This radiator includes the heat exchanger. Notice the extra volume and connections on the
Oil Coolers versus Heat Exchangers
If you are racing a high-output, dry-sump race engine, you probably need some form of additional oil cooling. If you need all the engine cooling you can get, a separate oil cooler is probably the best bet. This requires extra lines, extra space, and extra money. The second option is an integrated heat exchanger in the 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 radiator tubes.
"I think in most situations you would prefer the heat exchanger because it's more compact, there are fewer lines, and it's less prone to damage," Howe says. "I would recommend that to anyone running a good, professionally built dry-sump engine. If you are running an engine that is borderline on temperature already, the bad thing about cooling the oil through the water is, of course, it warms the water up. So it does take away some of the capacity of the radiator to cool the water if you are also trying to use it to cool the oil."
A third option is a product Howe Racing Enterprises produces called Cool Tube. It's a finned, solid tube that replaces braided oil line and helps cool the oil that passes through it. Cool Tube isn't designed to be a sole source of cooling, but it can be an effective supplement to your oil cooler or heat exchanger. Simply find a straight section along the route of your oil lines to the oil tank that gets a steady flow of cool air.
The number of cooling fins per inch is an important design decision. While more fins mean
Electric radiator fans are one of the few areas in racing in which the benefit of saving a few horsepower doesn't come at the cost of something else. A mechanical fan driven off the crank can burn as much as 20 hp at 6,500 rpm, which is definitely a significant amount. In short feature races, you can often get by with running an electric radiator fan completely off the battery, causing absolutely no horsepower drain on the engine. You often have the option of simply turning it off at race speeds when the incoming air flow is enough to provide adequate cooling on its own. In longer races, or in situations where you're running a few electrical devices such as blowers, you will need to use a belt-driven alternator to keep a charge in the battery, but the horsepower that a good racing alternator requires is still much less than a mechanical fan.
The downside, however, is that electric fans do not pull as much as a properly shrouded mechanical fan. If you are racing tight, short tracks with high-horsepower engines-especially in the southern United States-you may have no choice but to run a mechanical fan.
An old myth in racing was that the water pump needed a restrictor to slow the path of the water through the engine. The thinking was that if water traveled more slowly through the engine, it would be able to pull away more heat. That thinking is completely wrong on several levels.
"In a racing application, I haven't seen a case where you can move too much water," Howe says. "The big enemy of the cooling system is cavitation, which comes when the water pump has to work too hard. Anything you do to restrict water flow can lead to cavitation, which hurts the system's ability to cool because it generates air. Even in a closed system, a cavitating water pump has the ability to pull air from the water.
"The argument I always hear is, 'We slow down the water so it spends more time in the radiator.' But the cooling system is a closed system. If it is spending more time in the radiator, it's also spending more time in the engine, so it's a wash. There is really nothing being advanced by using a water restrictor. You are resisting against the water pump, and I've never seen any advantage to that."