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workingonit · #66 07-14-2021, 03:47 PM

Quote:

Originally Posted by X5chemist

Nice work. How do you plan to seal the fan edge to shroud? Closing the gap will increase efficiency. I've seen peeps use can foam to flat aluminum pieces.

Quote:

Originally Posted by workingonit

I'm sure that'd improve efficiency, but it's probably not needed. I bought a fan rated at 3000 cfm (Flex-A-Lite 238, puller) which should be overkill for a 225 hp straight-6. I used only 4000 cfm for my 427's, even on the street, in Texas summertime.

The gap in shroud coverage isn't any worse than some factory fans have, in my experience, and better than using no fan shroud at all.

Here are two old-school fan shrouds, one with tight blade fit and open corners, and another with inset blade coverage but no uncovered radiator surface. The first one relied on a mechanical fan, and max (bypass) airflow at highway speed was needed over the open areas for cooling. The second fan, also mechanical, had covered blades for safety, but total enclosure of the radiator surface might compromise airflow at highway speeds (depending on blade angle/speed and how tightly the surrounding fit was).

Second photo is a BMW aux fan, which uses a shroud with extra flaps that open to allow higher flow past it, at high speed, to cool the radiator/condenser better. With this fan/shroud already allowing some airflow in around the edges into the radiator, the new main fan really doesn't need to fill the radiator-side shroud so tightly, since airflow is coming thru at high speed anyway.

I've run many electric fans on many vehicles, and installed them on many more...about 1/4 without any shroud at all (for oil & trans cooler fans, farm tractors, supplementary A/C condenser fans, and some drag race cars); if there was a fan shroud already there, I modified/adapted it to fit the new electric fan, or just mounted the fan alone (usually added a pusher-helper on the other side). I never had one fail, or the vehicle overheat (except when the relay failed...I plan to carry a spare).

Nowhere in the fan literature that came with my new fan, did I find any mention of requiring a fan shroud; the fan manufacturers shape these aftermarket fan housings to promote airflow with no other help, but they usually also offer aftermarket shrouds as well. I've seen cars/trucks even recently come from the factory without real fan shrouds, just a framework for fan mounting. So, I think that by using the existing shroud on my X5, it will allow sufficient airflow at all speeds, so that tightening the gap around the slightly-inset 3000 cfm fan won't be necessary.

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