Fan conversion rambling

Mueller · Post by **Mueller** » Mon Jul 29, 2002 2:34 pm

Just thought some of you might like to see this...it's a fan conversion for a Corvair motor. The builder of the fan conversion claims that Porsche fan takes 12 HP @ 7,000 RPM while Corvair fan takes 27 HP @ only 6,000 RPM, so you free up 10hp with the 911 fan !!!
http://ebay1.ipixmedia.com/abc/M28/_EBA ... 3b/i-3.JPG

I guess we are not the only ones to use this fan setup.

Question: Has anyone made thier own upright fan conversion using a fan "other" than the 911 fan?
I was thinking that one could adapt a decent electric fan to mount on the alternator shaft and use that instead. It would be lighter and as long as it flows enough air, it would still cool the motor.

I really like the idea of the horizontal fan, but the extra parts needed to route the belt 90 degrees can add to more trouble than it's worth.

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Mike Mueller
'75 914 2.0

Chris_914 · Post by **Chris_914** » Mon Jul 29, 2002 3:53 pm

There are many issues that would have to be addressed using an electric fan cooling system for street use (variable speed control for proper cooling rate to load ratio). So I will make this as simple as possible. Do you know how big a 12HP electric motor is and how many amps it would take to run it? It would be rather large and heavy and (this is a guess since I don't have any specs available) would most likely draw at least 200-300 amps at 12V. Don't get me wrong, I like the idea but an electric system that would be at least as good as the factory or current conversions would have too many negative trade-offs.

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Chris
75 914 2.0L
72 1302s Super Beetle
71 Squareback
97 K2 Golf

[This message has been edited by Chris_914 (edited 07-29-2002).]

Mueller · Post by **Mueller** » Mon Jul 29, 2002 4:17 pm

I knew my post would be mis-interpeted

I meant to use just the fan portion of the electric fan and not use any of the electricals. The fan would be mounted to the alternator just like the 911 fan is.

By doing it this way, the cost would be cut significantly since you wouldn't need the 911 fan or alternator, in fact a GM single wire alternator could be used.

The plastic fan would be lighter than the 911 fan as well.

I guess I'll have to mock one up to see how feasible it would be and to show you what a mean.

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Mike Mueller
'75 914 2.0

Chris_914 · Post by **Chris_914** » Mon Jul 29, 2002 4:38 pm

aaaaaaaahhhhhh I see. Couple of issues to tackle. A plastic fan capable of moving the amount of air needed without flexing to much or just exploding. I think nissan or toyotas have a nice heavy plastic fan with short blades (2x0z and 240sx come to mind for the nissan). The other issue would be an alternator capable of supporting this type of load (the fan is going to add a new forward pulling force to the shaft) . All GM units I have seen have a nice bearing in the front but the back ones sucks even for their own intended purpose (more so with the later units). It also has to have a shaft long enough to mount the fan and pulley. A think a guy on the VW retail side was making some using I believe a rabbit alternator.

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Chris
75 914 2.0L
72 1302s Super Beetle
71 Squareback
97 K2 Golf

Mueller · Post by **Mueller** » Mon Jul 29, 2002 5:37 pm

One of the plastic fans I was looking at was a 16" diameter fan, at 2100 rpm it was rated at 2200 cfm.

According to Raby's site, the 911 fan pumps out nearly 3000 cfm of air, which is almost too much exept for a hot rodded Type IV motor.(this info from his site)

The two issues here are: can the fan move enough air at idle/low rpms to keep engine cool and can the fan stay together and not launch at higher rpms if it needs to be run at a higher rpm than listed.

I did not know that about the bearing issue with the GM alternator, thanks for the info.

Besides being cheap

I was looking at this option to save some weight as well as money....

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Mike Mueller
'75 914 2.0

[This message has been edited by Mueller (edited 07-29-2002).]

zydeco · Post by **zydeco** » Mon Jul 29, 2002 6:15 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mueller:
<B>One of the plastic fans I was looking at was a 16" diameter fan, at 2100 rpm it was rated at 2200 cfm.
</B><HR></BLOCKQUOTE>

Off the top of my head, the prosche conversion fan would run at around 10k-11k rpm at a sane crackshaft redline. So, with stock pully sizes, the 2100 rpm spec of that fan would lead me to believe that it can't handle the forces (or really even push any air even if it did stay together) at that fan rpm. You could come up with some creative pully ratios to underdrive the plastic fan but then you'd be running a few hundred rpm at idle - how much air would it push then?
Interesting ideas though - fans are usually more efficient at larger diameters and lower rpms. Hmmm?

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Brian
'73 Superbeetle

Tom Perso · Post by **Tom Perso** » Mon Jul 29, 2002 7:07 pm

How about putting one of those thermostatic clutches on the fan, just like on American V-8's?

Of course, getting the thermostat to work correctly for a ACVW motor might make things a little tricky.

Later,
Tom

Chris_914 · Post by **Chris_914** » Mon Jul 29, 2002 8:42 pm

I like the fan clutch idea! Now has anyone ever tried to "suck" the hot air from the engine to make the idea fuctional.

speedy57tub · Post by **speedy57tub** » Tue Jul 30, 2002 9:35 am

FYI, the 11-blade from a 2.0-2.4 flows 1634CFM at 4400rpm fan speed. You have to take into consideration your alternator-to-crank pulley ratio to determine the rpm of your own particular setup.

Regarding the alternators, the shaft bearing combination should be able to take both axial and radial loads. If the end castings physically permit, they can be machine to accomodate a set of bearings to address the axial and radial loading.

A gentleman in Australia (who already sells new 911 alternators with Bosch internals) is working on a 911 composite fan. I have not chatted with him in a while. If I hear from him, I'll post the infomation here.

Fan clutch idea...sounds good if it fits!

speedy57tub

IMPI · Post by **IMPI** » Tue Jul 30, 2002 10:34 am

The fan clutch idea was used on type 1 motors as anpower pulley alternative in the early seventies some old HotVW's magazines ran ads I dont remember the vendor.
As an alternative fan look into Magurius Deutz Big diesel aircooled engines and a bewildering amount of fans all looking similar to 911 fans. Dont know about availability in the US
regards
IMPI

CLKWRK · Post by **CLKWRK** » Tue Jul 30, 2002 12:02 pm

I thought the corvair crankshaft spun in the the opposite direction to a 911/VW, I wonder how they got the 911 fan to spin the right way. Am I wrong?.............BRY

maf 914 · Post by **maf 914** » Tue Jul 30, 2002 12:32 pm

Turn the fan around?

Mike

Mueller · Post by **Mueller** » Tue Jul 30, 2002 12:39 pm

The corvair engine must be run backwards with the 911 fan conversion. I don't see him selling too many of these conversions due to that, but he might.

Racer Chris · Post by **Racer Chris** » Tue Jul 30, 2002 3:46 pm

So far I have been extremely pleased with the corvair fan setup on my 914 race car. The fan is trimmed down to fit on the T-4 crankcase, under a custom fiberglass shroud. The 90 degree bend in the belt has not been a problem with NAPA belts, up to 8000rpm. My current engine runs at 350F head temps in 80+ deg. weather, WOT. I am pretty sure it's consuming less than 12hp.

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Chris F.

www.tangerineracing.com

turboteener · Post by **turboteener** » Tue Jul 30, 2002 4:26 pm

Chris something I thought about for my GT3 car was pulling air through a duct either in the drivers compartment or under the car and through the engine and then venting the air out the trunk lid. TO create an aerodynamic advantage. The rule book nixed that idea in a hurry.

I do know of a nationally competetive GTU 914-4 that ran a cooling system based on two electric squirrel cage fans. The alternator ran off the drive axle. His motor made 220 hp@7800.

Chris_914: "I like the fan clutch idea! Now has anyone ever tried to "suck" the hot air from the engine to make the idea fuctional."