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Thread: Help me understand "Radiator Fans" please.

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    Default Help me understand "Radiator Fans" please.

    I am sorry for what sound like a stupid question.

    My factory car, has an upgraded 3 core alum radiator. I am still running the factory OEM fans with the small shroud. But I do see some high temps from time to time.

    However just like i upgraded my radiator, I am wondering if should also upgrade my fans. People also seem to upgrade their factory fan with aftermarket units from SPAL or others but the interesting thing to me is that the fans are of the same size... (so I see no point.. maybe one moved more air? - really?)
    so I am not sure if that even makes sense.

    Currently my car is a production car, factory ECU etc. The radiator fans work based on the engine temp (please correct me if I am wrong) and the car sends a signal to modulate their speed.
    Are fans in race cars ran manually by the driver and only at full speed ? if so why?

    Thanks in advance,

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    The Real Captain Slow Red_5's Avatar
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    Lots of race cars don't even have radiator fans. Fans are only needed when the car is moving slowly or stopped like when sitting on the grid. If you're only having cooling issues on track, I'd look some place other than fans. You might need hood vents or some other way to get the hot air out from under the hood. Or maybe you need to duct/ seal off the area around your radiator so air is forced through the radiator. Now if your car is overheating while sitting in traffic on your way home from work, new fans might be needed.

    Disclaimer: I'm a Miata guy, STIs might have special cooling needs I'm not aware of.
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    Quote Originally Posted by Red_5 View Post
    Lots of race cars don't even have radiator fans. Fans are only needed when the car is moving slowly or stopped like when sitting on the grid....
    really, is that so? A friend of mine actually turn on his (a/c) heater to full hot I guess to get the fans running to cool off the car.

    Temps on STI's increase on boost. (higher boost)

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    Quote Originally Posted by FoxSTI View Post
    really, is that so? A friend of mine actually turn on his (a/c) heater to full hot I guess to get the fans running to cool off the car.

    Temps on STI's increase on boost. (higher boost)
    F1 cars don't have fan. they can't see more than 1 minute without overheating.
    reason running heater at full hot helps is because you are adding in another radiator (heater core). since there is no moving air inside the cabin, you must use a fan to move air through a heater core.

    it sounds like in your case, it isn't fan related. you might not have enough thermal capacity to remove the heat your car is making. but before installing more cooling items, first make sure your current system is working at its peak efficiency.

    1. running distilled water instead of coolant
    2. idea is to create pressure delta front of radiator vs, rear of radiator. like Red_5 said, seal up all holes around radiator, so air must travel through radiator fins instead of going around it.
    3. same as above, but on rear side of radiator: you don't want air to enter engine bay, you want it to exit engine bay, lowering air pressure. so add hood vent (where it is low pressure on hood area), seal up bottom of the engine, so air do not enter engine bay there.
    4. many add an aftermarket air filter, without boxing it up. Then take out a headlight (or pipe in) to let "cold" air in. This raised air pressure inside engine bay, making radiator less effective. so make a box for air intake.
    5. do the same thing for oil cooler. which is just another radiator.
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    Quote Originally Posted by FoxSTI View Post
    really, is that so? A friend of mine actually turn on his (a/c) heater to full hot I guess to get the fans running to cool off the car.

    Temps on STI's increase on boost. (higher boost)
    Using the cars heater is an additional way to cool the engine, you're pulling heat out of the coolant to warm your car. Turning the AC on will activate the AC fan which might be good while not moving very fast (or not at all) but shouldn't move more air through the radiator than a car driving 80+ mph.
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    Having too thick of a radiator can also impede cooling due to a lack of airflow through the core. Thus, a fan upgrade may be needed to help suck air through a thick core. If you have a properly sized (fin count, and thickness) radiator, then typically fans are a restriction when the car is at speed -as others have already said.

    On a coolant/additive note, NanoPro MT's "NanoCool" (available at AutoZone) is WAAAAY better than Water Wetter or any other additive out on the market.

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    Quote Originally Posted by Stuntman View Post
    Having too thick of a radiator can also impede cooling due to a lack of airflow through the core. Thus, a fan upgrade may be needed to help suck air through a thick core. If you have a properly sized (fin count, and thickness) radiator, then typically fans are a restriction when the car is at speed -as others have already said.

    On a coolant/additive note, NanoPro MT's "NanoCool" (available at AutoZone) is WAAAAY better than Water Wetter or any other additive out on the market.
    Thank you for sharing. Have you tried their Oil stabilized?
    are you running nanocool on your car? if so what do you mix it with?
    Last edited by FoxSTI; 07-18-2017 at 02:49 PM.

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    Yes, I've worked with them for 8 years now. Your oil will run cooler with the nano oil stabilizer since it greatly improves the heat transfer ability of the oil.

    Depends if the car is a track or street car. For street I'd dilute the antifreeze as much as you stand to, and add nanocool. For a racecar, I would just use water and nanocool.

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    Quote Originally Posted by Stuntman View Post
    Having too thick of a radiator can also impede cooling due to a lack of airflow through the core. Thus, a fan upgrade may be needed to help suck air through a thick core. If you have a properly sized (fin count, and thickness) radiator, then typically fans are a restriction when the car is at speed -as others have already said.

    On a coolant/additive note, NanoPro MT's "NanoCool" (available at AutoZone) is WAAAAY better than Water Wetter or any other additive out on the market.
    Is that legal to run on racetracks?

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    If your car still has factory power, I don't see the reason why it would overheat with an oil cooler.
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    Maybe I'm making more power. Lol
    But on Sport or sport# all sti start to run hot.

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    Quote Originally Posted by ucfbrett View Post
    Is that legal to run on racetracks?
    Yes.

    Quote Originally Posted by jqsti2015 View Post
    If your car still has factory power, I don't see the reason why it would overheat with an oil cooler.
    Because you're on track? -most cars run hot on track and can benefit from improved oil cooling, which NanoPro's oil stabilizer does.

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    Do you run the factory splash tray underneath? On a few cars, if you remove that, it ruins the airflow through the radiator.
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    Quote Originally Posted by Force McCocken View Post
    Do you run the factory splash tray underneath? On a few cars, if you remove that, it ruins the airflow through the radiator.
    yes I do.

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    Thank you everyone for all the replies. I am guessing the answer to my OP is that fans are there only for when the car is standing or driving very slow. Upgrading fans will do nothing for cooling during tracking.
    Do we know for a fact that the fans turns off during higher speeds? If they are spinning at full speed and the car is running in at the track (inifield for instance) would it impede performance and efficient of the radiator?

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    The fans are triggered by coolant temperature. Are yours coming on? Just let the car idle in your driveway and watch the temp gauge. They are one speed, usually. On/Off. When they are on, they do incur a fairly large electrical load on the electrical/charging system, so to that end, yes, they do impede some power, but it's necessary.

    Some old-school tricks are to parallel wire your A/C fan to your radiator fan, so when the main fan comes on the AC fan comes on without engaging the AC compressor.

    You may also want to check the health of your cooling system. Air in the system, bad radiator cap, blockages, cavitating water pump, slipping belt on the water pump, corroded/work waterpump impeller blades, corroded thermister sensor (triggers the fans), etc.
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    ^ yes they do come up while idling. So then then answer to my question is that they will be on regardless of what I am doing at the track is I reach a certain coolant temp.
    I was under the impression that radiator fans worked on a PWM signal that dictated their speed. Not just full on or off.

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    RaceTape Ninja Force McCocken's Avatar
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    Maybe search for your particular model on model-specific forums.
    Yer pal,
    Force

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    Quote Originally Posted by Force McCocken View Post
    Maybe search for your particular model on model-specific forums.
    yeah... the problem with that is 90% of those people are street / parking lot racers...

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    What radiator do you have?

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