Cooling issue on highway
Don't let the facts get in the way of a good story:
- some years ago, Hayden or Flex-a-Lite or one of the fan companies had flow figures on their website. A 19" seven blade mech fan pulled 6000+ cfm. Have not seen an elec fan get close to that.
But at what RPM was that 6,000 CFM figure? Was it at idle? 3,000 RPM? 6,000 RPM? Clearly that matters. How much does that fan move at idle? Because idling in traffic with no air moving through the radiator other than what the fan is pulling is the worst case situation.
The Ford Contour fans on my Duster pull 3,500 cfm on low speed and can move 5,000 cfm on high speed. Which means my fans will move 5k cfm when I'm at idle at a dead stop.
99% of the time only the low speed on my fans is actuated. The only time the high speed on my fans has been activated is the few times when I was caught in traffic in 105°F+ temperatures, once when I was stuck in traffic for a good half hour in 110°F temps. Car never overheated. So I would argue that the majority of builds don't even need a 6,000 cfm fan.
However, there are NUMEROUS threads on this board about guys trying to run a standalone electric fan that moves less than 3,500 cfm, and complaining about not being able to keep the car cool. And that's my point about electric fans, because there are plenty of people that try to put together a stand alone electric fan system with a fan that doesn't move enough cfm to be a stand alone fan. Clearly in most situations my 3,500 cfm fans are enough, and depending on your build and driving habits some folks could probably get away with less. But there are some really expensive SPAL and other fans that only put out about 2,500 cfm which for a lot of builds will not be enough.
