In the vast world of hot rodding, many enthusiasts can get so caught up in building the ultimate powerhouse, that they tend to overlook their cooling system. Often is the case where a shadetree mechanic may upgrade the water pump, radiator, and thermostat in a project car, but then relies on a stock cooling fan to help keep his engine’s temperature in check.
When building a musclecar, one must consider the static pressure load created by heat and humidity. The only way to avoid it is upgrade every aspect of the cooling system – Troy Wood, Derale
While it may be possible to get by with a factory unit in a mildly-built car in the colder parts of the country, those of us living in more fervent areas should consider an upgrade. You wouldn’t solely rely on a generic box fan to keep your 10,000 sq. ft. home cool in the summer, right?
Despite the fact that the performance cars of today come with an electric fan from the factory, the classic cars built prior to the 1980s relied on belt-driven units, which is not only inadequate for a 500hp+ street machine, but it also robs power that could be getting put to the pavement. Less power to the ground means slower ETs at the dragstrip.
As much as we know about increasing the horsepower of an engine and shaving weight from our cars, some of us in the hobby are unschooled in the area of engine cooling. So we’ve decided to investigate on our reader’s behalf. In doing so, we contacted Derale Performance, the engine cooling experts, about their recommendations for electric fans on today’s hottest performance cars.
This meant getting in touch with the Derale Performance Sales and Marketing Manager, Troy Wood, and picking his brain about what the average gearhead should know about cooling fans. With the high cost of an engine build these days, the majority of our readers should probably pay attention to what he has to say.
The boys over at Derale really know what they’re talking about; they are among the biggest names in the business, and offer a complete catalog in cooling system components for just about everything; from pre-war hot rods, to late-model pony cars.
Power Automedia: What automotive markets does Derale currently cater to?
Wood: “Derale offers both electric and mechanical fans for the entire spectrum of four-wheeled vehicles, for enthusiasts wanting to upgrade only their cooling system components all the way to racers heading to the Salt Flats at Bonneville. We sell rigid race fans to high output dual fan setups with shrouds for tow vehicles, street cars, off-road racers and everything in between.”
PAM: Is it possible that a fan can be overkill, or simply too large for a customer’s application?
When doing a fan upgrade, Derale suggests complimenting your build with a transmission cooler upgrade. Derale offer’s several different kits. All of which include the hardware, an OEM-spec hose, and 5/16-inch cooler lines.
- PN# 12006: Standard Cooler Remount Kit- 4ft. 11/32-inch hose
- PN# 13006: Deluxe Cooler Remount Kit- 4ft. 11/32-inch hose
- PN# 13065: Deluxe Cooler Remount Kit with -6 AN fittings
- PN# 13064 Rigid Cooler Remount Kit- 8ft. 11/32-inch hose
Wood: “I don’t hear many customers complaining that a fan is doing too good of a job keeping temperatures under control, but often I hear the opposite. Many of our customers call and tell us about the improvements they’ve made to their engine’s cooling system, but once I ask them more details about their setup, you would be surprised with some of the areas they would overlook; such as the oil pan, thermostat, or in most cases, an ill-equipped radiator or cooling fan.”
PAM: At what point do you think a customer should upgrade their current setup to a larger, single or small twin setup? Can you give us some basics on this?
Wood: “Simply put, a dual fan setup is more efficient than a single fan due to the additional airflow being created across the surface of the radiator core. A dual 12-inch or 14-inch shrouded fan kit will be more efficient than a single 16-inch shrouded fan. Unfortunately, there are often space constraints that do not allow sufficient space between pulleys and other engine parts. We introduced an entire line of shrouded dual fans at the 2011 SEMA Show that have been very well received due to the compact size of these units.
We offer four versions ranging in size from 22-1/4-inch wide by 19 inches high, to 23-3/4 inches wide by 19-3/4 inches high. We can now give restoration enthusiasts who like the factory look a dual fan option that in the past was not available. In the old days, enthusiasts had to run a single fan as that is all that was offered, and then looked for additional auxiliary help in the form of a pusher fan in the front. Or they had to resort to a non-stock, oversize radiator and the modifications that would be required to go that route.”
PAM: Tell us your thoughts on comparing puller and pusher fan setups. Is one better than the other?
Wood: “Pulling applications are about twenty percent more efficient than pushing applications. This is because the electric motor, fan blades and housing block a percentage of the core of natural airflow. The percentage of which is determined by the size of the hub and motor assembly.”
PAM: How important is the overall idea of airflow and how does it affect cooling an engine?
Wood: “Airflow performance figures, as popularly measured in cubic feet per minute (CFM), is one of the most misunderstood, overstated issues faced today. All manufacturers base their cfm numbers at zero static pressure, simply because that is the highest figure attainable in a controlled environment. However, we operate in the real world, where ambient temperature, humidity and operating conditions are just the beginning of all things requiring consideration. Secondly, the figures being advertised range from reasonable to optimistic to ridiculous.
While the average seasoned-wrencher has no reliable way to measure airflow reliably or accurately, the amp load ratings are more easily determined. A good rule of thumb is one hundred cfm for every amp required. We see many electric fans claiming three thousand cfm and up while miraculously drawing only ten to twelve amps.
This does not correlate, and many people find out the hard way that the super performance electric fan they installed to cool even a mildly warmed over mill cannot do the job. Then they spend additional money looking for additional methods of cooling their ride when the problem is actually straightforward. Powerful, high-watt fan motors require electricity. Pure and simple. The question is often asked how much cfm is needed to cool my engine. What should be asked is can my radiator cool my engine, then can my fan cool my radiator.”
PAM: How important is choosing the correct alternator to run a high output Derale fan system?
Wood: “Our entry level performance electric fan uses a two-hundred twenty-five watt motor. From there they increase to two-hundred sixty-five watts all the way to three-hundred watt motors on our HO Extreme series fans. All of that requires enough juice to keep everything flowi so a high amp alternator is required if you have cooling issues.”
PAM: How is the radiator tube size and fan sizes related?
Wood: “All things being equal, more fan blade, whether larger in diameter or in area, will move more air. Blade pitch and the number of blades also affect performance. We have found that some of the newer thin blade fans with a higher number of blades spin faster at startup and can move more air… to a point. As static pressure loads increase, the same diameter fan with the same motor but with fewer, but thicker blades is a better option.
When ordering an electric fan, it’s best to know things like your pulley to fan clearance -Troy Wood, Derale
To truly help an enthusiast with a cooling problem, we usually answer their question with several of our own. First a customer needs to determine the level of the problem. A customer on a rod run in the south in August who is topping out at two-hundred fifteen degrees Fahrenheit requires a different solution than one pulling a trailer in Idaho or Colorado in wintertime and pushing two-hundred and thirty degrees Fahrenheit.
Our first question is always “how hot is it getting and how do you know?” It may sound redundant but more than a few respond that it is “pegged on H” on their factory “C to H” gauge. We are here to solve customer issues with the right solution for their needs, not using the “one size fits all” method commonly used by some.”
PAM: Earlier you mentioned that many overlook other aspects of their cooling system; can you give us some examples of what they are?
Wood: “We typically like to recommend that our customers run their cars solidly below the 200-degree mark. In which case a 180-195 degree thermostat is inefficient as it isn’t actuated until it passes that point. So it’s best if a lower temperature thermostat is used, such as a 175-degree unit. Also, an aftermarket oil pan coupled with an oil-cooler is another suggestion we would like to make.”
PAM: How important are relays, and are they often overlooked?
Wood: “Yes! Relays are often overlooked. Relays will take the amp draw away from your switch so it will last longer, providing more durability while providing a much larger contact surface for current to flow. This is much better for you charging system and fan.”
PAM: Can you explain to our readers how important a shroud is, are they necessary or are they determined by specific application?
Wood: “Fan shrouds are the most efficient way to use any fan in puller applications. They work on the same principle as wind tunnels, preventing airflow recirculation while simultaneously concentrating and evenly distributing air drawn through the radiator. A well-designed shroud can provide up to fourty percent more cooling efficiency than non-shrouded fans and minimize the “dead-zone” in the fan center where the hub and motor assembly are located.
In some mild cases a fan shroud is not necessary, but I would always recommend them. In pushing applications fans shrouds cannot be used as they simply block any air passing through the grille of a vehicle that is not funneling directly into the blades. They impede natural airflow over your core.”
Also, it’s best to invest in an aftermarket temperature gauge. It may sound petty, but you can’t rely on the factory unit, especially if it’s just a dummy light. I can’t tell you how many times we’ve seen guys spend over fifteen-hundred dollars in a cooling system, and overlook something as simple as a temperature gauge.”
PAM: Can you give our readers some basics they need to know when comparing straight and curved fans?
Wood: “Curved blade fans are quieter and tend to provide slightly more airflow than their straight blade counterparts and the reason is simple: air impulses on a straight blade fan are more direct due to the straight edge on each blade pulling air through. Each blade on curved blade fan pulls air at slightly differing times and the air impulses overlap, cancelling the airwaves each creates while spinning. A curved blade fan offers greater surface area than a straight blade fan as well, and that additional area creates additional airflow.”
PAM: Anything else that we need to consider when selecting a fan for a musclecar?
Wood: “When building a musclecar, you must consider the static pressure load. Static pressure is created by heat and humidity, and the only way to completely avoid it is to upgrade every aspect of the cooling system. You might not have this problem in a mostly stock car in the Northeast, but with something that’s been heavily modified and living in either the Southwest or Southeast, you almost certainly will.
PAM: In a hypothetical situation, a customer calls Derale to order a fan for a ’69 Chevelle with a big-block, what would your recommendations be?
Wood: “We offer electric fans for every application, however, since there’s such a wide array of possibilities out there it’s difficult to say. We would need to know things like their current radiator to pulley assembly clearance and shroud measurements, how hot their car is currently running at, what thermostat they use, and so on. It’s best if they have all of that information in front of them when they call. We don’t want to recommend the wrong fan assembly to a customer if we don’t have all of the facts about their vehicle’s setup. We try to make sure a customer gets what they need the first time they call us.”
PAM: In closing, can Derale provide our readers with any advice for troubleshooting?
Wood: “Absolutely! The best advice we can give any enthusiast is to know your car’s exact set up prior to ordering a fan. You also need to keep in mind what your car is intended for. The more information you can provide to our team, the better Derale can steer you in the right direction. It’s also important to take into consideration that everybody has different issues with different types of vehicles, so not every issue is common. To combat this, we’ve made sure to keep all of our doors open, including our tech line, which is conveniently available Monday through Friday. We’ll even begin taking tech calls as early as 6:30AM all the way through 3PM in the afternoon to answer any question about any of our products.”