Coolant flow

72bluNblu said
That may not be a cheap fan cost-wise, but as you found out it's completely inadequate. The fan shroud is just a cookie sheet, not a piece that was designed for air flow. And the fan itself is only rated for half of what you'd need to cool that engine, if that.

Buying an expensive aftermarket fan does not guarantee success. You need to make sure it can put out enough CFM for your application, and it has to be designed to work with its shroud to flow air. The Ford Contour electric fan set up I run costs significantly less than that DeRale, and flows twice as much air.

Your RPM example is exactly why mechanical fans are inefficient. The fan has to do the most work at idle, when a mechanical fan is turning the slowest. At higher engine rpm's the car is MOVING, which means your airflow is coming from the speed of the car, not the fan. You don't even need the fan to be spinning at all once you're doing 25mph or more. The electric fan always spinning the same speed is an advantage, it can flow the most air when the engine is at idle and the car is sitting still, which is exactly when you need the fan to be doing the most work.

And yes, I am very familiar with how much air a mechanical fan can move. Which is why I picked an electric fan that can move just as much. If you've ever seen a Contour fan set up running at high speed, you'd know it moves just as much, if not more, than the mechanical fans these cars came with. Especially if the engine is just idling.

I don't need to do any research on cooling a dirt car, there are electric fans more than capable of cooling those engines. But as you said, the class of racing you're talking about doesn't run alternators. An electric fan that would cool those engines needs to be supplied with 40+ amps of power to deliver their rated CFM. This just goes back to the basic mistakes people make when choosing electric fans- they don't pick a fan with enough CFM, they don't wire it with the heavy duty wiring and relays needed to supply the power they need, and they don't run a power source capable of feeding the right amount of power to the fans when they're running.

I have no issues cooling my 400+ hp, all iron 340 with the electric fans I run. They never even come on when my car is moving more than 25 mph, and they've cooled it just fine when it was 110° out and I was stuck in traffic. That's a harder ask than anything a dirt car with 400 hp requires.

Your street car and my circle track car are polar opposites when it comes to cooling system requirements. But for the sake of this discussion let's say that what they have in common is that they both have motors that make 400 horsepower. That is the point I was making in the post. Different applications require different cooling systems including fans.
You said your street car needs to move the most air at idle. The only time my circle track car is idling is when it is in the pit warming up for the race. If it's cool out I have to put cardboard in front of the radiator to even get the needle to come off the peg on the temp gauge. There is no load on the engine at idle so there is very little heat that is produced by the engine and the fan on my racecar even at idle speed is overkill. Is that fan inefficient at idle? Absolutely. But that big (overkill at idle) fan is going to have it's hands full when the car is at speed on the racetrack. Because it is under a heavy load the entire time it's on the race track with no break. Except for an occasional caution flag.
You said your car doesn't even need a fan above 25 mph . The air flow through the grill is sufficient to cool the car. That's because your car's engine has very little load on it to propel itself down the highway. My circle track car has air going through the grill too. It also has an air dam below the radiator to pick up even more air. And that's not anywhere close to enough air to keep the motor cool with out the additional air provided by the fan at 6000+ rpm. It wouldn't make it two laps without a fan and the gauge will be pegged. Due to the continuous high load on the engine.
I'm not saying one fan is better than the other, electric or mechanical. Each has their advantages. I'm saying different applications may require different types of fans.
Put a hitch on your car and hook a 10,000 pound trailer to it. There is a chance your.cooling system requirements might change. Different application, different cooling system requirements.