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Thread: LS2 Fan Logic or lack thereof?

  1. #61
    Tuning Addict blindsquirrel's Avatar
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    If the min/max breakpoints are the same for the aftermarket fans as for the OEM ones, you should be using 91% or more to command 'off' (make sure the first cell in both tables is an 'off' value), and 15% or less to command full speed.

    A/C Clutch status and A/C pressure (both in volts and KPA) are available channels. There are also channels for fan desired % and fan actual %, as well as fan on/off status.

  2. #62
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    I tried 91 and they would not turn on. I watched the scanner and the temp at which the fans finally turned in and it it was the temp where 85 was the %

    Before I reversed the ect desired % boxes. The fans turned on at 212? and the stock tune had it at 18.

    So I used that as my max speed.
    Last edited by fifty; 09-24-2020 at 08:49 PM.

  3. #63
    Tuning Addict blindsquirrel's Avatar
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    Maybe it's 85%/10%. (or, the same 15% from one extreme/10% from the other, same margins as the OEM but just with the duty cycle reversed)

    You can find the off/on transition point easy enough with the scanner. Key on engine off, engine cold, go to manual controls, command the fan ON then increase the % until the fan starts up.

    But, with this jacked up combo you might have to start at 100% ('off') and ramp it down. You're in uncharted territory here.

  4. #64
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    I tried that. I couldn’t get the scanner to turn the fan on. Started at 1% and went up to about 40% and it never turned on.

    So I did about 5 “tunes” lol. I know I have my low number right (the 85) but I’m not sure if 18 equals 90% (the guy at spal told me not to exceed 92% max speed, I think he even suggested 86 or 87 as the number to put in the tune)

  5. #65
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    I have a related question regarding my 2010 NNBS HD 6.0 (E38 PCM) with dual E fan conversion. I've wired everything up as if it were a non-hd truck utilizing pin 58/17 on the ECU as ground triggers and wired them to the factory fuse relays. I can get the fans to turn on low and high speed using special functions in the HP Scanner to override-- this tells me that the wiring is correct.

    After verifying that the wiring is correct I tried using the programmed logic in the PCM to turn the fans on without luck. They should turn on at 199.4 degF (51% as I have it programmed) but they don't.
    I have them programmed below:
    HP Tuners Fan Programming.jpg

    Am I missing something? Is there something else that can be keeping these fans from turning on? My understanding is that as it is currently programmed, the low speed fan should turn on at 199.4 (51%) but its not. I run it as hot as 210 degF without the fan turning on by itself.

    Any help is greatly appreciated.

    Cheers!
    Last edited by ZforSpeed; 09-25-2020 at 02:34 PM. Reason: adding more detail

  6. #66
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    Got my fans running. Post #3 in this thread pretty much covers the logic. The problem I was having is I didn't have advanced features enabled. For any other newbs out there, you have to go to your Editor --> Edit --> View --> select Advanced. This will enable the advanced options and in this case allowed me to change the [output control vs state] table to enable low speed fan for fan output 1 and high speed fan for fan output 2.

  7. #67
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    Quote Originally Posted by fifty View Post
    I tried that. I couldn’t get the scanner to turn the fan on. Started at 1% and went up to about 40% and it never turned on.

    So I did about 5 “tunes” lol. I know I have my low number right (the 85) but I’m not sure if 18 equals 90% (the guy at spal told me not to exceed 92% max speed, I think he even suggested 86 or 87 as the number to put in the tune)
    Did you unlock your advanced features and look at the Fan Output Control vs Current State table?

    Here's mine: fan output control vs state.JPG

  8. #68
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    Yes. But mine looks a bit different. I will try to post a pic of it in the morning

  9. #69
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    fan tune home screen.pngscreen shot fan details.png

    I "believe" the fan is running when driving according to ect temp. However when I have the scanner running, the fan pid never shows on, its always off. Also when I turn the ac on the fan doesnt turn on either. I have turned the ac pressure on the scanner and it will go 2600 kpa.

    The desired % graph uses the same fan numbers as the "fan desired % vs ac". The ect desired % graph starts at 212 degrees and goes to 245 degrees I think. Top temp isnt too important. (When using the spal brushless fan, I had to invert the desired numbers... so start high and end low)

    Im trying to figure out what the following graphs do and if I need to adjust them to make the fans work for the ac (and possibly the ect when driving):

    1) Fan output 1 vs current state
    2) fan output 2...
    3) Fan output 3...
    4) Desired ECt torque Zones
    5) Fan state transition % vs Current state

    Most of the stuff on fans is older gm and not applicable and the tuning school book doesnt get into these details.

  10. #70
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    I reversed The fan state transition desired % vs current state Numbers
    So now they read:
    Fan desired
    0->1 45
    1->2 30
    2->3 20
    3->4 10
    1->0 48
    2->1 36
    3->2 24
    4->3 12


    I have no idea what they mean or what they do. But the fan was running when I had the ac on. But the ect jumped about 10-12? when I had the ac on so I need to get the fan moving a little fast at those water temps. I think it’s set for less than 45% speed. So maybe I’ll make the fans turn on at 212? like factory at a low setting (15% speed) and then for the next temp boxes ramp it up to 70% speed and then the last half of the water temp boxes at 90% (so reversed it would be 18% in the tune)

    If anyone can tell me what that graph I have listed does or means and why it would be what let the ac turn the fan on, it would be greatly appreciated.

  11. #71
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    Changed the fan speed a bit to help keep things cooler. And adjusted the ECM graph 18040- "Fan State Transition Desired % vs, Current State" to:


    0->1 77
    1->2 65
    2->3 54
    3->4 41
    1->0 79
    2->1 69
    3->2 59
    4->3 44

    (Im still not sure why that let the fan turn on for the AC activation before. Hoping someone can chime in what this graph does still)

    And the new fan speeds from 212* to 255.2* are:

    85 50 40 35 35 35 35 30 30 35 20 18 18 18 18 18 18

  12. #72
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    that table is your fan state 0=off 1=fan1 on, 1>2 is fan2 on, 2>1 is fan2 off, 1>0 is fan1 off, the values is when it changes based on the fan desired % v ect when it reaches 77 at what ever temp u have that against it will then cause the fan state to turn on fan 1 and so forth for the fan 2 at a hotter temp, in terms like stock make the 0>1 put 50 and then in the desired % v ect put 51 in the temp u want fan 1 on, then in the 1>2 put 90 and then in desired % v ect put a 91 in the temp u want fan 2 on at, just make sure the 0>1 is lower like 25 and lowest desired % v ect cell is 24 so fans turn off, easiest to just keep factory logic just change the ON values to suit when u want them to come on/off, the a/c settings are based on a/c pressure so work little different, best to get a stock tune if yours it way out to look at and get a base point to start from
    Last edited by 07GTS; 10-04-2020 at 01:43 AM.

  13. #73
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    So if the truck only has 1 fan....(oem was a single fan and I’ve replaced it with a single spal fan)... so I’ve had to reverse all the % numbers.

    I’m reading your post and trying to sort through it....

    So are you saying that even though on my desired % ect graph where I have the ecu commanding 85% (reality it’s the starting slowest setting for the spal fan) for 212?, the fan will not turn on because my “fan state transition desired vs current state” graph says 0->1 77?

    So the fan won’t turn on until it hits the temp associated with the 77% desired (which would be somewhere between 212 and 216?)

    I’m confused then as to why it would have 4 more fan possibilities, why would they have 4->3 44? I think the oem settings for 4->3 was 45 and 0->1 was 10 and the 212? desired % was 4

    I’m trying to follow...

    And what was weird was until I reversed that - "Fan State Transition Desired % vs, Current State" graph, the ac wouldnt trigger the fan. Once it was reversed the ac triggered the fan. Even though the desired % vs ac had already been reversed.

  14. #74
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    i think fan3 is a/c which is also controlled by other means but u can set it off using the fan state 3 relay trigger, and 0>1 is an off function or a 0>1 is on function same with 1>2 and 2>1, dont worry about the extra fans 4-5-6 they are just there not doing anything, not sure on your exact setup as mine is factory twin fan, does yours just need 12v trigger ? or is it speed controlled

  15. #75
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    Oem is a pwm ev... factory harness is 3 wires. +/- and a signal. So spal and others said to use the white wire in the fan for signal.
    Tune is still pwm ev and 100hz (spal said that is fine)

  16. #76
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    your ecm 18047 i would have thought if u put a 1 in the zero column it should bring fans on all the time ? or does the fan work when u turn it on in the scanner controls ?

  17. #77
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    The fan does not work when I click “on” in the scanner controls. Nor does it show “on” when it’s on in the scanner pids

  18. #78
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    I will try changinig 18046 to having “1” all the way across. It is currently 0 1 0 1 0
    I’m not sure why I would need to change it from stock. Since it is supposed to be the table that says “turn on in this state” and if I want it to turn on the same way as factory... then it shouldn’t change.

    But I’ll try with 1’s all the way across abs see what happens. I won’t be able to try until Tuesday at the earliest though.

  19. #79
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    its just a test to see if the fans are actually working then all u have to setup is the on/off points, should only need a 1 in the zero column telling it with no state to turn on, but if u can control it in the scanner would be easier

  20. #80
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    The scanner will not turn them on. Also, when they are on, the scanner shows off.