| flex A Lite duel Fan
When it comes to automotive cooling fans, one thing is a given: The bigger they are, the more air they move - and the more horsepower they rob. Bigger fans require proportionately bigger fan clutches, which means that the fan in your truck could be turning as much as 90 percent of the shaft speed. You don't have to be a mechanical engineer to realize that that takes some serious horsepower away from your engine. But you can't take the fan off, so what can you do?
Flex-a-lite has the answer. For more than 36 years, the Milton, Washington-based company has offered a complete line of automotive cooling fans, oil and transmission coolers, and accessories. Roughly one year ago, Flex-a-lite introduced its model 270 electric cooling fan assembly for '97-'03 Ford F-150s, which includes Lightning and Harley-Davidson models, both supercharged and normally aspirated versions. According to Flex-a-lite, replacing the huge factory fan with the dual electric fan setup can increase horsepower between 12-15, and pick up torque by as much as 20 lb-ft at the rear wheels. That's a chunk! Plus, the company reports that the system increases water pump life because it no longer has a heavy clutch fan assembly hanging off it.
The model 270 uses a pair of 15-inch fans in an integral shroud that is a direct bolt-in replacement for the stock fan and shroud assembly. According to Flex-a-lite's Phil Hasenoehrl, the system is capable of pulling 5,500 cfm of air at 100 percent capacity, or about half of what the stock fan can pull. From the outset, this doesn't sound like good news, but consider this: Because the stock fan is engine-driven, it produces its peak airflow at high-rpm, full-throttle operation, where an engine spends very little of its time. Plus, under those conditions, the vehicle is usually moving fast enough where it doesn't need much help from the fan, if any. But where an engine can benefit from high airflow is when it is moving slowly, such as when you're stuck in that wonderful evening commute. Here, an electric fan setup holds a distinct advantage because it can be working at 100 percent capacity even when the engine isn't.
The model 270 operates via a variable speed control that references a thermister probe inserted between the fins of the radiator to determine coolant temperature. When you start the engine in the morning, the fans won't turn on until operating temperature is reached, which helps with warm-ups in cold climates. However, if you live in Arizona and the first thing you do when you key the engine is turn on the air conditioner, the fans will go to work immediately to make sure the cabin gets the coolest possible air from the air-conditioning system. At normal operating temperature (which can be set by the user from 160-240 degrees Fahrenheit) the variable speed control operates the fans at only 60 percent capacity, drawing as little as 12 amps. But when temperature rises 10 degrees, the fans kick up to 100 percent capacity and stay there until things cool back down. And when you park, the fans will stay on, helping to reduce heat soak.
To put the model 270 to the test, we brought an '02 supercharged Harley-Davidson F-150 over to Austin's Pro/Max in Tacoma, Washington, and put it on the company's Dynojet in-ground chassis dyno. Equipped with a pulley and some aftermarket exhaust mods, the truck laid down 341 hp at 4,200 rpm and 471 lb-ft of torque at 2,700 rpm to the rear wheels. We then drove over to Northwest Performance, also in Tacoma, and hung out while Loren Gordner expertly installed the model 270 kit. Then it was back to Austin's for some more dyno-flogging. The result was a gain of 10 hp at the same rpm and 20 lb-ft of torque 1,000 rpm higher in the engine's range; not the 12-15 hp Flex-a-lite claims, but to be fair, chassis dynos can vary several horsepower from shop to shop, depending on calibration, weather conditions, and so on. Aside from that, 10 hp and 20 lb-ft at the rear wheels are pretty decent gains for a product that can be installed in two hours by a competent wrench.
If you'd like to free up some emissions-legal horsepower from your Ford's engine, Flex-a-lite's model 270 is a great way to do it.
