Deceleration Settings (91' NA Miata B6ZE)

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fan
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Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

Hi all,

Per @AndreyB 's request I'll put the problem here as a new thread.

What I have:
- 1.6L B6ZE Miata 1991
- MAP signal tee'd from the fuel pressure regulator
- Wideband (LC-2)
- Stock on-off TPS (I have a vTPS on hand, thinking about installing this week)

What I experience:
- RPM dips too much when the engine decelerates from ~4k RPM to idle by an abrupt change in throttle (I'll try to reproduce and log)
- cranking sometimes fail (I have logs https://rusefi.com/online/view.php?log=85)
- tune at https://rusefi.com/online/index.php?vehicleName=Miata&user_id=1253&sorts%5BuploadedMsq%5D=-1&sorts%5BuploadedLog%5D=-1

Any help is much appreciated. I can experiment with suggestions from you all :)
OrchardPerformance
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by OrchardPerformance »

Are you using the automatic idle? As in not the fixed idle valve position?

I think this is related to an issue we have seen with the miata before.
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fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

I think yes?
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by AndreyB »

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Gepro
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by Gepro »

In the log, you have trigger errors. There is a problem somewhere, the cam sensor wire is fine ?

Have you set the 20kPa in fuel VE table ? This line looks set too low to me, but I can be wrong. Maybe try to set the 20kPa line like 30kPa.
But for sure, we need the logs of the deceleration in order to help you :D
fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

Hi Gepro,

Thanks for the suggestions! BTW, how can I remove the 20kPa row from the VE table?

I did another autotune run today for 30 minutes. Stalled maybe 5 times, but I don't know if it's really deceleration-caused. I think it's probably linked with power steering, as stall happens almost all at turns.

Tune: https://rusefi.com/online/view.php?msq=300

Log: https://rusefi.com/online/view.php?log=87

Also, idle is always above 1000 though the target RPM is 960. I think it's the idle control valve settings, but I tried the constant offset (37-30), and it still keeps idling at 1030, and dips every ~30s to 900 and back.

Log for idling: https://rusefi.com/online/view.php?log=86

There is a WARNING in the gauge, though I don't know how to display the actual warning message...
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by mck1117 »

Ok, after a closer look at your log, I have a few notes:

- the idle isn't returning down low enough probably because the minimum position is actually set too high
- I'm not sure what the idle dying is, though it could just be that the idle controller isn't catching up fast enough to load from the power steering.

I'd multiply your whole VE table by maybe 1.1 or 1.2, as auto tune does a better job when leaning out than when trying to richen up from a lean misfire like you're seeing. It can also help to set the autotune to "very fast", then drive around very gently (slow throttle movements) and try and hit most of the map. That'll get you close much faster than driving around "normally" with the autotune set to "normal".
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by Gepro »

Are you sure about the idle valve ? Did you check it ? On NA it is really common a bad idle valve.

For the 20kPa, you can set the same value that 30kPa and keep 20kPa line. You can tune it later.
fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

I think there needs to be a function to test the IAC valve by setting it to a predetermined number? If you look at the logs you will see that the minimal IAC output is above 30%, while the rpm is ~100 rpm faster than the target rpm.

I will try multiplying the VE table and autotune again today.
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by AndreyB »

fan wrote:
Sat Dec 26, 2020 5:28 pm
I think there needs to be a function to test the IAC valve by setting it to a predetermined number? If you look at the logs you will see that the minimal IAC output is above 30%, while the rpm is ~100 rpm faster than the target rpm.
That's an example of a proposal which I am unable to comprehend. I really need your proposals but please articulate them with more details, knowing that ^^^ is an example of something at least I am unable to comprehend completely.

What would the test do? Would test execute while engine running or stopped? What is the expected behavior of the test?

Just to make sure can we unhook IAC connector for a second to confirm that this engine even goes below target RPM? In case of a vacuum leak your RPM would be above what we can control. While that's probably not an issue it helps to know for sure :)

"Idle Air Valve" test button would blip IAC to 80% open for a few seconds to confirm that IAC is functional at all.
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fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

Hi Andrey,

My suggestion is that we should have a manual IAC override (like a slider or text box) that can temporarily change the "raw" IAC percentage (in PWM %) in the "Bench Test". This would immediately determine if it's a controller issue or an IAC issue.

I can try unhooking the IAC (though I need to search how to do it) :)
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by AndreyB »

fan wrote:
Sat Dec 26, 2020 6:28 pm
My suggestion is that we should have a manual IAC override (like a slider or text box) that can temporarily change the "raw" IAC percentage (in PWM %) in the "Bench Test". This would immediately determine if it's a controller issue or an IAC issue.
This looks like "manual" idle with a slider which is pretty available
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fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

Oh never realized that :P

Will try!
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by mck1117 »

note that the manual slider is multiplied by the CLT curve depending on the coolant temp
fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

I tried the manual slider today and discovered that it can't go under 1000 however I change the setting. @AndreyB is right, I could have a vacuum leak somewhere. Will do more experiments tomorrow.
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by AndreyB »

What about your OEM ECU, does it go below 1K?
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by stefanst »

Make sure the throttle can close all the way. Many an idle-tuning session has been fubared by throttles cracked open slightly and randomly.
Also: NA6 Miata idle valve is funky. Sometimes the rpm goes up at lower settings. At least so I've heard- I have not confirmed this myself.
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by AndreyB »

stefanst wrote:
Sun Dec 27, 2020 6:42 pm
NA6 Miata idle valve is funky. Sometimes the rpm goes up at lower settings.
I believe I've experience that myself - after some specific value less duty cycle gives you more air due to weird geometry, maybe that's how fail safe is implemented?
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by mk e »

AndreyB wrote:
Sun Dec 27, 2020 6:53 pm
stefanst wrote:
Sun Dec 27, 2020 6:42 pm
NA6 Miata idle valve is funky. Sometimes the rpm goes up at lower settings.
I believe I've experience that myself - after some specific value less duty cycle gives you more air due to weird geometry, maybe that's how fail safe is implemented?
Possibly related, I've been messing with a tach and though all was well but during calibration I notice there are 2 very distinct ranges, right around 25%DC.....increasing DC and controlled, controls,...needle jumps 1500rpm whish is about 10% DC change. Start and and begin decreasing DC and controlled...then a jump in the opposite direction. The frequency I test at doesn't seem to help but does shift the points a little. the biggest random cap I had didn't seem to help, 1uF. Stupid inductors....I suppose like the coil in the IAC?

My next test is th just try a different supply voltage to get away from the problem range. On a TB, intentionally adjusting the TB to not need to problem area of the IAC? just guessing so ignore if its stupid.
fan
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by fan »

I think this is what I experience. IAC below 30% increases the idle, up to ~1800rpm at 0%.
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Re: Deceleration Settings (91' NA Miata B6ZE)

Post by mck1117 »

fan wrote:
Tue Dec 29, 2020 7:40 pm
I think this is what I experience. IAC below 30% increases the idle, up to ~1800rpm at 0%.
Hmm, might be a good idea then for us to implement a feature where it can "remap" 0% and 100% to some other spots in the range. Like you'd set [0, 100] -> [30, 100] since below 30 it actually adds idle air, and shouldn't try to use that range.
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