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Thread: Controlling LS2 Cooling Fans

  1. #1
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    Default Controlling LS2 Cooling Fans

    I am new to all this so if I’ve planted a boot in my mouth please forgive me.
    Engine LS2 with E40 ECU. Transplanted from 2005 GTO. Cooling fans in original car were controlled by the ECU in two modes via 3 relays. The primary request ran both fans in series at low speed and then the secondary request ran both in parallel at high speed.

    EFILive however provides for a graduated output from ECU against coolant temperature. My brain cell cannot see how a graduated demand can be made through the ECU primary/secondary signals to relays. I expected that there would be the same style of control as for LS1 i.e. Fan 1 turn on temp, Fan 2 turn on temp and Off temp.

    Can anyone shed light on this please?

    Thank you
    Terry

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    Hello Terry,

    I am the self professed Gen III guy - have only done a small number of Gen IV conversions at this point in time - so the following is what I believe to be true with respect to PWM fan control. Fan 1 and Fan 2 turn "on" temperatures and turn "off" temperatures are determine by the percentage value entered in the applicable table(s).

    The attached PDF file is an example of this process, in an E38 ECM with the EFILive cooling fan patch (extended temperature range) applied to the table values. The table numbers and appearance may be slightly different with your E40 ECM (I don't work with these controllers) but the concept applies.

    Hope this helps ...


    Regards,
    Taz

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    Hello Taz

    Thank you for an informative reply. That is the most sense I have seen so far on this topic. My brain cell is still at a loss to understand it completely though.

    It seems to be much more complex than it need be. Fan switch On I can follow in the examples where a range is given. Switch Off is not so clear. In the text you give values of 49 and 24% respectively for Fan 2 and Fan 1 off. In the table for the LH example the values are 23 and 47%.

    Is it that the quoted Off values or lower figures are valid? If that is so my brain cell can have a lie down.

    For interest the attachment is the parameters for the E40. To clarify, AC is not used.

    Thank you

    Terry


    Cooling Fan Tables.pdf

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    Quote Originally Posted by ODeer View Post
    ... switch Off is not so clear ... is it that the quoted Off values or lower figures are valid? ...
    Hello Terry,

    You've got it right ... quoted values or lower turn off ... quoted values or higher turn on - each fan (1 or 2) respectively.


    Regards,
    Taz

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    Hello Taz

    You are a star. Thanks for that, I'll give it a whirl. I still wonder why we don't have simple settings for each fan on and off. No doubt there will be some electrickery reasoning behind the current (unintentional pun) system.

    Thank you

    Regards

    Terry

  6. #6
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    The higher-on/lower-off values provide "hysteresis", this prevents the circuit from rapidly cycling on/off/on/off when the temperature is right on the boundary (if there were a single value).

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    Joe (Moderator) joecar's Avatar
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    So, the Discrete Fans setting means "series/parallel"...?

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    Quote Originally Posted by joecar View Post
    So, the Discrete Fans setting means "series/parallel"...?
    Hi Joecar ... yes sir. My understanding is the "Discrete" fan setting is for use with relays - like the OEM 3 relay setup used in trucks. Corvette tunes use the "PWM Electric" setting - for use with a fan control module.


    Regards,
    Taz

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    Good Afternoon Taz

    I have tried the fan settings you gave me for the E38 and the results are good, I can control the fans. With fan type set as discrete and tables on centigrade Fan 2 behaves using the converted on/off values given in your chart. Fan 1 though will react to 50% as start value as opposed to 25 – 89%. (It might even switch on at a lower value that I haven’t tried.) It turns off at your table value. All temperatures are +/- 1 degree and have been read from Scan/dashboard so should be those that the ECU is seeing.

    I’m very pleased to be able to set up the fans in this way. Once again thank you for your assistance and if I experiment and find more information I’ll post it. Next is to find why it idles at 800 rpm even when hot.

    Regards
    Terry

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    Old thread, but I need the info. I don't see the pdf file that Taz talks about is post #2. Can anybody give me some info on this? Thanks.

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