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Thread: Turbo 4.0 Jeep MAP Issue

  1. #1
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    Turbo 4.0 Jeep MAP Issue

    I?ve got a completely stock 1999 Jeep 4.0, I stuck a turbo on it and I?m currently trying to get it to have a closed loop tune. My issue is I cant get the 2 bar map to work with it. There?s no OS option like GM?s and I tried to halve all spark and fuel tables to match the 2 bar map sensor but it wouldn?t run after that. Also the scanner doesn?t work for my vehicle.Jeep first file pulled modded.hpt
    Last edited by Jisbell; 05-19-2020 at 08:52 PM.

  2. #2
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    you need to half the map scale multiplier under engine-airflow from 244-122, and also change your fuel and spark to match the new map sensor scale

  3. #3
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    Quote Originally Posted by Omunoz View Post
    you need to half the map scale multiplier under engine-airflow from 244-122, and also change your fuel and spark to match the new map sensor scale
    Thanks for this, have you got an example of the values / what the finished tables look like ? I am heading down this path at the moment - in this case a picture would be worth a thousand words, I think

  4. #4
    Advanced Tuner uarperformance's Avatar
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    So if its like early viper tuning you don't really have any scaling. You just work in the KPA area. There is very minimum amount of cells to work with in when you use a 2 bar map sensor. Its why most went aftermarket Fuel Management Systems. So injectors size has to be calculated into your VE table. its so generic that you cant over think it. when you turn the key on with the 2 bar map. That area is under that is where you start with your scaling down for injectors and that you have only a few rows to work in

  5. #5
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    i end up with 260 in the map characteristics with gm 2bar map =58kpa reading, this will differ depending with the type of sensor you use

  6. #6
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    Quote Originally Posted by Omunoz View Post
    i end up with 260 in the map characteristics with gm 2bar map =58kpa reading, this will differ depending with the type of sensor you use

    hi, thanks for that, so the oem scaling was 244 with the factory 105 max kpa sensor, you fitted the aftermarket sensor and changed the scaling to 260 instead of the 122 often seen
    is that 58 kpa then key on engine off ? I have got a MPX4250 map sensor which is a 2.25 bar sensor so should be pretty close

    and when idling under vacuum would you be in the 31kpa row ?

    then I get the tune by pulsewidth, to desired afr

    and did you attempt to adjust the axis column and row values or just leave them as is and use mental maths to derive a real world value ?
    Last edited by 3barboost; 12-09-2021 at 02:07 PM.