1991 Miata MSPNP2 90-93 & AFR Innovate MTX inaccuracy in TS (Software Glitch?) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-12-2013, 09:37 PM   #1
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Exclamation 1991 Miata MSPNP2 90-93 & AFR Innovate MTX inaccuracy in TS (Software Glitch?)

*Attached is a JPEG of my "Air.Fuel Ratio" gauge(s)
*I have been having accuracy issues with my INNOVATE MTX wideband. The wideband reads 14.7 and the megasquirt is reading 15.0.
*I researched a lot on the forums; and consensus seems to point to bad grounding of the gauge. So I made sure the wideband was grounded properly on its own circuit.

*NOW FOR THE INTERESTING PART....I set the TS AFR "GAUGE STYLE" to ANALOG GAUGE and Bam! there is an inaccuracy
*As you can see in the attached photo, The DIGITAL reading of the gauge is 15.0 and the a ANALOG NEEDLE points to 14.7 (which is the same reading that appears on my MTX guage in the car.) So half the gauge is correct.
* Which value does TunerStudio read when Live Tuning VE tables? The 15.0 or the 14.7?

Please advise. Thanks in advance!
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1991 Miata MSPNP2 90-93 & AFR Innovate MTX inaccuracy in TS (Software Glitch?)-o2.jpg   1991 Miata MSPNP2 90-93 & AFR Innovate MTX inaccuracy in TS (Software Glitch?)-o2-2.jpg  
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Old 01-23-2014, 06:32 PM   #2
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Wow! Looks like I stumped y'all!
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Old 01-23-2014, 10:24 PM   #3
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I assume that the 15 is coming from the computer, therefore that's the value that MS is reading. I have the same issue with my PLX300. My gauge reads lower that MS. The problem may be in wiring, causing a voltage difference from what your gauge is reading and what is being received by MS. You're gauge is the correct value... at least that's what I've told.
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Old 01-24-2014, 10:19 AM   #4
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This sounds like a ground offset. Where exactly is the wideband grounded? It should be grounded to the block or cylinder head.
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Old 01-24-2014, 10:49 AM   #5
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Quote:
Originally Posted by slomiata View Post
Wow! Looks like I stumped y'all!
no, we just dont respond to things that have been covered in full...
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Old 01-24-2014, 11:09 AM   #6
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It's just latency in the graphical display. Values are averaged over time so our simple human eyes can process the info. If the display showed the actual sampling rate, the data would be jittery and difficult to understand. The gauges average at a slightly different rate. Also, your laptop could be laggy.
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Old 01-24-2014, 12:22 PM   #7
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BRAINEACK: Thanks for the reply. I searched the threads like a mad man and did find LOTS OF INFO regarding bad/shared wires causing gauge and TS inaccuracies ..............I understand all that.....but I never found the answer to MY QUESTION:

"Why does the gauge in TunerStudio show a 15.0 value, but the analog needle ON THE SAME GAUGE point to 14.7 (which matches my MTX)????" Which value is TS using for VE?

14.7 or 15.0
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Old 01-28-2014, 11:07 AM   #8
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I will need you to first answer my question before I can answer yours.
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Old 01-28-2014, 12:48 PM   #9
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(+) MTX wideband is powered off a relay that powers the autometer gauges.

(-) MTX wideband is grounded to a clean chassis ground that is not shared with anything else

As I read through the other posts, everyone seemed to have a different opinions about ways to get the gauge and MS to be accurate....some said isolate, other said share...some said scale the guage to make them make match.

I understand that the MTX and MS may not be jiving due to wiring issues....but I am confused because the the MS has 2 DIFFERENT READINGS....it doesn't make sense now matter how it is wired. The numerical value should match the analog needle...but it is consistently 0.3v off no matter what the reading

....and the analog needle on the MS matches the MTX...so how do I know if there is a wiring problem...
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Old 01-30-2014, 11:25 AM   #10
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In my experience, "good chassis ground" tends to be an oxymoron. Your best bet is to ground the MTX-L to the cylinder head or engine block.

The gauge looks like a visualization error of some sort - you may want to email the TunerStudio team directly at [email protected] with a copy of your project folder.
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