[neovin]

here are some of the docs and links i have put together to help me

[iltheo84]

During these holidays I managed to get my Speeduino installed and configured in my car.

To my surprise, it fired up pretty much right away, with close to no tweaking except for some little adjustments in the idle area of the VE table, since the engine was running quite lean.

My next step was setting up open-loop idle, as I was trying to test my IACV valve PWM limits, and I had some confusing results.

Common values (as seen in forums and online guides) should be around 30% to 65% with an increase in RPM as the duty cycle goes up.
My tests showed minimum RPM at around 72% and engine speed increases as I reduce my PWM value down to 45%.
At 0% my RPM are still higher than at 72%, so my IACV seems to work in reverse

[PSIG]

Look at all of your available settings. There is an option to reverse operation. Click that.

Before clicking and assuming all is well just yet, know that many IAC valves have a low-Duty Cycle default position for a high idle, for if IAC control is lost. A "limp home" default. Either closely examine your valve for this possibility, or continue to apply greater DC when running to check if it is actually closing the default position (higher DC = lower rpm), then opening the normal operating range (higher DC = higher rpm).

An example is here. Note that if you are using an inefficient Hz setting, the minimum-flow area may be at a much higher DC.

[iltheo84]

Look at all of your available settings. There is an option to reverse operation. Click that.

Thank you PSIG, I know there is a Reverse option, but the point is a stock Miata IAC valve should not operate in reverse, and there is no info anywhere about a low duty cycle default for this IACV, it should simply be fully closed if disconnected or under a certain duty (normally around 30%).

I will try adding a flyback diode between the +12V and the switched ground wires, this seems to help in case of erratic behavior of the valve

[iltheo84]

I added a flyback diode wired towards the positive (white/red) wire, but it did not resolve my issue.

If any, now the IACV starts dropping the RPM at as low as 5% duty cycle

I also tried the Reverse option but RPM shot to 2000 at 1% PWM

I'm assuming I will have to take off the whole TB assembly and test the IACV on the bench

[pani]

There's nothing wrong with the behavior you are describing. Reverse the valve operation and that's it. Don't solve problems that do not exist. Move on to tuning.

[iltheo84]

I might have solved my idle issues, and maybe found a bug in the firmware?

After reversing the valve operation in Idle Settings, I could control the valve and raise/drop the idle speed by manually increasing/decreasing PWM value.

I then turned on Closed Loop Idle but it seemed to work in the wrong direction: as RPM dropped, it pinned the valve to the lowest duty.

Setting the valve back to Normal operation did not help, swapping Min and Max % did not work (PWM stayed at 0%), negative PID parameters are not valid, so basically Closed Loop did not work until I set the option to Closed+Open Loop, then it started using the valve in the right direction to stabilise RPM.

[theonewithin]

Sounds like a bug.

Also sounds like valve wired backward.

[iltheo84]

Also sounds like valve wired backward.

I'm using a PnP kit that uses the stock wiring
@pani is using the same board on the same car and he confirmed his valve also operates in reverse.
I'll look into it some more and maybe open a thread in the Bug subforum.

[neovin]

I'd be interested to see what's causing that, post up your tune with the bug, label it clearly and your current tune.

Logs if you have any also