350Z VQ35DE Cam Control on M800

[Alex B]

Hi Everyone,

Having trouble getting cam control to work on VQ35DE with M800 wired as
piggy back controlling ignition, fuel, DBW and cams.

Cam position sensors wired to DIG1 and 2 inputs. Cam solenoids wired
to Aux 3 and 4 with flyback diodes. Everything setup and cam pos. sensors
zeroed with connectors off solenoids putting any number other then 0
moves right cam to max advance 40 degrees while left doesn't move at all.

Checked power supply to the solenoids. Its fine and is from stock source.
Tried using different diodes and other outputs made no difference.
Shorting the Aux outputs to ground does move left cam and advances
right to the max right away.

Also once engine starts right inlet cam duty goes from 25 to 0
while cam is going from 0 to 40.

When wired to stock ECU cams stay at 0 with slight
retarding on acceleration.

Cam position and control settings are below.

Any ideas?

Thank you in advance.

Best regards
Alex

[Ben-S]

My first question would be what are you using to sync the engine if you are using dig 1 and 2 for cam control.

I don't use any diodes in my setup.

Have you set the normal position under the function->cam control menu?

Have you checked to make sure you do not have the aux outs and dig inputs swapped (for example you are using the left cam sensor to control the right cam). Have you checked the wiring from the ecu by pin number (and with a multi meter). There is at least one manual floating around the internet for 03 350z's with a few wrong wire colors (at least) at the ecu connector which caused me quite a bit of trouble when I first installed an M800 in our shop car. Maybe just a really early model 03 since that was the first year but its worth double checking.

[Martin]

I dont think you high and low limit is correct. Ive got the high limit on a DE at 85. (Not a stock engine though)

My Pgain is also lower, but thats not the problem you are having. Ive found that on some engines the 2 cams run at different DC`s to keep the same position.

If you have set the Actuator normal position you will have a small + and - values in the Hi and Low Limit values.

[Alex B]

Ben-S
For engine sync I use LH cam pos. sensor wired to Sync input on the ecu and DIG1.

What is the function of these diodes? I was advised that to use cam control on Aux
3 & 4 flyback diodes are required.

All wiring is checked with the multimeter. All is correct.

Martin

I did swap in another M800 with the latest 3.5M firmware, converted the car setup
file from 3.32E and was really surprised when I saw cams started to work! Doing some
tweaking with the control parameters reduced P to 2.0. Still however large duty cycle
were required to move the cams so tried changing the frequency from 300 to 200,
100, 50 and 20 and found that 20 gives duty cycle within 30-60%. Left it at this for now.
Finally set normal position table and changed hi & low limits to +/-10. Tried running
with and without diodes wired didn't make any difference.

One thing that needs further investigation is cam pos. noise on engine acceleration
or deceleration. Not sure why its doing, no ideas at the moment. At least internal
scope reads cam & ref perfectly.

Probably the old M800 I used initially needs examination of its internals.

Best regards
Alex

[Ben-S]

The purpose of a flyback diode is used to keep from having a high energy spark across opening contacts in relay's h-bridge drivers, or basically anything with a coil and mechanically switched contacts. I did not think you needed to add one to the circuit although I am using aux 5 and 6 which are slightly different internally although I do not know the specs or anywhere to look them up. I do not have those diodes and have not had a problem (yet).

I also have 80 as a maximum position but that doesn't seem to be your problem and I have some pretty large cams and heavy springs which I would imagine require greater duty though to be honest I do not know the inner workings of this particular variable cam setup.

I use 300hz for my frequency so I'm surprised you have gone so low

You do not need to have the cam position sensor wired in twice, you can use the sync sensor for cam position measurement, I do not know if having it replicated could cause control issues maybe someone from MoTeC can chime in. You are basically just wasting a dig input as you have it setup now.

[Martin]

I Use 200Hz

Remember, If you set a normal position table both cams will use that one table as the normal position.

You can wire it in twice, wouldnt make a difference. You are just wasting a digital. For the Sync to do cam position measurement you will need a ref/sync mode that will allow ref/sync measurement. So motec writes the mode for you to be able to do cam pos measurement on the VQ35 without the need to take the sync to a digital as well.

Not sure why 3.32 didnt work....

[Alex B]

Hi Martin, Ben-S,

Latest update.
Moved the cam control to Aux 5 & 6. Removed the diodes.
Also disconnected the LH cam sensor from DIG1 input and configured Sync Cam Position.
Immediately noted stable cam position reading on both cams and more stable engine
running. Probably parallel wiring to Sync and Dig input was casing it. Before that
engine would stumble occasionally while idling. After further messing with parameters
set freq to 200, normal position to 20 when 0 advance and 45 when 30 deg advance.
Cam duty varies from 15 to 55 and is similar on both cams.

Once more thank you all for your input.

Best regards
Alex

[MarkMc]

Set both cam outputs to just Function 3 for a duty cycle output table. Set the axes both to "off" so that you have just one value in the table. The frequency should be about 200.

Hold the engine at about 1300RPM to make sure you have enough oil pressure to run the cams. With the duty at 0% you should have both cams at a 0 reading (actually should be -1 so that when you ask for 0 in the table you cannot get any integral wind up).

keep adding duty cycle to the single table value until the cam starts to move. Use the page up/down buttons to find the duty cycle which makes the cam hold one position (not on either mechanical stop), lets pick 10-15 as a point to aim for.

The duty cycle that holds a cam position is the Normal Position. Set the Hi and Lo Limits at about this duty cycle -10 (lo) and this value +10 (hi). The normal position is assumed to be half way between.

TURN OFF all values and tables under Functions Cam Control, these are used for different situations and are unnecessary for the VQ35 and will confuse things.

The Hi and Lo limit if set incorrectly will really screw up the cam control and are the second things set after the cam position Offset.

[Alex B]

Hi Mark,

Thank you for the reply.

The duty cycle that holds a cam position is the Normal Position. Set the Hi and Lo Limits at about this duty cycle -10 (lo) and this value +10 (hi). The normal position is assumed to be half way between.

>> If I got it right, after we find the normal position we switch the Aux function to 117 cam control 1, right ?

TURN OFF all values and tables under Functions Cam Control, these are used for different situations and are unnecessary for the VQ35 and will confuse things.

>> Ok. What are these used for?

The Hi and Lo limit if set incorrectly will really screw up the cam control and are the second things set after the cam position Offset.

>> Understood.

Best regards
Alex

[MarkMc]

Hi Alex,
Yes once you have the normal position from your Function 3 test you turn the output back to the cam control, do the +10/-10 for the Hi and Lo Limits and start tuning your PID. Actually the +/- should be about 5 to avoid integral wind up but you need to be pretty accureate with your normal position.

The seperate Cam Control functions we for systems that were non-linear in their response to the PID so you could use the Duty Cycle Correction table to fix their response. Realistically I have not ever have to use it and it requires a fair bit of R and D to make it worthwhile.