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Push oR Pull Fan


EF Ian

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I'm going to be fitting an electric fan to my 260Z and I was thinking about using a Pusher fan as it looks smarter inside the bay imo. But I have heard that they don't work quite as well, is this correct?

 

 

Obviously one drawback is that it will block some airflow from the radiator but it can't be that much can it?

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I also heard, so this is strictly speculation but, a pusher fan should only be used when supplemented with a puller fan, like a mechanical clutch driven fan, or the like. If you think about all the air from just moving down the road smashing into a fan, then trying to push that same air again, it just doesn't seem very efficient if you ask me. Hopefully someone with more knowledge on the subject will chime in. That being said, I'm going to run an electric puller fan on my motor.

Edited by OldAndyAndTheSea
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"Puller" fans are more efficient. It has more to do with the properties of air low. Your get better flow over a heat exchanger (in this case a radiator) by inducing a low pressure over the back side and drawing the air through it.

 

Trying to "push" the air through the front creates much more turbulence and much less actual air flow per unit of energy consumed by the fan motor.

 

If you look at any industrial heat exchanger, like say your home air conditioner, you will see this is how they are all designed. It's just the characteristics of fluid dynamics.

 

With cars though, things like proper engineering take a back seat to style and packaging.

 

Oh, and having the obstruction of the fan assembly in front of the radiator isn't any worse than having it behind the radiator. Wherever it is in the path of the air flow it will be a restriction.

 

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Puller fans with a proper shroud will work better. I think a pusher fan should only be used when space is a major issue

This^

 

Look at how OEMs build stuff. They have millions of dollars invested in cooling designs that work. They all use pullers with shrouds and usually air guides on the front too.

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"Puller" fans are more efficient. It has more to do with the properties of air low. Your get better flow over a heat exchanger (in this case a radiator) by inducing a low pressure over the back side and drawing the air through it.

 

Trying to "push" the air through the front creates much more turbulence and much less actual air flow per unit of energy consumed by the fan motor.

 

If you look at any industrial heat exchanger, like say your home air conditioner, you will see this is how they are all designed. It's just the characteristics of fluid dynamics.

 

With cars though, things like proper engineering take a back seat to style and packaging.

 

Oh, and having the obstruction of the fan assembly in front of the radiator isn't any worse than having it behind the radiator. Wherever it is in the path of the air flow it will be a restriction.

 

Thank you.  Even though this wasn't my thread, I once again leave more educated than I came.

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  • 6 months later...

Accidently stumbled onto this thread looking for something else. I went to the wrecking yard and got a Ford 2 speed fan complete with the shroud. This fits my Radiator perfectly, and looks like factory. I got one off of a big ford, I think a mercury marquis a Lincoln (93 to 96). This coupled with the triple relay and double sensors at 190 and 210 degrees keeps my 350 cool. In fact, I wired it so that the fan comes on high speed when the A/C is turned on which makes it run two needle widths toward cold on a hot Texas day with the A/c running! These fans are killer. The fan shroud from the big fords will have to be installed upside down and two of the plastic mounting ears cut off. I even moved the warning sticker from bottom to top. looks factory.

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  • 1 month later...

One last round on this subject.  The reason puller fans are more efficient than pushers is the shroud.  The shroud allows the puller to draw across the entire area of the radiator rather than just the circular fan diameter which is what you see with a pusher fan.  

Conversely, however, if the fan can generate enough airflow it doesn't matter if it is a pusher or a puller.  The goal is to get enough air across the radiator to remove the necessary heat to control engine temperature. The shroud, however, allows the OEM to use a slightly smaller fan and use less power to do the cooling which means less parasitic power loss from the engine.

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Puller fan also wins as you'll be drawing in cooler air from outside the engine bay through the radiator, instead of pushing hot engine bay air through the radiator.  This creates an uphill battle, as you're heating the "thing" that's trying to cool the other "thing".

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Puller fan also wins as you'll be drawing in cooler air from outside the engine bay through the radiator, instead of pushing hot engine bay air through the radiator.  This creates an uphill battle, as you're heating the "thing" that's trying to cool the other "thing".

 

 

.......

 

Sigh.

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OMG! - Yes, pusher fans are mounted on the front of the radiator.  I'll bet someone has installed one behind a radiator and then complained about overheating problems and wondered what the problem was.  I can see the post.

The fan would break in no time if installed behind the radiator, the motor would constantly be fighting the air coming in to the bay from moving forward which would try and spin the fan the opposite way.

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I picked up a porsche 924 cheap to flip back in 1988 and it would overheat only when driving around at neighborhood speeds.

 

I figured it out when I walked past the bumper in shorts and felt the warm air coming out the front.

 

It seems the early 924s had fan motor connectors you could easily connect 180 degrees off.

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  • 1 month later...

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