An efficient cooling system...
An efficient cooling system not only keeps your expensive race engine healthy, but it can also offer a competitive advantage. For example, a mechanical fan robs horsepower from the engine, so any time you can run an electric fan like you see here and still keep your engine cool enough, you’re sending a few extra horsepower straight to the rear wheels.
You can’t make horsepower in an internal combustion engine without burning gasoline. And the byproduct, of course, is heat. We all know what to do with the power generated, but the heat is something else.
If the heat generated by the combustion of gasoline isn’t controlled, you’ll wind up with detonation, the engine oil will break down which will lead to lubrication problems, and other bad (not to mention expensive) things will happen. Plus, the more power you’re making, typically the more fuel you’re burning, so heat control becomes even more of a factor.
Fortunately, proper engine cooling systems are more than capable of handling the heat created by your race motor. The trick is to choose the best radiator that will work for your situation and maintain it properly so that it performs just as well at the end of the season as the day you bought it.
High-performance aluminum radiators have been the standard in racing for years now. They are significantly better than stock-style radiators that were made of copper and soldered together. Aluminum construction creates a radiator that can shed heat better than practically any other material.
But there’s more to it than simply making a radiator out of aluminum. PWR Performance Products has only been a part of stock car racing in the United States for a few years, but the Australian radiator manufacturer is already used by approximately half of the teams in NASCAR’s Sprint Cup Series. The company has been welcomed by many of NASCAR’s top teams because it can custom-build radiators to any size. As a longtime builder for several Formula 1 teams, it has been bringing several new features to the table for stock car racing.
Cooling fins are the thin...
Cooling fins are the thin strips of aluminum that form an almost corrugated construction between the cooling tubes in your radiator core. For most Saturday night tracks less than 5⁄8-mile, a relatively light fin density of 15 fins per inch normally works best. Higher speed tracks can use a radiator with a greater fin density because the greater speed helps push the air through the more congested radiator core.
Thanks to that success, PWR has recently begun a brand-new product line of radiators for Saturday night racers. These radiators will be completely made in the USA and designed specifically for the needs of racers competing on the bullrings all across America.
These won’t have all the bells and whistles that the radiators the Cup guys are running have, but PWR’s Justin Raybourn and John Dullam—the domestic arm of the company—say that many of the features that work well for the high-speed Cup cars won’t be beneficial to short track racers. For example, Saturday night racers normally see slower speeds and tighter traffic, so their radiators need a lower fin count to allow air to move through the radiator core more easily.
“Cup teams are also running pressurized cooling systems and require a radiator that can handle coolant pressures over 200 psi,” Raybourn adds. “That’s just not necessary on a Saturday night car, and building that kind of capability into a radiator is, honestly, a bit expensive. So by being smart about how our Street and Racer series of radiators are built to the customer’s needs we can provide a very high-quality radiator at a reasonable price.”
A radiator’s thermal efficiency, or how quickly it can pull heat out of the coolant flowing through it and radiate it into the air, can be improved by maximizing the surface area of the tubes the coolant is flowing through. To do this the tubes are wide by very thin vertically. Picture a drinking straw pressed nearly flat. This means that almost all the water flowing through the tube is actually in contact with the tube itself, which improves heat transfer. Then, in order to move the heat from the tube to the fins and the atmosphere beyond it, the wall thickness of the tubing is also minimized as much as possible.
To help increase cooling efficiency...
To help increase cooling efficiency even more, some high-quality manufacturers can actually put louvers in the cooling fins, like this sample you see from PWR.
As this story went to press,...
As this story went to press, PWR was still putting the final touches on its line of affordable “Street and Racer series” of radiators. They didn’t have a race-specific radiator ready to show us but said this street-oriented radiator is very close (minus the fittings for the heat exchanger). This appears to be a high-quality, single-row radiator that will be an excellent choice in many different racing applications.
The billet aluminum filler...
The billet aluminum filler neck has plenty of material right where it’s needed and is a design feature that has made its way down from the high-dollar custom radiators PWR produces for the NASCAR Cup teams.
But doing this also makes it difficult to properly seal the radiator from leaks. The old school method was to use epoxy to seal the tubes to the tanks on either side of the radiator. But epoxy works as an insulator, which keeps the radiator from working as efficiently as possible. Today, most high-quality radiators use a brazing method to seal the joints.
According to Raybourn, PWR actually uses an ingenious method to braze its radiators without harming its efficiency when it comes to cooling the engine. The aluminum radiator tubes actually feature two different materials. The inner portion of the tube is made from high-strength aluminum with a high melting point. But the outer 10 percent of the tubing (approximately) is clad with a different aluminum alloy that is also very good at transferring heat but has a lower melting point.
Once the radiator is assembled, it’s heated to a temperature that’s high enough to melt the aluminum cladding on the outside of the tubes but not the main alloy. This brazes the radiator into one functional piece, which eliminates leaks without harming the piece’s ability to remove heat from the cooling system.
Here’s a shot of the clad...
Here’s a shot of the clad aluminum cooling tubes. In the foreground is a typical tube from the Street and Racer Series. In the background is a Cup-style cooling tube that may someday make its way down to the Saturday night levels. Notice the dimples in the tube; they’re designed to help create turbulence in the coolant as it passes by so more of it comes into contact with the walls of the tubing.
Two of the biggest decisions to make when determining what radiator best fits your needs is thickness and fin count. For Saturday night racing, a single- or double-row radiator with a lower fin count seems to work best. Dullam points out that for a radiator to do its job, the most air possible has to flow through the core.
A radiator that has the coolant tubes and cooling fins packed too tightly will actually block air from moving through it. But more fins offer more surface area, so finding the right balance is critical. Dullam says Cup cars normally use a fin count in the range of 20 per inch because their higher on-track speeds create higher air pressures in front of the radiator to force the air through. But for the tight racetracks that Saturday night racers normally compete on, a lower fin count works better.
Normally, a radiator design with around 15 fins per inch works best. It provides plenty of surface area to move the heat from the radiator to the air moving through the core while still being open enough to allow plenty of air to flow through.
In applications where the height or width of the radiator is limited by the framerails, you may choose to go with a two-row radiator. This style places a second row of cooling tubes right behind the first. This allows for more cooling in a smaller radiator, but the extra thickness a second row creates can also stall the air as it moves through the radiator core. There are even three-row radiators, but you should only consider one of these on very high speed tracks, typically a mile or more.
Oil Coolers and Heat Exchangers
PWR is also bringing to the...
PWR is also bringing to the U.S. a line of affordable but high-quality gear oil coolers made specifically to handle the higher viscosities of oil.
If you’re racing a high-horsepower, dry-sump engine, or you’re doing a lot of shifting and having transmission issues, you may need to consider additional cooling beyond a typical radiator. If you need all the engine cooling you can get, or need to find a way to get the oil temps in your transmission down, a separate oil cooler may be necessary. This requires extra lines, extra space, and extra money.
Another option is an integrated heat exchanger that’s part of your radiator. It functions by routing the oil lines through the radiator manifold. The heat from the engine oil is passed to the water and eventually to the air as the water flows through the cooling tubes.
One caveat with running a heat exchanger is that the oil provides an additional heat source for the coolant. So if you’re running a heat exchanger to cool your transmission oil, be aware that it will reduce the radiator’s ability to control the engine temps. This may require a larger radiator than you used previously.
While working on this article...
While working on this article we also stopped by the chassis building shop of Leavitt Racing Components where fabricator Bob Newling was putting a new front clip on an asphalt car. We thought his method for mounting the radiator was simple, lightweight, and sturdy and he said we were welcome to share it with you.
The first step is to weld...
The first step is to weld a butt plate on the end of the front clip. Right now it’s only tacked into place, but Newling will weld it fully before moving on to the next step.
Next, Newling uses clamps...
Next, Newling uses clamps and a piece of plate steel to clamp an approximately 4-inch frame horn to the butt plate. The frame is flush with the outside edge of the tubing for the front clip and on the same angle. Also notice that the seam is on the inside. By mounting the seam on the inside on both sides of the clip, it will help the bumper and anything else mounted to it collapse inward to help protect the driver.