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Thread: JTEC scanner set up

  1. #1
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    JTEC scanner set up

    just begin working on this new plataform and the first doubt comes .... how to set up VE error on this PCMs I can only see map in Volts and not in pressure (Kpa or PSi) any guidence will be great

    also i cant log spark advance or retard im lost on this new aplications
    BTW im working on a cammed and ported 1998 4.0 auto jeep wrangler
    i have it iddling and running just by adjusting based on the wideband reading but i cant make a correct adjust until i can log VE error the right way so lets see if anyone have a clue on this 1998 wrangler 40A3 silva stk.hpt1998 wrangler 40A3 silva base6.hpt
    all the way from Tampico bay Mexico

  2. #2
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    I've seen 2 files so far from a JTEC - this one and the sample posted in the thread above.

    Neither has VE tables that I can find, just direct pulse width and a strange PE table that doesn't make sense to me.

    Is there a commanded EQ, AFR or FAR channel?

  3. #3
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    JTEC does not use VE tables, the only thing you can do is log O2 correction and make changes to pulsewidth to get the fuel within 5%

  4. #4
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    That's what I was going to suggest. Log lambda and use current lambda over expected lambda as a multiplier on the pulse width table in the area you are working with.
    Last edited by spoolboy; 5 Days Ago at 01:37 PM.

  5. #5
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    The part throttle enrichment and wot enrichment are fuel air multipliers, on some JTECs there are delays for entering PE but most earlier JTEC cals have those zeroed out.

    You can use the part throttle and wot enrichment as you target lambda , make an excel spreadsheet, apply your logged lambda against your target lambda then use that multiplier to modify your pulsewidth fuel table.

  6. #6
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    yes but how i log the error if i cant plot speed density (rpm * pressure) ? cause i cant log MAP?
    all the way from Tampico bay Mexico

  7. #7
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    Quote Originally Posted by dlc_racing View Post
    yes but how i log the error if i cant plot speed density (rpm * pressure) ? cause i cant log MAP?
    You don't need to.

    The error is what you see on the gauge divided by what you want it to be.

  8. #8
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    This is actually much more simple than what you're thinking it is.....

  9. #9
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    ok i log lambda vs expected lambda (commanded vs requested) but wath will be the other axis? map volts?? so i can know were to adjust the pulsewith table ..sorry but my head is hurting to get a grip on this new format ..too much VE from GM and maf from ford
    all the way from Tampico bay Mexico

  10. #10
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    the 2 axis should be rpms/MAP kpa I would think. You want to log the same factors of the base fuel table which is MAP kpa(torr) and RPM.

  11. #11
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    sorry but the early jtec dont log map in pressure only in volts (1998 wrangler pcm) but the 2000 cherokee does so thanks for your help
    all the way from Tampico bay Mexico

  12. #12
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    Send a request in to support. Also, you could make your own custom math to convert it if you know the correct scaling for the map sensor.
    Last edited by spoolboy; 4 Days Ago at 12:53 PM.

  13. #13
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    I?m having same problems with logging my 98 xj. I?ve sent a case and they are definitely working on it. Can someone steer me in the correct detection on what?s base spark egr on and off. These engines don?t have egr I?m just assuming it?s labeled wrong.

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    Did either of you try to create a math channel in the mean time?

    Should be pretty easy to figure out V x X = kpa. And if the map cannot be rescaled above 105 for boost (which it seems like) making a math channel might be the best way to tackle this even if kpa is available.

  15. #15
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    I?m not currently in boost, but I?ll will to know this too. I?ve got a whole setup, just haven?t had time to finish it. But I do have a stroker 4.7 big cam, and lots of port work. She?s currently totally flat over
    4200rpm. I can?t log so I can?t adjust much yet.

  16. #16
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    Quote Originally Posted by spoolboy View Post
    Did either of you try to create a math channel in the mean time?
    Should be pretty easy to figure out V x X = kpa. And if the map cannot be rescaled above 105 for boost (which it seems like) making a math channel might be the best way to tackle this even if kpa is available.
    The equation is y=mx+b, where y is the map value, m is the slope, x is the voltage input, and b is the offset.

    To find the slope, you need to know 2 points of data (usually advertised at 0.5 volts and 4.5 volts - min and max).

    Just as an example of how to solve for "m" and "b", here are some arbitrary numbers:
    Say a 2 bar map sensor minimum output of 0.5 volts occurs at 20 kPa, and max output of 4.5 occurs at 200 kPa.

    (200 - 20) / (4.5 - 0.5) = 45
    45 is your slope (m)

    Now, using the slope, multiply it by either the min or max voltage to see what it outputs:

    45 * 0.5 = 22.5
    or
    45 * 4.5 = 202.5

    In either case, the offset to reach the advertised output at the corresponding voltage is -2.5

    20 - 22.5 = -2.5
    or
    200 - 202.5 = -2.5

    So, the math parameter for this sensor would be:

    y = 45 * x + (-2.5), and x would be your map voltage pid.

  17. #17
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    Thanks