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Thread: 08 corvette fan logic?

  1. #1
    Tuner in Training
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    08 corvette fan logic?

    so I'm struggling with the logic of this os.
    so pwm fan is designed to come on from 15% to 90%.

    I go to the lowest setting box, like 191 or whatever it is, set it to say 30% (I've tried Lower too) then 40,50,60 ect and coolant temp goes well past 191 before it starts ramping in fan % on scanner. it doesn't really get the fan up to 30% till more like 217deg which then cools quickly back down and turns off again(below 15%) about 214. seems to not follow what I put in the boxes at all. seems like there's a filter in the logic how it ramps up the % slowly and back down again.

    I'm hoping to get the car to run about 200deg. as of now I have a 180stat that really seems to open more like 197 cause that's what it will get down to cruising, but stopped the fan comes up very late and gets to 217 at a light and then swings back down as soon as I'm moving. big radiator and big fan too just can't get it to turn to keep the idle Temps down around 199

  2. #2
    HP Tuners Support
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    It doesn't have to be perfect, it just needs to be done in two weeks...

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  3. #3
    Tuner in Training
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    I had read that link like 4 times and it just didn't match what I was seeing. not till I put all 40% in every box and the fan % stayed 0 and didn't come on did it hit me. the ecm is really only meant to control 2 relays, they are just using some math filter to make those 2 relay on points into % output. it in no way outputs the % you put in the temp box. so anything under 40ish you get nothing, above that you get say 50% duty cycle, like having one fan on. then at some point when the 2nd fan would come on, let's say 90% it will ramp the % up to max speed.

    so as a test I took the stock curve, copied it and pasted it 2 boxes lower and wow the fan percentage point moved down by that amount. it ramped up and down around the coolant temp set point the 2 boxes lower amount. so I ended up moving the curve to the left once more, that ended up with 191 deg box with 27 in it, so it didn't run at first start up. it now holds the temps right about 205. where stock is about 215 it seems.

    I might tweak it some more and target 199-200. but it's a cool day and only takes about 20% fan to start dropping and cycles on and off below run speed. so I'll mess with it more on a warmer day.