ACIS Tuning

Hello folks.

I have 22 Manual Transmission and I have been chasing for a while behaviors that feel like random misfires when accelerating throughout the RPM band. To my surprise, disconnecting the ACIS valve solves all the problems and the engine feels super smooth, however as expected, you lose a considerable amount of top end power.

So my next step was to open VFTuner and I moved the ACIS activation to 4500rpm, just to see what happened. After doing this and reconnecting ACIS the truck felt like crap again.

What I found is that the truck still plays with the ACIS valve UNDER 4500rpm or whatever the cut is set in the ECU. See the attached image and you will see the truck closes the ACIS valve under load but when releasing the throttle it opens it to the high rpm position, and never forces it shut until you press on the throttle again hard, and that is exactly when the "misfire like" situation is felt. So the sequence of events (this is my personal theory) is the following:

1. Driver accelerates from low rpm
2. At some point, the ECU forces the ACIS to the low rpm position
3. Driver releases throttle
4. ECU forces ACIS to the high rpm position, but never forces it back to the low rpm position
5. Driver waits until rpm drops
6. Driver presses on the throttle
7. The ECU realizes rpm are low and forces ACIS to low rpm
8. Driver feels a momentary drop in torque delivery while ACIS transitions

So what now? In VFTuner there is what I think a bit map to enable or disable ACIS features. I have tried to search the web for an explanation on how this works but I have not been able to find anything.

Hopefully one of those bits can disable the ACIS transition to high rpm when throttle is depressed.

 

You'd likely be better served posting this in the Performance and Tuning forum: https://www.tacomaworld.com/forums/performance-and-tuning.8/

 

There are 2 rpm settings-low and high. Per graph, it activated at the low setting. Which one did you move up?
I see similar behavior for AT trucks, which causes upshift delays.

 

Sorry, I forgot to mention that:

LOW: 4300 rpm
HIGH: 4400 rpm

So nothing should be activating before that

 

Those two RPM settings don’t (by themselves) “trigger” the ACIS system. They’re simply two parameters that define the three operating windows of the ACIS system.

 

Do you know why even if I put those high rpms in there, the ACIS is still activating under those RPM?

 

As stated, those values do not trigger the ACIS system by themselves. It simply defines the three RPM windows for ACIS.

The low value sets the threshold from the "low" RPM window to the "medium" RPM window.
High value sets the threshold from the "medium" RPM window to "high" RPM window.

From 0 RPM to the "low" value, is your low RPM window. From the Low value to the high value is your medium RPM window. From the high value to your rev limiter is your high RPM window.

Simply changing the values doesn't change the ACIS function - just the RPM's where the ACIS would ordinarily function.

You then have TPS windows and load thresholds that need to be met and further define if the ACIS is to be activated or deactivated. It's not a simple on/off switch.

 

Whoa thanks a lot for this explanation! Really the best explanation I've read on those parameters.

Is there any way to adjust the TPS windows and load thresholds to ACIS activation points? I have not seen any map for those