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Thread: PLX, V2 Voltage Offset - HELP!

  1. #31
    Lifetime Member Bruce Melton's Avatar
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    Standing by, please let us know how that works.*

    * M300 and SM user.

    2000 C5 Coupe, 6M, Callies/Mahle stroked LS7 (441), Blackwing, Halltech, LS3 intake, 90mm Shaner TB, ported L92 heads, FAST 50# inj, not too much cam, Kooks 1 7/8" headers , 3" catless mid pipes, Z TIs, track suspension, , 3:90 rear, EFI V2, LM-2, etc.
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  2. #32
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    I had been using an innovate up until a few weeks ago until it shat itself. So I bought a PLX to trial it.
    First up I noticed it was a fair bit off in the readings compared to an Autronic that we have on the dyno, so looked into why.
    Checked the voltage with the O2 sensor unplugged and it was 2.3 or very close, which was shown through the V2 A/D input in EFILIVE, thought that was pretty close. So plugged in the O2 sensor again and it started at 2volts or so and climbed upto the free air reading but went upto 5.5volts by the efilive. Thought that was a bit far out since it should of been 5v max.
    So then I got the multimeter out and measured actual volts. With the O2 sensor unplugged the reading showed 2.32v on the multimeter and through efilive, about spot on. O2 sensor back in showed 4.95 on meter and 5.5 on efilive. Gave the car a run for a few minutes and shut it off and the volts showed 2.35v on the meter and 2.8v through efilive.
    So what I found was a voltage reading difference only when the O2 sensor was plugged in.
    Recalibrated efi to show same volts as multimeter and all is sweet.

  3. #33
    Lifetime Member Chalky's Avatar
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    What was involved in calibrating PLX in EFILive? Are you using SM-AFR?

    I have had some discussions with the folks from PLX. They claim that EFILive has a max of 40 Milli amps while PLX only supports 20 milli amps. PLX did an upgrade on my SM-AFR to support 40 milli amps. I didn't notice any difference in AFR readings. PLX thought the difference in amperage might have caused a misreading in AFR.
    2015 Z06 A8

  4. #34
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    Its in the V2 control panel (ctrl + f11). once you get a stable voltage on the plx, punch in what your multimeter says into the first voltage (usually around 2volts) then a higher volt around 5v then hit calibrate. it gives instructions on the screen.
    I'm not sure if this will sort the whole range or just between the two ref voltages. but it sorted the range I needed as well as down to at least 12:1. As long as you get a stable reading.
    Its an SM-afr.

  5. #35
    Lifetime Member oztracktuning's Avatar
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    The issue is caused by earth offset voltage resulting from the wiring resistance of the PLX device. This is why it varies in its error. The best way to make it stable is to use low resistance wiring more direct the battery.
    Oztrack
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  6. #36
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    Yeah thought of that as I was unrolling about 3 meters of the supplied power lead of about 1mm wire. Was much easier with a few key strokes to offset the offsets.
    Will look into some heavier power lead.

  7. #37
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    Quote Originally Posted by dc_justin
    A better bet would be to add .03 to a calculated PID in calc_pids.txt. This file will not be overwritten with future software updates whereas sae_generic.txt will.
    I found the location of the calc_pid text, its practically empty, do I cut and paste the file from the sae_generic file?

    Thanks

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