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Thread: How to interpret "Rough" tab in INPA

  1. #1
    Join Date
    Jun 2013
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    maine
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    1999 bmw m3

    How to interpret "Rough" tab in INPA

    Hi folks-I've been playing with INPA on my e36 m3 and came across a tab labeled "Rough". Its a bar chart of each cylinder with different values. Anyone have an idea of what these values mean and if they indicate any issues?

  2. #2
    Join Date
    Jul 2004
    Location
    Houston, TX
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    MCoupe, 328is, Z3, TDI
    They are a calculation based on crankshaft position sensor and how fast the crank spins by, to estimate burn quality.

    They should be close to the middle with a little fluctuation, all at idle.
    If a cylinder is bad, it will be way off.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

  3. #3
    Join Date
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    E70 3.0sd E21 323i
    Bear in mind that if one cylinder is bad, the readings for both the following cylinder and the opposite cylinder in the firing order will also be affected.

  4. #4
    Join Date
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    maine
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    1999 bmw m3
    Thanks. Not sure what you mean by the cylinder is "bad"? Is it a misfire, or is it a fault in the crank sensor?

  5. #5
    Join Date
    Jul 2004
    Location
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    MCoupe, 328is, Z3, TDI
    The crank sensor cannot fault on just one cylinder, it's reading from a toothed ring on your crank.

    One cylinder being 'bad' would mean the combustion is poor (even up to a misfire), possibly due to ignition coil/spark plug... or worse: loss of compression in that cylinder.
    The rough test is quite sensitive to poor ignition, showing a change before you even get a code for misfires.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

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