The heat generated from stop-and-go-driving, racing, and towing can kill engines. A well-designed electric cooling fan is critical to prevent engine overheating—a good fan will provide the airflow needed to dissipate excess engine heat with the least impact on horsepower and fuel economy.
Without airflow, a radiator is not much more than a holding tank for hot coolant. Optimizing the air movement across the fins of the radiator is essential to prevent overheating—a task that electric fans can often handle better than engine driven fans. The key advantage of an electric fan is increased engine cooling at idle when it is most needed. In addition, replacing an engine-driven fan can increase horsepower and improve fuel economy by eliminating the drag of the engine-driven fan.
We contacted the engineers at Maradyne to learn more about what makes good electric fan design–and what you should look for when choosing a fan. Maradyne electric fans are spec equipment for several NASCAR Nationwide and Cup Series teams—a demanding application where cooling is critical to winning. Maradyne uses that same racing technology to build electric fans for daily drivers, street rods, muscle cars and off-road vehicles.
Factors that Impact Fan Performance
According to Maradyne, factors such as blade width, blade pitch angle, number of blades, and blade velocity impact a fan’s overall performance. Taking these factors into account, Maradyne engineers calculate the optimal angle of airflow through its fan at three points—the hub, the middle, and outer blade tips.
The next step is to make the fan design fully functional by optimizing fan blade pitch at the static pressure and rpm conditions that replicate most automotive applications. Essential aspects of high performance fan design include:
- Balanced blades to prevent additional stress and wear on the motor, which can shorten its lifespan.
- Amperage draw to achieve maximum performance using the least amount of current.
- Concentric rings to tie fan blade tips together. For example, two rings (one outer and one inner) are used on Maradyne’s 16-inch fans to add stiffness to the blades and prevent them from flexing rearward into the shroud at high rpm. Smaller 12 to 14-inch fans have one outer ring preventing blade flex and distortion. Theses rings also reduce noise by preventing harmonic vibrations that can occur when individual blades rotate at high speeds.
- Sealed motor that can withstand dust and humidity.
- Practical design and testing. This testing allows performance to be further optimized. Maradyne says its tests are made at various static pressures to measure airflow, speed, torque, and amperage draw. Validation of a fan design comes in the form of on-track and off-road racing teams.
Choosing a Fan
Here are some factors Maradyne considers important when choosing a electric fan:
- Size the fan to the radiator core. A fan must cover as much of the radiator core as possible. When measuring, do not include the cooling tanks on each side or top and bottom of the radiator. These measurements will give you an idea of what diameter fan is required. You may find that you will need a dual fan setup to cover the radiator core. • Match airflow to the vehicle. Because it doesn’t generate as much heat, a stock or mild street engine doesn’t as powerful a fan as a strong street or race engine. Maradyne fans have motors that range from 130 to 225 watts; motor power determines the amount of cubic feet per minute (cfm) of air a fan delivers. If you plan to upgrade your engine, it won’t hurt to install a more powerful fan now—you can control its airflow with a temperature sending unit.
- Pusher vs. puller. The majority of automotive fans are set up in the puller configuration to pull the air through the radiator from the grill opening area. This keeps the fan out of the natural airflow path into the radiator. If you have space issues, you can use an electric fan in a pusher configuration in front of the radiator. Some fans can be used as either a pusher or puller.
- Shrouding. A fan shroud helps improve cooling by channeling air into the radiator core. If you have room for one, Maradyne highly recommends using a shroud.
- Power draw: The more powerful a fan is, the more current it will draw from your vehicle’s electrical system. Twelve- to 16-inch fans can draw from 15 to 28 amps, while some dual fan applications can draw up to 35 amps. Make sure your electrical system can handle the addition of an electric fan.
Check out this Maradyne video that goes into more detail on choosing the right fan.