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How to Choose an Electric Fan

2010 April 24
by admin

Whether we’re at events or on the tech line, how to choose an electric fan is one of the questions we answer very, very frequently. While Flex-a-lite offers electric fans designed to bolt right into quite a few factory applications, we’d like to take this opportunity to help guide you in measuring your car of 4×4 to fit it for an electric fan.

The first step is to make sure you want an electric fan. Click here to read our article on electric versus belt-driven fans for more information on that topic.

To choose your electric fan, we recommend that you determine the minimum airflow you’ll need, because you’ll want to rule out fans that won’t cool your vehicle. Consider the following minimum cubic feet per minute (CFM) ratings for basic engines:

  • 1,250 CFM for a 4-cylinder
  • 2,000 CFM for a 6-cylinder
  • 2,500 CFM for a 8-cylinder

A further note is that engines that are 5.0-liter (302 cubic inches) or larger should use an electric fan with 2,800 or more CFM. Obviously, an 800-horsepower engine will need more cooling than a 400-horsepower version regardless of the cylinder-count, but this basic guidance will get you started. And no amount of CFM will keep an engine cool if the radiator is under-sized or if too much of the grille-opening is obstructed. But let’s move on, assuming that you have a typical engine in a typical enthusiast’s car or 4×4 with a proper radiator.

Now that you know the minimum CFM required, you need to determine what will physically fit. This is easiest to do if you remove the belt-driven fan and fan shroud so that you can accurately measure the radiator and the distance between the radiator and engine components. Measure the radiator core; the finned surface between the two tanks. Watch this video for step-by-step instructions.

You’ll want to select one of our fans that covers as much of this space as possible. In many cases, you may be better off with a dual fan because the shroud will pull air through a larger area of radiator than a single fan. Next, measure the distance between the radiator core and the closest engine component.

A few rules of thumb that we’ll pass along from our experience:

  • Don’t use an electric fan as the primary fan on 4-core radiators. It overworks the fan to try to draw air through these extremely restrictive radiators.
  • It’s recommended to have at least 70-percent of the radiator core covered by the fan shroud.
  • Use puller electric fans (mounted behind the radiator) for primary cooling. A pusher (mounted in front of the radiator) is appropriate as an auxiliary fan.

These general guidelines should address most of the questions and issues you run into when trying to determine which electric fan will fit on your application.

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