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Re: Magnesium Fans
Posted by: American Mel ()
Date: February 10, 2018 06:38PM

MattNall Wrote:
> Always wondered if that actually helps...
> Maybe Kevin can rig one up on his test rig!!

That would be a GREAT idea! thumbs up
Personally, I have my doubts that it would make even a measurable difference at that height.
I am no aerodynamics engineer by any means, but I would think that it would need to be closer to 4 inches tall to really be effective.
I would also model the shape after the center cone in a Jet-turbine engine, not such a sharp point.
I can't imagine they just stuck those nice rounded cones in there and said "Awhh, tha's gud nuff!"

BUT, while he has not spoken about it, it appears that Kevin has also been working on the pulley too! If you look closely in the photo, there appear to be angled air flow holes in the sides of his pulley!
Maybe he will tell us more about it in his thread?
Since this thread is actually about disintegrating Mag fans.eye rolling smiley

WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
'66 Monza Coupe - 4spd, 140 Daily driver beater
'67 Monza Vert. - PG, 140 Daily driver beater

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Re: Magnesium Fans
Posted by: 63turbo ()
Date: February 10, 2018 08:22PM

Mel is right, that cone doesn't do much of anything because it is way too short, and the actual airflow path is tipped over a lot! Mel- you've got sharp
eyes, nobody else has asked anything about those holes in the pulley. I talked about doing something like that on Fastvair a few years ago, and a bunch of people that should have known better pretty much laughed it off, saying it wouldn't work/wouldn't help much. Fluid Dynamics was one of my best subjects in
College.... somebody was wrong here, and I was SURE it wasn't me!!
anyways, I went ahead and figured out how to calculate how much velocity pressure was lost by the pulley, and it was suprising to me how big the losses
really were, compared to a pulley that was opened as much as could be done.
Here's the estimated gain in pressure vs engine rpm. At 4k: 2.13"
5k: 3.33"
6k: 4.8"

The reason this works is that the o.d. of the pulley is roughly 30% of the
total area of the opening, and more normal opening vs pulley area might only be
9 to 10 % when sized for a belt driven fan. The losses for something like that are very minimal, but when it gets to 30% of the opening, the loss is TEN TIMES
bigger, and isn't insignificant anymore.
Yes, the openings in the pulley really did increase the flow, and, at least with my fan seemed to increase the efficiency, the bugger is that it needs to have a bell on to work. The bell helps the pulley, the pulley helps the bell.


Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: []
first test start on EFI here:[]
first official EFI boost test here:[]
My new fan! []
engine less 62 Spyder
Canadian 64 Monza Parts car

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