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Thread: Afr adjustment problems E38 L98

  1. #21
    Junior Member
    Join Date
    Aug 2009
    Posts
    16

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    Hi All,
    After many attempts to change the AFR from 14.63. I have come to terms with myself, (Ha ha) that it cannot be done in closed loop. I have fiddled with the PE and that seems to meet my needs. It is a fine line to where i map WOT and general good throttle response. I have keep the values above 2,500rpm for WOT. I also made PE come in quicker when PE is enabled and at lower MAP. It still needs a little fine tuning. I am also working on the spark table.
    Another interesting issue I noticed, is the high level of intake valve temp on cruise. On a really hot day I got up to 175 DegC. This made the engine very susceptible to knock. So I have drastically reduced spark at lower MAP range from 50 Deg to 38 Deg. This has made the INVT drop to 155 DegC, which has allowed me to increase spark on the acceleration. This was only done once I had properly calibrated my MAF and VE. The car is very smooth at cruise and seems to be better on throttle response. This was where I came up with trying to increase AFR to 14.00 so I could increase spark at lower MAP and keep temp in Chamber down.
    please could some comment on this as to whether I am opening myself up to issues I am not aware of when reducing cruise spark

    Regards

    Mark

  2. #22
    Lifetime Member
    Join Date
    Dec 2007
    Posts
    1,143

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    Quote Originally Posted by VEGASROBBI View Post
    So, would you say B3671 is the blend factor the ECM applies to modify the ethonal tables? Rather than name it AFR Commanded would it not be better to label it Blend Factor Applired and use Lambda as the units?
    Its actually an AFR table though to reference the base fueling from.

    i.e. on gas if the MAF says 14.7 parts by weight of air per unit time then it looks up this table and injects 1 part by weight of fuel for normal gas.

    Lambda stays the same. AFR changes with different fuels.

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