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914World.com _ 914World Garage _ Engine Cooling Flaps

Posted by: BMartin914 Sep 1 2005, 11:12 PM

I am putting the final touches on my engine after having it apart for some time. I can't recall which position the cooling flaps should be in for full closed when cold.

Should the thermostat wire be pulling on the flaps when cold and then expand to allow them to open (putting the attaching point in the upright position when warm) or does the wire pull the flaps open as it expands?

Might sound like a dumb question to some, but I can't quite understand how they flow - hot vs. cold.

Posted by: Cap'n Krusty Sep 1 2005, 11:19 PM

The coil spring holds the flaps in the open position, as it would be hot. Think of it as a default setting. The top of the shaft is rotated fully toward the shroud, away from the crankcase. Got the picture? The Cap'n

Posted by: MarkV Sep 2 2005, 12:44 AM

I am in the same boat. Took it apart in November, trying to get it put back in this weekend.

Please clarify for me. Is the photo below "COLD"? Drivers side flap closed, passenger side flap open exposing the oil cooler.

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Posted by: MarkV Sep 2 2005, 12:48 AM

Is the phot below the "HOT" setting? Drivers side open & passenger side oil cooler blocked.

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Posted by: MarkV Sep 2 2005, 01:17 AM

There is a classic thread on the subject.

However, the photos are confusing. The first photo is labeled "closed for cooling" and the second photo is labeled "open for cooling". Which is it, are the flaps open for cooling or closed for cooling?

http://www.914world.com/bbs2/index.php?act=ST&f=5&t=30107&st=0

Posted by: BMartin914 Sep 2 2005, 07:20 AM

The classic thread is helpful, but I agree it is a bit confusing.

I think that the most valuable tidbit I took from it is that the flaps are designed to be in the "full open" position if the wire were to break. So basically, the spring has no tension on it when hot and as it cools back down, the bellows pull the flaps closed.

I think I have got it now. It also makes it a bit tough when you cannot see the flaps, only what is above the tin.

Posted by: maf914 Sep 2 2005, 08:23 AM

The top photo is the COLD position and the bottom is the HOT position. The flap at the oil cooler is open when the engine is cold to allow the air to bypass the cooler so that the engine oil can heat up faster. When hot the trailing edge of the flap closes on the trailing edge of the cooler directing air through the oil cooler core to cool the oil. This is the position the flaps should be in if there were no thermostat and cable attached.

The left flap in the photos never does close off the airflow completely, but I think it does adjust the volume on that side of the engine. I'm not sure but I think it acts as a volume damper to balance the airflow with the flap on the right. I wonder how long the VW designers took to come up with this system?

Posted by: SirAndy Sep 2 2005, 10:49 AM

QUOTE (maf914 @ Sep 2 2005, 07:23 AM)
This is the position the flaps should be in if there were no thermostat and cable attached.

you get max. cooling when the right flap covers the oil cooler as it allows a full air-stream to go through the cooler, thus. max cooling.

this is where the flaps should be when the engine is warmed up ...
Andy

Posted by: URY914 Sep 2 2005, 10:56 AM

Now lets say you have a a/x only car.

Do you run flaps but no cable and 'stat?

Or no flaps at all?

Posted by: SirAndy Sep 2 2005, 11:01 AM

QUOTE (URY914 @ Sep 2 2005, 09:56 AM)
Now lets say you have a a/x only car.
Do you run flaps but no cable and 'stat?
Or no flaps at all?

depends on how you get the car to the AX and back ...

we have guys here that run no cooling/engine tin, no fan or fan housing, no alternator, no starter, nada ...

just the bare block and a tiny computer fan on top of the oil cooler held down by a rubber band ...

you'll need a support crew to push-start you before every run and you shut it off as soon as you come off the course, no cruising around in the paddock ...

the car usually takes TTOD when he shows up ...
Andy

Posted by: Aaron Cox Sep 2 2005, 11:04 AM

i run no T stat, just let the car idle longer before you drive it...

slower warm up...

Posted by: maf914 Sep 2 2005, 11:07 AM

Paul, I'd say check with your engine builder.

Now for lightness you may want to form some flaps from carbon fiber. And maybe drill some holes in them.

Posted by: URY914 Sep 2 2005, 11:08 AM

QUOTE (SirAndy @ Sep 2 2005, 09:01 AM)
we have guys here that run no cooling/engine tin, no fan or fan housing, no alternator, no starter, nada ...

just the bare block and a tiny computer fan on top of the oil cooler held down by a rubber band ...

No thanks, not around here when it's about 110 drgrees on the asphalt. I'll run a fan with a few blades missing and the engine tin trimed back to just what I need.

But I think you gotta blow some real air over those heads.

And having on starter must be a PITA.

P

Posted by: SirAndy Sep 2 2005, 11:57 AM

QUOTE (URY914 @ Sep 2 2005, 10:08 AM)
And having on starter must be a PITA.

not really, he always has a 4-6 man pit-crew with him ...

Andy

Posted by: Elliot Cannon Sep 2 2005, 12:16 PM

QUOTE (Aaron Cox @ Sep 2 2005, 10:04 AM)
i run no T stat, just let the car idle longer before you drive it...

slower warm up... ;)

With no Tstat it takes much longer to warm the engine at idle. Then you have an engine running at a longer period of time that is not at operating temp. Not good. The idea is to warm it up quickly, then keep it cool.
Cheers, Elliot

Posted by: rhodyguy Sep 2 2005, 10:45 PM

warm and cold is a better discription than open and closed. here is the cold position. both sides raise as the thermostat relaxes and the spring on the cross bar does its job.

k

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Posted by: rhodyguy Sep 2 2005, 10:48 PM

perhaps of some interest. the drivers side is never fully closed off while cold. the little stop keeps it open to some degree, at all times.

k

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Posted by: rhodyguy Sep 2 2005, 10:54 PM

damn. i guess i have to take off the flaps and cross bar to paint them. this is when i all starts to go south. wait!! no one can see them when all the tin is on!

k

Posted by: brant Sep 2 2005, 11:03 PM

the last couple of -4 motors I had came back from my builder with sheetmetal screws holding the flaps into the hot position....

of course it was a trailered car at that point.

brant

Posted by: rhodyguy Sep 3 2005, 08:42 AM

i can't imagine a worse situtation with a slower warm up and carbs arron.

k