Electric Fans

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Electric Fans

Postby brandon85 » November 1st, 2012, 12:10 pm

Do you spray the heads with water to cool? The only thing I have ever done is spray the heads with a 50/50 water/washer fluid mix(for the alcohol content).

Do any of you guys use fans to help cool the heads down? How effective are they? Do you use them with the car running or after you shut down in grid? What fans are the best. I have found a lot of 12v computer fans but I am concerned about longevity with all the heat from the engine.
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Re: Electric Fans

Postby bill_browne » November 1st, 2012, 1:27 pm

I did a lot of research when I decided to remove the alternator and fan. There's a very good article on the net about vw cooling, belt slipage, and fan speeds. What I got out of it is that max airflow out of a vw fan is about 700 cfm.

There are lots of automotive fans that will provide that kind of volume, but they are usually kinda big and spendy. Most of your standard 5" computer fans only put out 80 cfm. I found a 5" computer fan at a surplus place that moves 200 cfm. You'll believe it when you hear the thing run. :shock:

Originally, I cut the stock tins and rigged a fan on each side. Since then, I've built custom tins out of aluminum and use the stock bottom tins. If you'd like to see pics, let me know.

I leave the fans off until the head temp reaches 200. After my run, I kill the engine and let the fans run until the temp gets back down to 200, which usually takes 2 or 3 minutes. I have plans for a temp controller to do the fan switching, but that's in the future.

To help with longevity, I blow cool air down, not suck hot air up. This is my third season of using these fans and have had no failures so far.

I'm in Louisiana...August events are usually in the mid to upper 90's with high humidity. Course times run from 45 seconds to a minute 10.

HTH's
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Re: Electric Fans

Postby brandon85 » November 1st, 2012, 2:13 pm

How many CFM does the stock fan move at low rpm/idle? Pictures would be good. Do you run rear bodywork?

I never had a problem with just spraying the heads, but I want to make things easier. Keep the car from over heating if I get stuck in line before start on a hot day. And I, like you have serious hot summer in Memphis. Also spraying the heads worked for over 3 years but I would hate to crack something.
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Re: Electric Fans

Postby bill_browne » November 2nd, 2012, 10:33 am

Spraying water on hot metal gives me a bad gut feeling, and I always listen to my gut. But my gut has no connection to science or physics. :mrgreen: If it works for you, then I guess it works.

Here's the fan article: http://www.offroadvw.net/tech/wes/fan.html Either do to bad memory or looking at the wrong chart, it looks like I was low on max cfm, but the idle cfm looks to come in around 200.

Here's a couple of pics of my setup:
Image
Image

I made them so the top comes off with the fan, so I can change a fan without pulling the engine. As you can see, I can't do much to the engine without pulling it out of the car.

I usually run rear bodywork, but it has been off the car for the last 2 events for repair. Couldn't really tell you how that effects the engine temp.

The other thing I've done to help cooling a bit is to wrap the header pipes that run directly under the heads/cylinders. Some day I may add some ducting that gets air for the fans from outside the bodywork.

When I turn on the fans at 200 degrees, I can sit and idle all I want no matter how hot it is, and the temp will hold steady. Step on the gas, and the temp starts climbing.

One last note: I said that I can get the temp back down to 200 in just a few minutes. That's become a good thing. Our turn outs have been pretty thin lately. We click off the runs so fast, there's barely enough time to check tire pressures and get back in the car before your next run. We only had 25 entrys at our last event. I was afraid I'd have to skip some runs to allow for cooldown time. But it worked out good.

Good luck!
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Re: Electric Fans

Postby vreihen » November 2nd, 2012, 6:40 pm

I always thought that a gas-powered leaf blower would fit good on the empty generator stand on my Vee. Split the output with a Y hose to each side of the engine, set up a linkage from the throttle cable on the carb to control speeds, and give the F-500 guys a whiff of my own two-stroke oil when they're gridded behind me..... :twisted:
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Re: Electric Fans

Postby FM4SOLO » November 8th, 2012, 4:57 pm

I thought I might chime in, I was the co-driver of the Vee Brandon is talking about. I ran street bugs for many years. The heads got wet when driven in the rain, so I figured a little cool down spray wouldn't hurt them. Yeah, watching the stuff boil when you spray it kinda makes your stomach knot a little, but it worked.
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