It's no secret that engine accessories rob your engine of horsepower. Ever notice how the idle slows slightly when your air conditioning kicks on? That's because it's siphoning off power to operate the system.
Now suppose you could recover some of that lost horsepower siphoned off by an accessory. That's what installing an electric fan does. Instead of being driven by a belt attached to the engine, it runs off one or more separate electric motors, so it doesn't drain off horsepower. That means you can recapture as much 17 horsepower and 20 lb.-ft. of torque (depending on the vehicle and engine speed). Other claimed benefits include less wear on the water pump, reduced fan noise, improved A/C output, better gas mileage, and improved cooling.
How so? When your vehicle is sitting still, air is not being forced through your radiator. That's why you need an engine fan, because it supplies fresh air to your cooling system when you're at a stop. Normally, since the factory fan is attached to a pulley on the engine, the speed of the fan increases as the speed of your engine increases. But if your vehicle is idling at a stoplight, the fan is moving rather slow, and not moving much air.
An electric fan, however, operates off a temperature sensor, so it kicks on when needed, and automatically runs faster when the temperature rises. The Flex-a-lite unit shown here, for instance, comes with a variable speed control module that operates the fans from 60 to 100 percent, depending on engine temperature.
Driving speed will not affect the performance because an electric fan is not mechanically attached to your engine. When your vehicle is stopped or idling, an electric fan is capable of moving much more air than the factory fan. In addition, the shroud around the fan also helps to ensure that the fan is drawing in cool fresh air through your radiator, and not just moving warm air around your engine compartment.
Different engines have different normal operating temperatures, so an electric fan, such as this one, has a built-in thermostat that is easily adjusted. You can fine-tune the temperature at which your fan comes on by simply opening your hood and turning the knob on the thermostat. It's also possible to have the fan come on with the air conditioning system by splicing into a wire leading to the compressor.
Choosing the right electric fan may be as simple as picking a model designed for your particular vehicle. If your vehicle doesn't have a specific fan for it, you can do a custom installation using the adjustable mounting brackets included with the electric fan.
For a custom install, you'll need to figure out the dimensions of the mounting surface (defined as the finned core area). You'll also need to know how much depth is available for an electric fan while maintaining adequate clearance (at least an inch) around fan blades. Note possible obstructions to mounting an electric fan (air conditioning, transmission oil dipstick, power steering lines, wiring, overflow tanks, etc.).
When an electric fan is the primary cooling unit, use a puller type. A pusher is better for use as an auxiliary fan. Whichever type of electric fan you install, you'll be pleasantly surprised by how it affects your vehicle's performance.