 What do these air flaps do?, And how important are they? |
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| JeffBowlsby |
 Dec 15 2005, 01:51 PM
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#1
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914 Wiring Harnesses  Group: Members Posts: 8,511 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None 
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I bet most 914s don’t have these flaps anymore. These hinged flaps in the diagram are called ‘engine fan flaps’ or ‘non-return flaps’ in the parts manual. They close off the supply air duct path from the engine fan to the heat exchangers when the engine is off by gravity. They open up with the force of supply air to the heat exchangers when the engine is spinning, to circulate air through the HEs into the cabin, as assisted by the electric blower fan in the engine bay.
So the only thing I can figure is that after the car is hot and the engine is shut off, the flaps close to prevent hot air from entering the supply air fan plenum…but I can’t figure out why that’s important. Any ideas? Attached image(s) 
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Replies(1 - 19)
| bd1308 |
Dec 15 2005, 01:54 PM
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#2
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
they're real flimsy tin pieces....mine actually fell off at one point in time when my heating system was not connected.
b |
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| Demick |
Dec 15 2005, 02:01 PM
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#3
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Ernie made me do it! Group: Benefactors Posts: 2,312 Joined: 6-February 03 From: Pleasanton, CA Member No.: 257  |
I believe the purpose of those flaps is so that when the heater blower is on, and the engine is at idle, the heater blower can overpower the main cooling fan and blow hot air backward from the heat exchangers into the main fan area - resulting in warmer air being used to cool the motor.
With the flaps, under this condition, the flaps will close not allowing this backward flow of air. When the engine speed is raised so that there is more pressure from the engine fan than from the heater blower, the flaps open. Demick |
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| Bleyseng |
Dec 15 2005, 04:00 PM
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#4
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)
Yup Demick nailed it! $25 each these days from AA. |
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| SLITS |
Dec 15 2005, 04:17 PM
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#5
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
And the assumption is your HEs are not swiss cheese either. |
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| SirAndy |
Dec 15 2005, 04:30 PM
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#6
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Resident German Group: Admin Posts: 41,651 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) |
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| McMark |
Dec 15 2005, 04:34 PM
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#7
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
Nice description Demick. (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)
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| bd1308 |
Dec 15 2005, 06:16 PM
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#8
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
i'll just make some from aluminum sheet metal.
b |
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| ClayPerrine |
Dec 15 2005, 06:21 PM
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#9
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Life's been good to me so far..... Group: Admin Posts: 15,474 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille
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Actually... its all a gag being played on everyone who owns a Type IV powered car.
Like the round holes with the plugs in the body, they are there to make you ask (IMG:http://www.914world.com/bbs2/html/emoticons/WTF.gif) |
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| IronHillRestorations |
Dec 15 2005, 08:39 PM
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#10
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I. I. R. C. Group: Members Posts: 6,719 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None
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I thought those were for primer paint flow, ie dipping the chassis at the factory, but that's just a guess. |
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| joeav8tor |
Dec 15 2005, 10:26 PM
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#11
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Member Group: Members Posts: 408 Joined: 23-January 05 From: mattituck, Long Island NY Member No.: 3,493 |
the flaps also work opposite of each other...the flap over the oil cooler is open when the engine is cold , while the other flap on the other side is closed...as the engine warms up, the thermostat expands opening the flap on the side with the number 1 cylinder, while closing the flap over the oil cooler, allowing the air to flow through the cooler. (IMG:http://www.914world.com/bbs2/html/emoticons/flag.gif)
Joe |
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| John |
Dec 15 2005, 10:33 PM
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#12
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member? what's a member? Group: Members Posts: 3,393 Joined: 30-January 04 From: Evansville, IN (SIRPCA) Member No.: 1,615 Region Association: None |
I swear those are aluminum with a foam rubber gasket glued to it (them).
I'll sell some for $24.95 each.......... (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) |
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| scruz914 |
Dec 16 2005, 01:34 AM
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#13
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Senior Member Group: Members Posts: 815 Joined: 26-February 04 From: Santa Cruz, CA Member No.: 1,724 |
Although I am sure you are correct, I find it hard to believe that the wimpy heater blower has enough power to overpower the flow of the cooling fan, even at idle. When I took the heater tubes off one of the flaps was missing and one was sitting in the tube off its hinge. I was considering just leaving them out but now maybe I'll clean the one up and fabricate another and put them back in. -Jeff |
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| joeav8tor |
Dec 16 2005, 07:08 AM
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#14
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Member Group: Members Posts: 408 Joined: 23-January 05 From: mattituck, Long Island NY Member No.: 3,493 |
I dont think the heat has anything to do with the operation, or engineering of the flaps...when the engine is cold, the flap above the oil cooler is open, allowing the air to pass over the oil cooler, thus the warm oil is being circulated through the cooler allowing the engine to warm up more quickly...after the engine heats up, the thermostat expands, closing the flap over the oil cooler, redirecting the air to go through the cooler to aid in cooling the oil...I inspected mine when I dropped the engine for a tune up, and seals. There has been a thread on this in the past, Brad Roberts also explained it very well...either way, I think it is a good idea for the system to work, and so did the German engineers that came up with it...good luck, Happy Holidays (IMG:http://www.914world.com/bbs2/html/emoticons/flag.gif)
Joe |
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| DJsRepS |
Dec 16 2005, 07:32 AM
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#15
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Member Group: Members Posts: 431 Joined: 4-November 04 From: Sarasota Florida Member No.: 3,060 |
Finally bingo Joeav8tor. They are hooked by cable and pully to a Tstat that works simular to a tstat of a water cooled car. They preheat motor then regulate temp thats all.
I live in fla and removed the whole assy and even the heater. Mine was not working cable off pully and jammed shut over heating motor. Attached image(s) 
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| JeffBowlsby |
Dec 16 2005, 08:34 AM
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#16
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914 Wiring Harnesses Group: Members Posts: 8,511 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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Joe/DJ...
We are talking about the lower flaps...not the upper flaps. See the diagram in the first post... |
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| Bleyseng |
Dec 16 2005, 08:54 AM
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#17
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
(IMG:http://www.914world.com/bbs2/html/emoticons/hijacked.gif)
The upper cooling flaps should jam open if the cable breaks or the thermostat fails so there is no way it will overheat the engine. (IMG:http://www.914world.com/bbs2/html/emoticons/chair.gif) |
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| double-a |
Dec 16 2005, 09:31 AM
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#18
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Senior Member Group: Members Posts: 987 Joined: 15-September 03 From: vancouver, wa, usa Member No.: 1,162 Region Association: Pacific Northwest |
last time i was under there i noticed the starboard side flap was missing. since the system had never been taken apart prior to my tinkering, i can only assume that flap is still hangin around in there somewhere.
~a |
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| joeav8tor |
Dec 16 2005, 12:37 PM
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#19
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Member Group: Members Posts: 408 Joined: 23-January 05 From: mattituck, Long Island NY Member No.: 3,493 |
sorry about that, I saw the beginning diagram, I still have the flaps on my 2.0 which are free to open and close by forced air....Joe
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| VWnDRAG |
Dec 16 2005, 05:47 PM
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#20
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Member Group: Members Posts: 69 Joined: 23-September 05 From: Hollywood, CA Member No.: 4,850 |
Those little post-fan, gravity close, tin flaps right? I asked the same thing at my first engine pull party. Being a newbie, I either got the correct answer from a couple guys “in the know” or, everyone had a good laugh when I left.
* (see Snipe Hunting) (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif) The reason for the flap is to keep mice from getting into the engine compartment. Supposedly the VW/Porsche engineers could foresee mice nesting in the fan housing. I guess it’s a bigger consideration when a car is sold globally. A couple of the guys said they weren’t really needed and took theirs off. If they stick, it could hinder flow. But if a mouse does get in, it could smell really bad when you start up the engine. Hummm. (IMG:http://www.914world.com/bbs2/html/emoticons/barf.gif) |
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