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Thread: Push or Pull

  1. #1
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    Push or Pull

    I fitted my electric fan with thermostatic controller on the inside of the radiator and when running pulls air from the engine bay and in theory pushes through the radiator, fine if the car is stationary, in a situation where the car is moving forward with air being forced through the front of the radiator and the fan running then you have a situation of air travelling in both directions and being forced to act against each other. This raises a question! What is the theory or optimum usage of an electric fan ie is it to pull air over the hot engine and to eject it through the radiator or to pull cool outside air through the radiator over the cooling fins to cool the radiator and to some degree the engine. Depending on whichever is the most efficient then i may have to rewire my fan motor to change its blades rotation.
    Any thoughts welcome.

  2. #2
    Join Date
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    I think the purpose of the fan and thermostat is to provide cooling when the car is not moving. If they are working together when the car is moving then either the thermostat setting is not right or the radiator is not providing sufficient cooling.
    Dek

  3. #3
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    The fan on a car should be drawing cool air in through the radiator, not to push hot air out of the engine bay. Remember you are trying to cool the coolant which cools the engine. When driving fresh air is pushed through the radiator. When stopped the fan either pushes air through if it is in front of the radiator or pulls if behind.
    It sounds like your fan should be pulling as it is engine side.
    Paul

    SRV8 - 429 Ford Big Block, 4 speed toploader

  4. #4
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    Pulling air from the outside is the only way, also best to make a shroud so you are pulling cool air over the whole radiator. If you think about it your fan will only kick in when you are stationary and you want cool air from outside not warm air from your engine compartment.

    Baz

  5. #5
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    Dont just assume changing the rotation to a sucker from a blower will be all you need to do. If your fan was specified as a puller or pusher the fan blade angles will be more efficient one way . Look for an arrow on the blade. You might have to flip the blade round.
    A cowling will also increase the efficiency. Of air flow. I have a cowling and some rubber flaps which open on the move and.close when the fan needs to.operate in slow traffic.
    The fan distance from the radiator also reduces or increase the air flow.
    Last edited by jon1d; 15-06-21 at 10:14 PM.

  6. #6
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    The above posts are all correct and is definatly worth fitting a cowl .
    My set up consists of twin two speed fans with an over ride switch .
    Make sure you use a 70 amp relay with good connections as these
    things will loosen and burn out .
    Chris.

  7. #7
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    Forgot to add mine pulls the air through and has never been a problem.
    Chris.

  8. #8
    Join Date
    Feb 2007
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    I’ve never heard of a fan pushing air out through the front of a car!
    I have however heard of small fans being fitted inside the wing vents to draw air out of the engine bay. Doubt they’d be much use whilst driving, but may help dissipate heat when stopped?
    Simon

  9. #9
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    Another vote for pulling air from front to rear through the rad'. This makes sense in many ways but the obvious one is that if you were to push warm, engine bay, air from the rear to the front, apart from being inefficient at cooling the water there would also be a point if moving slowly where the airflow from vehicle movement would balance the airflow from the fan and you'd get no water cooling at all.

    I've never had the need for a cowl so never fitted one, I can see the benefit of this when the fan is working but always been a bit worried about it negatively affecting airflow when the fan is not working although in practice it doesn't seem to be a problem.

  10. #10
    Join Date
    Dec 2019
    Location
    amersham
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    Thanks for the replies gentlemen.
    All comments make sense, so now i need to change the rotation of the fan motor and flip the blades so the blade curve trails in the direction of rotation as specified by the manufacturer/supplier.

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