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Vanagon Vent airflow direction?
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tobloyd
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PostPosted: Sat Jun 30, 2018 7:14 pm    Post subject: Vanagon Vent airflow direction? Reply with quote

It seems that the vents on the side of an air cooled vanagon are designed to scoop air in and channel it down to the engine compartment for cooling. But, does anybody KNOW that’ll be the case for certain?

The air is rushing past the side of the van at quite high velocity, and I know that increase in velocity corresponds to a decrease in pressure, so it’s certainly *possible* that the air is being scooped in somewhere from the undercarriage and being sucked *out* the vents (even though that seems counterintuitive).

Pease share if you happen to know the answer, and also please identify basis for your answer. Thanks!
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Paulbeard
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PostPosted: Sat Jun 30, 2018 7:23 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

There are threads on this…

Consensus seems to be that for water-cooled motors, the vents pull air down and into the engine at speed (they are forward-facing and angled to catch the air) and act as chimneys/passive exhaust when the motor is off or at a stop. Air-cooled motors use the fan to pull air down all the time. I missed that this was specifically about air-cooled motors: I thought it was understood that rear vents/scoops were the source of air for cooling.
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Jon_slider
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PostPosted: Sat Jun 30, 2018 8:05 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

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PostPosted: Sun Jul 01, 2018 4:31 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

Yes, there have been discussions on air flow down the rear vents but this discussion was focused on water cooled units.
Either stock WBX configurations or engine swaps, some putting "radiators" in the vent path.
People have posted videos using "tassels" while at speed as well as being stopped...... and a lot of great theory.

Things are different when talking about air flow on an AIR COOLED unit.

The air cooled has the top of the engine completely sealed from the lower part of the engine. The only air flow is via the engine fan blowing air over the engine.

The ONLY place the engine fan will draw cooling air from is these two side vents.

On an air cooled unit there is without a doubt air flow down the rear vents.

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PostPosted: Sun Jul 01, 2018 8:53 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

Don't some vans have a long factory snorkel that goes up there and sucks air in to the intake?

My aircooled has a short snorkel that sits at the bottom of the chimney, therefore air would need to be going into the vents.
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PostPosted: Sun Jul 01, 2018 12:04 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

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PostPosted: Sun Jul 01, 2018 8:30 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

So Dave I guess the air cooled is similar to the water cooled, as mine has a panel that blocks the airflow from the passengers side. The only air that passes is through the snorkel into the air cleaner. Of course the drivers side has no blockage so when your level sensor blows out of your tank the steam does come out the vent....but I was stuck in traffic and not moving.
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PostPosted: Sat Jul 07, 2018 12:20 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

I've measured up to 1/2" water column differential across my oil cooler matrix at speed at 6500'ASL. Even with the engine at full power drawing its air from upstream of the cooler, there's still enough airflow down the pillar and enough depression in the engine bay to induce a substantial differential. 1/2" w.c. doesn't sound like a whole lot, but in a large sectional area such as this that much differential will move a sizable volume of air. For comparison, the oil cooler's fan moves 330cfm and produces a palpably strong blast of air out the cooler, yet at standstill produced no visible column change in the manometer.
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PostPosted: Sat Jul 07, 2018 6:26 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

I think if VW wanted the airflow to go up through the air vents from the engine compartment then the design would have the opening facing the rear instead of designing scoops facing the oncoming airflow.
Just my opinion.
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PostPosted: Sat Jul 07, 2018 11:16 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

djkeev wrote:
On an air cooled unit there is without a doubt air flow down the rear vents.



Absolutely. With an air-cooled there is a seal around the tin to prevent air from being pulled from the bottom of the engine. If its missing, the engine will overheat. The license plate door is similarly sealed (or should be). The rear vents are the ONLY place to pull cold into the engine. When the engine isn't hot, you can feel a little bit of airflow into the vents at idle (or at least I can on my 82). At operating temps and at idle or when its turned off, heat does come out like a chimney (heat rises). I don't have any experience with a watercooled van, but I know they lack the engine tin, so maybe it works differently?
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Jon_slider
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PostPosted: Sat Jul 07, 2018 11:33 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

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PostPosted: Sun Jul 08, 2018 3:25 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

Jon_slider wrote:
84Cabby82Westy wrote:
With an air-cooled there is a seal around the tin to prevent air from being pulled from the bottom of the engine. If its missing, the engine will overheat. …


thanks for the education
that makes sense, I have no AC experience

I suggest an objective test:

put streamers on, and if they go down the chimney, it would confirm the fact

on this watercooled, the streamers do not go down the chimney

kamzcab86 wrote:

[youtube]https://youtu.be/rY8b5ftc[/youtube]


Again, there is no real need for streamers to test air flow on an Air Cooled engine.

As mentioned, with the engine properly sealed there isn't any other location the cooling fan can draw in air.
If the engine is running, air is being drawn into those vents.

This thread may help.......

https://www.thesamba.com/vw/forum/viewtopic.php?t=225562

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PostPosted: Sun Jul 08, 2018 5:46 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

I looked at the video Jon posted, I don't know how those streamers would do anything else on the highway, the velocity is just to much for them to be doing anything else. I don't know about you water cooled guys, but i do know that on my air cooled, those 2 vents are the only way cool air gets in and hot air escapes the engine bay.
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PostPosted: Sun Jul 08, 2018 6:23 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

Idling, my 68 bus would hold a piece of paper against the outside of the vent. My intercooler is at the base of the chimney with a cutout under it. I don't run an elec cooler fan. There is enough air movement through the cooler at speed to maintain 30F over ambient. I suppose the air flow could be from bottom to top. I don't have those window vents on my 82 shown with the streamers above.
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PostPosted: Sun Jul 08, 2018 6:32 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

tencentlife wrote:
I've measured up to 1/2" water column differential across my oil cooler matrix at speed at 6500'ASL. Even with the engine at full power drawing its air from upstream of the cooler, there's still enough airflow down the pillar and enough depression in the engine bay to induce a substantial differential. 1/2" w.c. doesn't sound like a whole lot, but in a large sectional area such as this that much differential will move a sizable volume of air. For comparison, the oil cooler's fan moves 330cfm and produces a palpably strong blast of air out the cooler, yet at standstill produced no visible column change in the manometer.


perfect! this is really the only measurement that applies. so with this real number, we can calculate the air velocity as Feet Per Minute airflow by taking the square root of the differential X 4005 = ~2800FPM. that's essentially a 30mph breeze in the vent cavity flowing thru the oil cooler. Chris- i assume the differential was measured at hwy speed, around 60mph? just as a point of reference, a straight 60mph headwind has a W.C. of 1.74"

i mounted my cooler in the drivers vent space as i had the room from my air cond delete. the faster i go, the better it cools as seen by reduced engine oil temps. the vent grill is always cool when i check immediately after stopping. if it was drawing engine bay air, it would be warm. empirical observations supporting measured data.

streamers taped near the vents are too subject to turbulence and kiting effect of the streamer itself to know much about the net air flow in the vent. a streamer IN the channel with a camera would be somewhat informative.
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PostPosted: Sun Jul 08, 2018 7:19 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

This is all very confusing and upsetting to me, I think I will drive my Van out to a pub and sit on the patio for a while. I hope that my engine stays cool. Maybe I could tape my kids budgie to an air vent and see if it is in the engine Bay when I get there, or maybe it will be blown clear during the drive.

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PostPosted: Sun Jul 08, 2018 10:23 am    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

Okay, I believe on the water cooled it's simply a hangover of the air cooled era. It was the 80s and louvered plastic was a "styling" thing. It was a cheap alternative and also staying with a design that has become signature to VW vans since 68'.

Had scoops been added during the air-cooled t25-t3, prehaps it would have been slower, creating a drag effect similar to a parachute. It may of even blew apart the seal separating the top from the bottom.

Scoops have shown to work by grabbing air that travels down the sides at speeds. Scoops are another subject!
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PostPosted: Sun Jul 08, 2018 12:11 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

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PostPosted: Sun Jul 08, 2018 12:17 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

The air vents on water cooled T3's are totally functional, serving to provide air both to the engine intake and helping to cool the engine bay. At speed air will travel down the stack and out under the vehicle, at rest the stack allows excess heat to vent upwards.
On the newer Vanagons with the plastic rear window vents, the airstream flowing along the side of the van will be somewhat diverted, lessening the inward flow to the stack. Hence, the add-on scoops to help.

Take a look at the newer "big window" T3's built in South Africa ('92-'03), these have a refined fresh air system which vents stale cabin air out of the rear of the van behind the air inlet at the stack.This eliminates the flow interruption of the window vent.
Clearly VW intended the vents to allow air into the engine bay even with the water-cooled versions.

I tried to find some clear pictures of the vent on these vans and only found a couple easy ones. You have to look closely to see the cabin air exit at the rear of the vent scoop.
https://www.gumtree.co.za/a-cars-bakkies/garankuwa...=Q317_Cars
https://www.gumtree.co.za/a-cars-bakkies/vereenigi...1263650309
https://campervanculture.com/2012/11/1992-south-af...ot-syncro/
https://www.youtube.com/watch?v=BQW88Z6w5bM

We've had this same discussion before. Rolling Eyes
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PostPosted: Sun Jul 08, 2018 12:21 pm    Post subject: Re: Vanagon Vent airflow direction? Reply with quote

DanHoug wrote:
perfect! this is really the only measurement that applies.


Jack Bombay did the same manometer test years ago, the results of which were posted in this forum, which I then reposted in the above-linked, lengthy thread on the same topic. But some people *cough* completely overlook or disregard that scientific evidence, instead choosing to focus on stupid little streamers taped onto the van while being driven on a road with outside environmental influences, rather than in an isolated wind tunnel. Nevermind the fact that VW put the engine air intake into the D-pillar, nevermind VW adding scoops to the S.A. van D-pillars, and nevermind the other empirical data posted in prior threads. Rolling Eyes

DanHoug wrote:
a streamer IN the channel with a camera would be somewhat informative.


My GoPro is charged up. I'll do that this week just so we can finally lay this beaten dead horse to rest. My dad just suggested a hinged flap mounted inside the pillar. Think
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