I contacted Chris Paulsen at C&R Racing, racing radiator manufacturer. He does a lot of their research and testing. First I asked Paulsen about water flow speeds in the radiator system.
On the left is an aluminum...
On the left is an aluminum high-volume racing pump. The one on the rightis a stock iron pump. Racing iron pumps are available where rulesrequire iron. A 24 to 28-pound radiator cap will retard pump cavitationand keep coolant flowing.
"You really need to move the water as fast as possible," Paulsen says. "Some old thinking is that water speed needs to be slow so it has more time to transfer heat. In (our) testing this has been proven to not be the case. If the water is moved faster it becomes a turbulent flow. This allows it to transfer heat at a faster rate."
Paulsen says a restrictor should still be used in the thermostat housing, not to slow the water, but to build pressure in the block to prevent steam pockets. The higher the volume of the pump, the less restrictor is needed. This is because the high- volume pump is pressurizing the block. In doing so, more water is allowed to flow through the radiator.
"Radiator design is a great factor in cooling systems," Paulsen says. "Our testing shows that using two one-inch tubes provides better heat transfer than four half-inch-wide tubes. The reason is this: The water flow area of both designs can be the same. However, the two-tube design has more brazed fin contact with the tube. Heat is transferred from the tube to the fin, then to the air. So more fin contact with the tube leads to more efficient cooling. The four-tube designs work well but need a little more radiator area."
Electric fans, such as this...
Electric fans, such as this one from Flex-a-lite, have some racingapplications but the electricity used to drive the fan comes from thealternator, which gets its power from the engine. Electrics are good forthe tow vehicle because their power switch can be thermostaticallycontrolled; they aren't running all the time. This is a fuel saver.
Paulsen says his research into fin count also pre-empts some old thinking. "Fewer fins have less contact area with both the tubes and the air," he says. "We see the low-fin-count radiator stop up as much as the high fin-count. With a lower fin-count, debris is only embedded deeper in the fins, making it more difficult to see and clean. Every effort should be made to keep dirt, etc., from reaching the radiator. On short dirt tracks, this may mean blanking off the direct ram air entry to the radiator (maybe a plastic nose piece) and letting the fan do the work."
Water Pumps And Fans
Howard Stewart of water pump fame answered several questions for us about water flow and airflow.