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-   -   Still tuning Idle on my MSM, need some guidance, perhaps in person (https://www.miataturbo.net/megasquirt-18/still-tuning-idle-my-msm-need-some-guidance-perhaps-person-96690/)

VcrMiata 05-14-2018 11:28 PM

FYI - pulled this from a few sources:

Noticed that your engine state settings don't have any hints in your release.

From the MS3 Tunerstudio MS Lite Reference for 1.5 manual:
Fast acceleration threshold
When RPMdot is above this threshold, your engine is considered to be accelerating quickly. This should be set to slightly below what is normal for WOT in a low gear.

Used by Closed-loop idle control, idle-VE and idle-advance.

Slow acceleration threshold
Between this value for RPMdot and the fast accel threshold, your engine is accelerating slowly. It should be set as low as possible to catch all actual acceleration, but not set so low that it catches RPM jitter.

Used by Closed-loop idle control, idle-VE and idle-advance.

Fast deceleration threshold
Below this value for RPMdot, your engine is decelerating fast. This should be set to a value that is slightly above the RPMdot when you rev high and then let the engine fall back to idle. Use an RPMdot value from the middle of the rev range.
Below this threshold, as long as the engine is at least slowly decelerating, the engine is considered to be in overrun.

Used for overrun fuel-cut control, idle-VE and idle-advance, idle-VE, idle-advance and overrun fuel-cut.
Slow deceleration threshold
Between this value for RPMdot and the fast threshold, your engine is decelerating slowly. To set this, cruise in a high gear, then see what RPMdot value you get by lifting off the throttle fully and decelerating. Set this value slightly above that RPMdot value.

Used by Closed-loop idle control, idle-VE and idle-advance, idle-VE, idle-advance and overrun fuel-cut.

In 1.5.1, the following hints are provided (I'm not sure if the behaviour was changed when the fast settings were removed):
Slow acceleration threshold(rpm/sec):
When RPMdot is above this threshold, your engine is considered to be accelerating. It should be set as low as possible to catch all actual acceleration, but not set so low that it catches RPM jitter.
Used by Closed-loop idle control, idle-VE and idle-advance.

Slow deceleration threshold(rpm/sec):
When RPMdot is more negative than this value (larger), your engine is decelerating. To set this, cruise in a high gear, then see what RPMdot value you get by lifting off the throttle fully and decelerating. Set this value slightly above that RPMdot value.
Used by Closed-loop idle control, idle-VE and idle-advance, idle-VE, idle-advance and overrun fuel-cut.

Braineack 05-15-2018 08:34 AM


Originally Posted by airbrush1 (Post 1481656)
Quick question about Over-run fuel cut... I was still having intermittent stalls coming to a stop that weren't always reproduce-able. Doing some reading in the manual and elsewhere, I started looking at these numbers. I have things Idling pretty darn well a this point (was even able to drive comfortably to work without the laptop this morning), even experimenting with closed loop idle settings has worked out well now that with your help my open loop is dialed in very well. Turning OFF Over-run fuel cut seems to completely solve the intermittent stall issue, so I'm looking at my settings (same as in the above posted tunes since I hadn't adjusted it at all) to see if they should be changed, or is it just fine to leave over-run turned off completely (I'm not super concerned with the fuel savings it provides, since I rarely drive the car to begin with)? Obviously if its advantageous to have over-run cut working correctly, I'll use it, as I hate having features worth using that I'm not taking advantage of!

I've attached a log of the stall on my way to petco this evening, since it just so happened to occur


see wall of text (paragraph #2): https://www.miataturbo.net/megasquir...3/#post1482220


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