In racing, the prevailing wisdom for enhancing a car’s cooling system was simple. The more rows you can put in a radiator, the better. But that advice is about as up to date as is, say, the notion of increasing horsepower by adding a “three-quarter cam,” whatever that is.
Cooling systems have advanced, and most of what we know about radiators — or thought we knew — also needs to evolve. We contacted Jeff “Fuzzy” Horton, technical director with C&R Racing Inc., a company that specializes in cooling systems for racing and military applications to see where the state of the art is today.
As we all know, setting up a production car for racing nearly always involves upgrading the cooling system. According to Horton, OEM cooling systems in general are only designed to handle peak BTU output a certain percentage of the time. When you take a street car and modify it for the track, a lot of times, the cooling system just can’t cope with it because the car is producing peak BTU most of the time.
It’s a balancing act to add the most capacity with the greatest amount of heat exchange capability for the water inside and the air passing through on the outside.
“Generally what we end up doing is putting more core in the same packaging area, which means sourcing a core that will fit in the same space claim to try to get more core in there, more water-to-cooling surface area,” Horton said.
One question that gets bandied about often is over which is better for cooling: cross flow or down flow? Well, Horton pointed out that C&R doesn’t have any data that shows whether a perfectly square radiator is more efficient with side or top tanks. That would be a true test, but most radiators are rectangular rather than square, which means that a cross flow is generally more efficient. Horton explained.
“It has to do with core surface area and how many tubes you can get in there,” he said. “If you have the width to put a cross flow in there and get more core to touch the air and have the tanks on either side, behind the core support, then you’re making a gain there.”
Surface area is important to the water inside a radiator and the air flowing through it on the outside. Tube design plays a big role as do fin design and louver design. Yes, those little fins between the radiator tubes also are punched with louvers. A lot of research has gone into this area of engine cooling, some of which contradicts the prevailing wisdom.
For example, say you have a 2-inch radiator and you have four half-inch tubes for a core. That would be considered a four row. Then say you have a 2-inch radiator with a single 2-inch tube as its core. That would be a single row. Which one would you go with? Conventional wisdom would suggest the four row, right? Not exactly.
“You’re going to have a tick more uninterrupted surface area and contact to the fins in the single 2-inch, which somebody would call a single row,” Horton said. “So that single 2-inch core is going to cool better than a four row with half-inch tubes in it. It would be hard to measure in a racecar, but in the stuff that we do when we’re designing cores or picking tube and fin combinations to use, we can see differences.”
In many instances, the solution actually is to add rows and fins to the radiator core, but that logic applies only up to a point.
“Typically, you’re trying to get as much water to touch that cooling surface and as much air to touch that same surface to pull that heat away, so if you start increasing one thing you have to balance with another,” Horton said. “At some point, if a vehicle is only capable of going 100 mph, eventually you’re going to pack so much stuff in there that even 100 mph air is not going to work. You need more air speed to push more air through there.”
That’s part of why major core suppliers have spent so much time and effort conducting research on core and fin designs, which can range from 13 per inch to as many as 22 per inch. Louver heights, the gap between each louver and the angle of each louver play a role. What that means to you as a racer is that you should pick up the phone and make a call before you blindly click and order whatever conventional wisdom suggests.
In terms of protecting your cooling system investment, Horton said the standard quarter-inch steel mesh grille is best for striking a balance between shielding the radiator from debris and still allowing enough air flow for proper cooling. Also, when you attempt to straighten the fins on your radiator that are bent over from debris impact, Horton recommends using restraint.
“Go through and clean it by blowing it out with compressed air from back to front instead of pushing the debris back in it. If the fins are laid over or the fins are bent from sand and rocks, and you try to straighten them out with a pick, just try not to go very deep into it,” he said. “Straightening those fins out and damaging the louvers isn’t as bad and the fins being closed up altogether or being clogged with debris. You just don’t want to go very deep into them.”