Virtual Aux: Boolean Map

[krohelm]

Request:

Add at least one of the following features to PCLink and make available to the Monsoon ECU:

• An optional Table on the CAM-Switched function.
• A Virtual Aux boolean (on/off true/false) table.

 

Example use case:

Based on logged VE tuning with Toyota VVT ON or OFF, about 3.5 hrs of driving show maximum VE would be chosen as follows for RPM/TPS on my engine:

	2250	2500	2750	3000	3500	4000	4500	5000	5500	6000	6500	7000	7500	8000
10	1	1	0	0	0	0	0	0	1	1	1	1	1	1
15	1	1	1	0	0	0	0	0	1	1	1	1	1	1
20	1	1	1	0	0	0	0	0	1	1	1	1	1	1
25	1	1	1	1	0	0	0	0	1	1	1	1	1	1
30	1	1	1	1	1	0	0	1	1	1	1	1	1	1
35	1	1	1	1	1	0	0	1	1	1	1	1	1	1
40	1	1	1	1	1	0	0	1	1	1	1	1	1	1
45	1	1	1	1	1	1	0	1	1	1	1	1	1	1
50	1	1	1	1	1	1	1	1	1	1	1	1	1	1
60	1	1	1	1	1	1	1	1	1	1	1	1	1	1
70	1	1	1	1	1	1	1	1	1	1	1	1	1	0
80	1	1	1	1	1	1	1	1	1	1	1	1	1	0
90	1	1	1	1	1	1	1	1	1	1	1	1	1	0
100	0	0	1	1	1	1	1	1	1	1	1	1	0	0

Alternatives considered:

• Boolean conditions.
  - There are simply not enough conditions available between the aux output itself and all virtual aux channels to achieve the example.
• GP PWM output.
  - This is a hack; using a PWM output's table to switch 0/100% duty across 1 rpm.  It works for a proof of concept and shows the ECU is physically capable of this functionality.
• Using simple TP/RPM rule to define "rectangular" space for VVT.
  - That mid-range is where my car sits on the local high speed highways.  The rectangle rule ignores the OFF area and approximates a poor compromise.  The VE difference in many of the cells is greater than 10%.

 

[Adamw]

I havent seen this one requested before and I dont foresee many other uses for it so its unlikely to go much further unless there is more demand.  I dont see any problem with using a PWM table.

 

[krohelm]

How about wheelspeed/rpm for an electric exhaust branch?

Throttle position/rpm/gear to a shift light?  With close ratios and an engine with hp drop before redline there's a correct point at which to shift that differs by the gear ratio spread.

This person's use case http://forums.linkecu.com/index.php?/topic/6653-user-configurable-maps/?  (more complex but more general)

The lack of a map which provides a condition to other outputs crucially limits the utility of Virtual Aux.  In the example case, luckily it can be worked around by abusing a PWM output rather than using the correct CAM-Switched output.  I am not the most creative tuner out there, but surely there are a lot of uses for this!  

[Adamw]

How about wheelspeed/rpm for an electric exhaust branch?

I cant see why you just couldnt use std aux conditions for this, I dont think it would typically need to be 3D table based..

 

Throttle position/rpm/gear to a shift light?  With close ratios and an engine with hp drop before redline there's a correct point at which to shift that differs by the gear ratio spread.

 

We already have a gear based shift light function. Im not sure why you would need TP as an input for a shift light.

 

This person's use case http://forums.linkecu.com/index.php?/topic/6653-user-configurable-maps/?  (more complex but more general)

 This is different, I think he wants 4D/5D overlays added to other table based aux functions.  This has been requested many times and we do see its merits so it is already on the todo list. 

 

 

The lack of a map which provides a condition to other outputs crucially limits the utility of Virtual Aux.  In the example case, luckily it can be worked around by abusing a PWM output rather than using the correct CAM-Switched output.  I am not the most creative tuner out there, but surely there are a lot of uses for this!  

 The problem is adding functions like this even when they are turned off burn up memory allocations.  So unless it is a reoccurring request we are reluctant to add more "junk" in to the firmware to do a function that can already be done using existing functions.  If after some time we see this thread bumped up to the top regularly we will take notice and look at it again. 

 

[Ducie54]

I think your over complicating things. Put it on a dyno, do a run with it off and a run with it on. Where the power lines cross is your switch point.  

[krohelm]

I think your over complicating things. Put it on a dyno, do a run with it off and a run with it on. Where the power lines cross is your switch point. 

Thanks for your input:  Check the table, I measured VE off and on over a wide range of throttle and rpm conditions.  The correct setting for VVT varies by both throttle position and rpm based on logs composed of many thousands of data points.  This is not a 0-60 concern (simple rule > 80% throttle), but a drivability & efficiency concern (best highway setting needs 3d map according to data).

I'll be using the pwm table for now, and will refine it on a dyno.  Engines are complex, this is exactly as complicated as the data indicates.  Anyway, this is a wishlist request, not a tuning help request; I've demonstrated a feature need, now we wait for others to corroborate.

[CamB]

Question relating to using PWM being a hack. Is there any difference electronically (I mean from the ECU's perspective) between 100% duty cycle PWM and simply switched on?

[Adamw]

Question relating to using PWM being a hack. Is there any difference electronically (I mean from the ECU's perspective) between 100% duty cycle PWM and simply switched on?

Correct, there is no difference when at 100%.  Obviously also 0% DC is the same as an aux turned off.  

But what I think Krohelm is worried about in this case (understandably) is the in-between numbers 1-99% that you will get due to interpolation when transitioning from a 1% cell to a 100% cell.

As another user pointed out the workaround for this is to use a fine resolution or break points on the axis' at the transition areas so that the "switch" period is as short as possible. 

[krohelm]

Just for visibility in case someone else is tempted to do this, TPS is not a great axis to use with this strategy, as the tables hold 1% granularity while the runtime value is in 0.1% increments.  I manually verified on my on/off solenoid that it receives varied PWM in 0.1% increments while the throttle position is between 1% thresholds:  It interpolates in 0.1% increments, which can be a real problem for a solenoid that requires DC.  GP PWM is useful, but beware mixed granularity in both axes if using it for boolean logic!  There are other runtime parameters that will work fine for this, though, if you don't need TPS, or if your TPS spends most of its time at 0 or 100, though you probably wouldn't care about this anyway if so.

This most likely disqualifies GP PWM for the example use case, given that it requires TPS & RPM, and cannot tolerate PWM to the switch.