VVT test duty backwards on retard?

[CSXRT4]

Im testing VVT outputs on the jimstim using the VVT test mode. When the cam is set to "more duty means advance" the output corresponds correctly with the commanded test duty. But when set to "more duty means retard" it seems to be inverted (100% commanded duty actually gives me 0% output duty).

Is this a bug or am I doing something wrong?



Pic for reference.

[CSXRT4]

Bump

[CSXRT4]

Any input?

[CSXRT4]

Hoping to get this figured out before we get the engine fired up. This must be a bug or something, I don't see why output duty would need to be inverted to commanded duty?


This testing was done on the ms3 beta10

[Matt Cramer]

[CSXRT4]

Its really all in the VVT table but here is an MSQ. The attached msq is just the default supplied 1.4 beta10 msq with dual wheel enabled and VVT settings configured.

This is easy to test on the stim. Just set up an msq for VVT (or use my attached one), then set the stim to 36-1 and get the RPMs going (not sure if necessary). Set one of the cams up to output on injector1 or 2 and set "more duty = advance". Turn on the cam test mode for that cam, set the duty to 0% and then burn all of these changes and power cycle. The injector led you specified for an output should be off, now change "more duty = retard" and burn/power cycle and the injector led will turn on even though you are still at 0% test duty. Now with it set as "more duty = retard" you can set the test mode duty cycle to 100% and hit burn and the led will turn off. Completely inverse behavior as to "more duty = advance".

Setting the cam as an intake or exhaust cam doesn't seem to have an effect on this issue.



Thanks

Jason

[muythaibxr]

The feature is working as intended. The PID routine requires low duties to retard and high duties to advance. So rather than translate the number from PID to something else, the output is inverted when needed.

This is working as intended.

[CSXRT4]

So in my case where I need more actual output duty to retard my exhaust cam then should I set it to "more duty = advance" and then set it to "table is retard"??


It seems like there should be a note somewhere that output duty will be inverted when set to "more duty = retard". Maybe other engines are different but subaru has its intake cams rest at a retarded state and advances them as you add duty to the solenoid, exhaust cams rest at an advanced state and retards them as you add duty to the solenoid.


I think im misunderstanding the system because maybe its designed for use on an engine ..cough VANOS cough.. that uses a different control scheme? Between the output inversion and "hold duty" I get the idea that other systems cams might sit at a neutral state at say 50% duty and then advance and retard from that point with more or less duty?

Jason

[muythaibxr]

So in my case where I need more actual output duty to retard my exhaust cam then should I set it to "more duty = advance" and then set it to "table is retard"??

No, that seems backwards

I think im misunderstanding the system because maybe its designed for use on an engine ..cough VANOS cough.. that uses a different control scheme? Between the output inversion and "hold duty" I get the idea that other systems cams might sit at a neutral state at say 50% duty and then advance and retard from that point with more or less duty?

It was designed for systems that require 50% duty (or some other duty) to hold a position.

However, there is no reason why it shouldn't work with other types of systems. Hold duty should be optional. It is my understanding that most VVT systems work this way though... Toyota and Mazda do at least.

Ken

[CSXRT4]

What configuration would I need to set up so that more actual output duty will retard my exhaust cam and as actual ouput duty decreases to 0% the exhaust cam will return to its fully advanced rest position. Along with the PID system correctly adjusting the duty in closed loop so as to increase actual output duty to further retard the cam and decrease actual output duty to advance the exhaust cam (although its not really "advancing" but rather reducing the amount of retard).

My engine is exhaust cam 0% duty = full advanced "rest" and 100% duty = full retarded.

[jsmcortina]

I loaded your MSQ and it is configured to control 4 intake cams?

The configuration needs to have the VVT channels set for the intake and exhaust cams.

The "Table is advance/retard" will normally be set to "Retard" for exhaust cams.

The "More duty means" setting should be set so the cam moves in the expected direction.

James