54B30 and find this very interesting...

Thank you!

-

Trever

Trever,

Are you running a turbo or N/A engine?

Hi Adam,

Sticking to N/A for now.

I've started down this path with my current engine to get a better understanding...

Thank you!