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Thread: LS2 Fan Logic or lack thereof?

  1. #1
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    LS2 Fan Logic or lack thereof?

    I have been playing with the fans for awhile now, and I can't figure it out for the life of me. Why couldn't they have stuck with the 04' logic, on-off, simple.

    What I want it to do is kick on fan 1 at say 180 and shutoff at 175, then if it goes to 185, kick on both fans. Can anyone explain how to do this? Thanks.

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  2. #2
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    Apparently the OS restricts the fan flexability. The best you can do is turn it on at 192 deg.

    I set all the values to 90 ( percent I think )

  3. #3
    http://www.hptuners.com/help/vcm_edi...ystem_fans.htm

    the relay controlled fans are driven by the same tables as the variable speed fans.

    Just that they convert the desired % to a state and then drive the relay logic depending on the state. You need to set either the desired % so that the state is achieved *or* change the state thresholds in the next table.

    State vs. Desired % converts the desired % to a State.

    Output Control vs. State decides which relays are on for a particular state.

    Either way you cannot get control of the fans below the lowest temperature, unless you are running our 2bar OS.
    I count sheep in hex...

  4. #4
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    I read the help file 10 times, and I still would never have figured it out. Wait a minute, I still don't understand how to make it do what I want...
    www.outlawpontiacdragseries.com
    Come race with us in MA, PA, and VA!

    2005 GTO A4 - Spintech X-pipe with Powerstick mufflers, IAT relocate, Volant, !scoops, !cowlgasket, !skid plate, LM-1, HPT2.0/MPVI Pro USB, 275x40x17 Nitto DR, rolled fenders, Pedders 2985 springs, Britax baby seat with 5 point harness.
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  5. #5
    you can't make then come on at anything below 192F unless you use our 2bar OS.

    Well, you can... just that they will be on all the time.

    Chris...
    I count sheep in hex...

  6. #6
    Senior Tuner S2H's Avatar
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    what chris is saying is you can olny make it come on as the lowest at 192 with the stock OS cause thats the lowest value...If you put 100% in all the cells then you will still only get 192* as the lowest temperature possible


    if you go to the 2 bar OS (have to set the map values to match your 1 bar sensor 10.33~94.34) then you can mod the OS to be lower than 192* and can set them to come on earlier
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  7. #7
    actually if you put 100% in all of the table the fans will stay on all of the time.
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  8. #8
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    If you put a 90 in the 192 bucket, the fans will come on right away even when its stone cold. Why does it do that?

    How do I make it run the 1 fan at 192 then and both at 196?
    www.outlawpontiacdragseries.com
    Come race with us in MA, PA, and VA!

    2005 GTO A4 - Spintech X-pipe with Powerstick mufflers, IAT relocate, Volant, !scoops, !cowlgasket, !skid plate, LM-1, HPT2.0/MPVI Pro USB, 275x40x17 Nitto DR, rolled fenders, Pedders 2985 springs, Britax baby seat with 5 point harness.
    Stock:13.36@104
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  9. #9
    if you put 90% in the 192 cell, that corresponds to state "2" from the state table. Then if you look at the output control table you see that for state 2 both output 1 & 2 are on for this state.

    here how your setup works (again). Working backwards this time.

    Look at the Ouput control table, this says that:
    State 0 = no fans
    State 1 = 1 fan
    State 2 = 2 fans

    Now look at the state table, at desired 50% it will transition from state 0 -> 1 (no fans to one fan). And at 90% it will transition from state 1 -> 2 (1 fan to 2 fans). It also says that when desired drops below 50% it will transition back from state 2 -> 1, and then when it drops below 25% it will transition from 1 -> 0.

    Now what you need to do is set up the commanded % to fall in the correct state for the number of fans you want.

    So, to switch one fan on you have a desired % like 51% (ie. greater than 50% but less than 90%). And to switch both fans on you need to have a number like 91% (ie. greater than 90%). You'll notice your stock file has numbers like this.

    Then, to switch back from 2 fans to 1 you have a number like 49% (ie. less than the 2->1 state % but higher than the 1->0 state). Then to go from 1 fan to none you have a number like 25%. Again you'll see the stock calibration uses numbers like this.

    The bottom line is you have no control of the fans below 192F (thanks GM). You will always have none, 1 or 2 fans on depending what you % you put in the 192 cell. As i said before, the only way around this at present is to run our 2bar OS which gives a range of 163-250F for the fans.

    If you want the fans to come on earlier, copy everything from the 221F cell and up, down to the 192 cell. Everything will happen 29F earlier.

    Chris...
    I count sheep in hex...

  10. #10
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    Thank you Chris. That makes sense now.
    www.outlawpontiacdragseries.com
    Come race with us in MA, PA, and VA!

    2005 GTO A4 - Spintech X-pipe with Powerstick mufflers, IAT relocate, Volant, !scoops, !cowlgasket, !skid plate, LM-1, HPT2.0/MPVI Pro USB, 275x40x17 Nitto DR, rolled fenders, Pedders 2985 springs, Britax baby seat with 5 point harness.
    Stock:13.36@104
    Mods in sig:13.02@106.5

  11. #11
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    yes, thank you Chris...that was definitly informative.
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

  12. #12
    Супер Модератор EC_Tune's Avatar
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    BTW: This also applies to the CTS-V IIRC.
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  13. #13
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    there are alot of new vehicles that use this logic it seems...even the 06 impala tuned I looked at recently is the same.
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

  14. #14
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    Quote Originally Posted by soundengineer
    what chris is saying is you can olny make it come on as the lowest at 192 with the stock OS cause thats the lowest value...If you put 100% in all the cells then you will still only get 192* as the lowest temperature possible


    if you go to the 2 bar OS (have to set the map values to match your 1 bar sensor 10.33~94.34) then you can mod the OS to be lower than 192* and can set them to come on earlier
    so if i change map sensor linear, map cylinder offset and map sensor linear b i could use my stock map sensor with the 2 bar operating sysytem. That would be awesome. i just want access to the lower fan settings.

  15. #15
    Senior Tuner 5_Liter_Eater's Avatar
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    This is a great explanation but I'm not sure that all this applies to all "LS2" fan tables. My '05 vette tune has all zeros for transition% VS: state and all 1's for output control VS: state as does the latest GM stock tune for the '05 vette. So the only real table for me is the desired % VS: ECT which I have at 50% at 192 ramping up to 90% at 207. I guess mine is not relay based and acually varies the voltage to the fan? Could be specific to the '05 Y-bodies.

    PS: I rarely see temps over 198 with my 160 t-stat and current fan settings.

    Quote Originally Posted by Chris@HPTuners
    if you put 90% in the 192 cell, that corresponds to state "2" from the state table. Then if you look at the output control table you see that for state 2 both output 1 & 2 are on for this state.

    here how your setup works (again). Working backwards this time.

    Look at the Ouput control table, this says that:
    State 0 = no fans
    State 1 = 1 fan
    State 2 = 2 fans

    Now look at the state table, at desired 50% it will transition from state 0 -> 1 (no fans to one fan). And at 90% it will transition from state 1 -> 2 (1 fan to 2 fans). It also says that when desired drops below 50% it will transition back from state 2 -> 1, and then when it drops below 25% it will transition from 1 -> 0.

    Now what you need to do is set up the commanded % to fall in the correct state for the number of fans you want.

    So, to switch one fan on you have a desired % like 51% (ie. greater than 50% but less than 90%). And to switch both fans on you need to have a number like 91% (ie. greater than 90%). You'll notice your stock file has numbers like this.

    Then, to switch back from 2 fans to 1 you have a number like 49% (ie. less than the 2->1 state % but higher than the 1->0 state). Then to go from 1 fan to none you have a number like 25%. Again you'll see the stock calibration uses numbers like this.

    The bottom line is you have no control of the fans below 192F (thanks GM). You will always have none, 1 or 2 fans on depending what you % you put in the 192 cell. As i said before, the only way around this at present is to run our 2bar OS which gives a range of 163-250F for the fans.

    If you want the fans to come on earlier, copy everything from the 221F cell and up, down to the 192 cell. Everything will happen 29F earlier.

    Chris...
    Bill Winters

    Former owner/builder/tuner of the FarmVette
    Out of the LSx tuning game

  16. #16
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    Quote Originally Posted by 5_Liter_Eater
    This is a great explanation but I'm not sure that all this applies to all "LS2" fan tables. My '05 vette tune has all zeros for transition% VS: state and all 1's for output control VS: state as does the latest GM stock tune for the '05 vette. So the only real table for me is the desired % VS: ECT which I have at 50% at 192 ramping up to 90% at 207. I guess mine is not relay based and acually varies the voltage to the fan? Could be specific to the '05 Y-bodies.

    PS: I rarely see temps over 198 with my 160 t-stat and current fan settings.
    I have have the same fan tables as you.It would be nice if chris can give us a quick lesson.

  17. #17
    Супер Модератор EC_Tune's Avatar
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    The C6 has a Pulse width modulated fan. Eg. variable speed.
    So it's super simple on the C6:
    Put the % of fan speed that you want it to run at the temperature that you want it to run.

    I use something along this line:
    Labels 192 196 199 203 207 210 214 217 221 225 228 232 236 240 243 247 250
    Fan Desired 0 50 60 70 80 90 90 90 90 90 90 90 90 90 90 90 90

    But any chance we can get an OS mod (Like MAF Patch/TCS Patch/FAN Patch) as an OS Switch setting?

    Setting it from 163F - 250F like the 2bar setup would be great!
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  18. #18
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    I installed my 160* stat today. Here is the information that i got. First, i upgraded to a 2 bar os so i could get the fan settings down to 163*. I then copied over my map settings under engine diagnostic's, airflow, map sensor from my stock bin so i didnt have to purchase a 2 bar map(thanks soundengineer). Using this table, i got the fans to cycle on and off between 172* and 190*.

  19. #19
    This is all great, but what if you have a truck with a mechanical fan with electric engagement? How does it work then?

  20. #20
    Quote Originally Posted by BADSZ28
    This is all great, but what if you have a truck with a mechanical fan with electric engagement? How does it work then?
    You have an EV, electro-viscous Fan Clutch that is controlled by a PWM signal. In effect the electronics replaces the spring on a standard old school fan clutch. (So EV clutches have the same leakage resulting in fan engagement for a couple min when the engine is first started.)

    The HPTuner tables and controls work like the "simple" C6 described above. (EC_Tune used 50% and 60% in his example but could have used 15% 99% etc. So don't confuse 50% with one electric fan on here.)

    So tell the fan to come on at 8% and it will lock the clutch up to 8% of engagement regardless of engine RPM. There is no state etc, just a percentage of clutch lockup.

    Why 8% lockup and not 8% of engine RPM???

    So engine is turning 1000 RPM and you ask for 0% fan... The fan will still be spinning. Same for 100% you will not get 1000 RPM out of the fan as the clutch still slips a few hundred RPM. 1000 RPM and 50% commanded does not equal 500 Fan RPM. Also the clutch slips more at higher engine speed due to increased fan load at higher RPM's. Your clutch range is 20-30% of engine speed at 0% fan commanded and 70-90% of engine speed at 100% fan commanded due to fan clutch design. (Range: 20-70% Light duty clutch and 30-90% is a heavy duty clutch.)

    Because a mechanical fan takes lots of power there is no advantage to bringing it on sooner for 160 degree stats. (It is already spinning 30%) You would loose more power than you gain. It is also possible to spin the fan faster than the engine. High speed with low engine RPM can have road speed airflow spinning the fan -- another reason to delay engagement. If you look at your factory setpoints for this EV fan you see that they bring it on as late (Hot) as possible to avoid the power loss and hopefully let you finish the 1/4 mile or hill climb before it kicks in.

    Now for Cold TBSS AC in 120 degree weather while at idle, yes, bring the EV fan on sooner than factory.
    Last edited by WarWagon; 05-04-2008 at 02:34 AM.