Keeping heat from overwhelming...
Keeping heat from overwhelming your engine can spell the difference between a good day and a bad day at the track.
Few things in a racer's life are more frustrating than a fast car that you cannot keep on the track for an entire race because of niggling mechanical problems. One of the most common examples of this is chronic engine overheating. You know the scenario: You're running great but notice that the water temperature needle keeps creeping steadily upward. You stand the chance of a good finish, but you can't afford to throw away engines like last week's newspaper, so once the needle pegs 250, you reluctantly bring the car in and watch the race finish just like the rest of the crowd.
When it comes to your engine cooling system, proper choices can help prevent this problem. A quality aluminum racing radiator is a remarkably efficient device, but if it isn't installed and used optimally, it can let you down. Here are a few tips for making the most of your old water box.
The radiator that provides...
The radiator that provides the best cooling for your needs may surprise you. What works best for the Nextel Cup guys isn't what's best for the Late Model racer on a half-mile track. That's why radiators such as C&R's Late Model radiator aren't just a stripped-down, cheaper version of what the Nextel Cup teams get; it is designed to meet different demands.
The greatest difference between a quality racing radiator and an off-the-shelf piece is how it was put together. A radiator works by providing the most efficient conduit possible, which is done by using the thinnest aluminum possible. This, however, makes it difficult to create a watertight seal. In the good ol' days, manufacturers had to use epoxy to seal the tubes to the tanks on either side of the radiator. Today, the best radiators are mainly sealed with TIG welds, and a process called brazing reinforces the seals. This provides not only a leak-proof radiator, but also one that produces the most efficient heat transfer possible.
"New technology radiator cores are made so that the tube-to-header bond is 100 percent, so epoxy isn't necessary," says Chas Howe of Howe Racing Enterprises. "This is done in most racing radiators with furnace brazing, which is where the aluminum radiator is heated to a near-molten state under a vacuum so that the fins, tubes, and header all bond and become one piece. This is a better way of doing things because the better contact you have between surfaces-especially between the tubes and the fins-the more heat is going to transfer from the water and into the air via the radiator."
A radiator with an integral...
A radiator with an integral heat exchanger will have a wide manifold on one side. This is an example of a Fluidyne unit with a separate oil cooler (top). With this design, the cooler is moveable and can be placed above or below the radiator, or anywhere else on the car as the racer sees fit.
The biggest decision to make when determining which radiator fits your needs is the thickness and fin count. For Saturday night racing, most manufacturers seem to prefer a two-row radiator with fins spaced to approximately 15 per inch. In applications where the height or width of a radiator is limited by framerails, manufacturers can run three or even four rows of tubes, one behind another. This allows more cooling for a smaller radiator, but the added thickness stalls the air as it moves through the radiator core. Keith Robertson of Fluidyne says his company only recommends a three-row radiator for high-speed tracks, generally a mile or greater in length. Otherwise, the incoming airflow just isn't strong enough to push its way through the radiator core effectively and provide efficient cooling. At high-speed tracks, the thicker radiators provide adequate cooling in a smaller area, allowing the team to tape off more of the grille.
An interesting side benefit of three- and four-row radiators, however, comes from the fact that it is difficult for air to move through them effectively. Air tends to "pile up" in front of the radiator core. The result is that less air makes it through the radiator into the engine compartment and is instead forced to flow up and over the car-providing more downforce.
Fin count works on much the same principle. More fins per inch allow more radiant cooling, but they also block air from moving through the core. If you are racing big, high-speed tracks, you likely will want to increase your fin density. If you race half-mile short tracks, your best bet is to stick to a density of 14-18 fins per inch. This will allow plenty of airflow through the radiator core and provide the best cooling for your needs.