Coolant flow

12many said
Don’t be a literalist. :poke::)Packing up, backing up, obstructing, impeding, blocking, restricting, whatever you wanna call it. I posted what I experienced with this Derale:

View attachment 1716086405It wasn’t cheap $$ that’s for sure. Flat plate shroud with high CFM fan. It didn’t take long for me to discover it had to go. You may have known this from the beginning of time, at the time I bought it I had to find an 18 inch fan with shroud that would fit my situation for dragracing and street use. For that it was fine, although I had to run it more than I care to. It was no good for Highway use in my application. And that style is what I am referring to which is the exact same thing you are referring to.

As to your assertion that I said a mechanical fan was “necessary“ maybe you have misread or perhaps you misinterpreted I don’t know, this is exactly what I stated:

Re-reading what I typed, it could be you are focusing on the part: “and/or” and perhaps I left out “or” between “blocking airflow, OR a good mechanical......” Was not implying having to use both, no sir. Perhaps I was not as specific and clear as I could have been. Grammatical errors happen.
Instead of seemingly looking to pounce and parse maybe try asking for clarity or simply give the benefit of doubt. No big deal. I know I need to sometimes so, anyway, have a nice evening
:)

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.

92b said
I said this in another post but the application can be what determines what fan does the best job.

The horsepower rating of the engine is not necessarily a good yardstick for what fan is needed. For example: You have an engine that makes 700 hp and you use that power for an occasional burst of acceleration then spend the rest of the time using 20 hp to cruise down the road or idling at a stop sign. Compare that to an engine that makes 400 horsepower that is being raced in a circle or on a road course that spends most of it's time making close to that 400 horsepower. The cooling needs of the two examples can be very different.

I think a better way to think of how much heat you need to extract is horsepower over time.

Electric fans have come a long way. They are more efficient than ever. But they move the same air if the motor is idling or at full load high rpm. Mechanical fans while not load sensitive are rpm sensitive. They move more air with increased rpm. They also have a power source that can power a large aggressive pitched fan blade. Try putting your hand in front of a radiator with an aggressive fan spinning 6000 rpm inside a good shroud. It moves alot of air.

Something to think about and I don't know the answer too. An aggressive pitched 4 blade mechanical fan can use 7 Hp. Assuming the fan efficiency was close to equal (maybe it isn't) how big would the motor on an electric fan need to be to move the same cfm that the mechanical fan is moving at 6000 rpm?

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.

dirty white boy said
wrong!! go do some research on cooling a dirt track car and you'll learn a thing or two!! go to a dirt track and walk around pits and ask some car owners if you doubt me!! electric fans been tried from high dollar aftermarket to ford 2 speed tarus/mini van fans and no body has yet to get them to work good nuff to run less the ambient temps are 65 degrees or cooler!! dirt racers would love to get red of there mechanical fans cause at race speeds that 30 hp thay could use else wheres, specially in the crate class's where each car got same exact 400 hp engine, thay'd pimp there mom out for a 20 hp advantage!! you can bet on that by god!! brought up cooling a dirt track car cause it takes a good system to get the job done! enjoy reading most of your post as thay are on point with good info, but im right on this, been there and done it, know it, spent good money to learn it!! got 4 crate model's setting here now!

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.