We have a love affair with diesel trucks. They get great mileage, are tough as an anvil, and respond to modifications in ways that gasoline engines can’t match. Just keep adding air and fuel until your diesel engine of choice makes over 1000 ft-lb of torque. Well... maybe it isn’t quite that simple, at least not anymore. California recently introduced strict emissions laws for diesel-powered trucks, and other states are following suit. This means that the days of high horsepower programmers that dump more black smoke than a freight train are quickly coming to an end.
Fortunately, there are new and innovative ways to make more horsepower from your diesel truck without negatively affecting emissions. One of these methods isn’t really new at all; Flex-a-lite has been building radiators, electric cooling fans, and related cooling products for over 40 years, but until recently they did not offer anything specifically for diesel engines. Fortunately, they now offer direct replacement electric cooling fans for late model Ford, Chevy, and Dodge diesel trucks.
While modern fan clutch assemblies are more efficient than the direct drive mechanical cooling fans of old, they still take power to spin. This, in turn, reduces efficiency, which costs horsepower and mileage. Electric fans are typically lighter and more efficient than mechanical fans, but they have traditionally had two weaknesses: inability to keep up with the heavy loads diesel trucks are famous for; and custom fabrication for proper fitment. Flex-a-lite addressed both of these issues by integrating dual 15” S-blade fans that move a whopping 5500 cubic feet of air per minute (CFM) into a custom-fit aluminum shroud with applications for all popular late model diesel trucks. Other thoughtful features include a variable speed control depending on the load, air conditioning input, easily adjustable rheostat, and the ability to shut the fan off completely if needed.
Flex-a-lite claims an increase of as much as 27 horsepower, a 6% increase in mileage, and an installation time of four hours. Curious to put their claims to the test, we ordered up part# 262 for our 2002 Cummins-powered Dodge Ram. The first thing that caught our attention when we pulled the fans out of the well-padded box was what a masterpiece the TIG-welded shroud is. It is a shame to have to hide products this nice under the hood! Ford Power Strokes and Dodge Cummins use aluminum shrouds, while Chevy Duramaxes use an equally nice reinforced nylon injection molded shroud. All Flex-a-lite products are made in the USA, and our application included fan motors constructed by our neighbors to the north in Canada.
We went to Ken Imler Diesel Performance for the installation, who has installed dozens of these fans in the past. It took lead technician Steve Scott less than four hours with most of the time devoted to cleanly routing the included wiring and relays. Fit and finish of the shroud is perfect, including fitment of the coolant overflow tank and wiper fluid reservoir. Combined with the excellent instructions (Flex-a-lite includes detailed instructions, complete with illustrations. Can’t see enough detail in the black and white photos? Flex-a-lite has complete installation instructions on their website, complete with color photos that you can enlarge at the click of a button), it’s an easy day project for the home mechanic.
With the Flex-a-lite fans installed and wired, we put the Dodge on a Mustang Dynamometer to find out how much power we gained. The output of our Cummins increased by 14 peak horsepower and 24 ft-lbs of torque; not a trivial amount by any means. In addition, we experienced a 1.2 mpg improvement in fuel mileage, which equals Flex-a-lite’s claim of 6%. The days of “free” diesel horsepower might be over, but with Flex-a-lite fans your truck can have more of the power and mileage that made you fall in love with diesel engines in the first place.
Fortunately, there are new and innovative ways to make more horsepower from your diesel truck without negatively affecting emissions. One of these methods isn’t really new at all; Flex-a-lite has been building radiators, electric cooling fans, and related cooling products for over 40 years, but until recently they did not offer anything specifically for diesel engines. Fortunately, they now offer direct replacement electric cooling fans for late model Ford, Chevy, and Dodge diesel trucks.
While modern fan clutch assemblies are more efficient than the direct drive mechanical cooling fans of old, they still take power to spin. This, in turn, reduces efficiency, which costs horsepower and mileage. Electric fans are typically lighter and more efficient than mechanical fans, but they have traditionally had two weaknesses: inability to keep up with the heavy loads diesel trucks are famous for; and custom fabrication for proper fitment. Flex-a-lite addressed both of these issues by integrating dual 15” S-blade fans that move a whopping 5500 cubic feet of air per minute (CFM) into a custom-fit aluminum shroud with applications for all popular late model diesel trucks. Other thoughtful features include a variable speed control depending on the load, air conditioning input, easily adjustable rheostat, and the ability to shut the fan off completely if needed.
Flex-a-lite claims an increase of as much as 27 horsepower, a 6% increase in mileage, and an installation time of four hours. Curious to put their claims to the test, we ordered up part# 262 for our 2002 Cummins-powered Dodge Ram. The first thing that caught our attention when we pulled the fans out of the well-padded box was what a masterpiece the TIG-welded shroud is. It is a shame to have to hide products this nice under the hood! Ford Power Strokes and Dodge Cummins use aluminum shrouds, while Chevy Duramaxes use an equally nice reinforced nylon injection molded shroud. All Flex-a-lite products are made in the USA, and our application included fan motors constructed by our neighbors to the north in Canada.
We went to Ken Imler Diesel Performance for the installation, who has installed dozens of these fans in the past. It took lead technician Steve Scott less than four hours with most of the time devoted to cleanly routing the included wiring and relays. Fit and finish of the shroud is perfect, including fitment of the coolant overflow tank and wiper fluid reservoir. Combined with the excellent instructions (Flex-a-lite includes detailed instructions, complete with illustrations. Can’t see enough detail in the black and white photos? Flex-a-lite has complete installation instructions on their website, complete with color photos that you can enlarge at the click of a button), it’s an easy day project for the home mechanic.
With the Flex-a-lite fans installed and wired, we put the Dodge on a Mustang Dynamometer to find out how much power we gained. The output of our Cummins increased by 14 peak horsepower and 24 ft-lbs of torque; not a trivial amount by any means. In addition, we experienced a 1.2 mpg improvement in fuel mileage, which equals Flex-a-lite’s claim of 6%. The days of “free” diesel horsepower might be over, but with Flex-a-lite fans your truck can have more of the power and mileage that made you fall in love with diesel engines in the first place.
 Fan Clutch: The stock fan clutch is much better than the mechanical fans of old, but it still leaves a lot of power on the table. These clutches can also wear out and fail to engage on high mileage engines, resulting in overheating problems. |
 Comparison: Out with the old, in with the new. The Flex-a-lite shroud is so good looking that the appearance alone is almost enough reason to change fans on your diesel truck. |
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 Circuit: In the middle of the control panel you can see the adjustment to set the temperature when the fans will turn on. These are set to 185 degrees from the factory, which we retained for our installation. |
 Motor: Flex-a-lite uses Canadian Unimotor components, which match the quality of the rest of the assembly. Each fan is capable of flowing over 2200 cfm of air, and unlike mechanical fans they are independent of engine speed. |
 Shroud: Flex-a-lite offers craftsmanship that looks like custom fabrication at prices we can all afford. The American-made quality really shows in the details. |
 Fan: One benefit of electric fans is that they allow the engine to get up to operating temperature sooner, and also cool down more quickly. This can be a real benefit in harsh climates. |
 Installed: Steve Scott added a wire loom to the fan wiring for a clean installation under the hood. The new fans are considerably lighter than the stock fan assembly, but weight is rarely much of a concern on a one-ton diesel truck. |
 Dyno: After the installation was complete, we strapped the Dodge to the dyno to quantify the gains. We were rewarded with an additional 14 peak horsepower and 24 ft-lbs of torque at the wheels. |
