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Airflow, Scoops, Vents and High Temps....
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PostPosted: Wed Aug 02, 2017 1:26 am    Post subject: Airflow, Scoops, Vents and High Temps.... Reply with quote

To prevent Thread-jacking, I'm moving this here:

So, yesterday, I sent Waldi a PM giving him some parameters, and asking for his opinion to validate a theory that I had come up with.
As I was hanging out with some of VFW buddies last night, we came upon a problem with my airflow setup.

I have the late-model vents installed on my rear windows:
Image may have been reduced in size. Click image to view fullscreen.

I have cool looking scoops mounted too:
Image may have been reduced in size. Click image to view fullscreen.


After my high temp situation (PM), I took apart some 550 cord, and tied some of the little strings around the vents to see airflow (in the mirror).

It looks to me that the window vents are pushing air OVER the scoops, therefore negating them. So the scoops might actually be hurting my cooling ability (it would be easier to remove the scoops than the vents!).

Does this sound like a reasonable theory?
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Last edited by Team WorldTour on Wed Aug 02, 2017 3:24 pm; edited 1 time in total
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Waldi
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PostPosted: Wed Aug 02, 2017 2:16 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

You didnt awnsered my question if you have a external oil cooler.
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PostPosted: Wed Aug 02, 2017 2:20 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

My understanding is that the engine bay is 'pressurised' by the airflow under the van and that these vents are therefore actually exhausts rather than intakes. Presumably the airflow along the side of the van creates extra suction to pull hot air from the engine bay out of these vents, and this would seem to be confirmed by your experience.
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PostPosted: Wed Aug 02, 2017 2:26 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

No, not any more. I had to remove it after I broke a weld on the cooler replacing the hoses.

I still have it in a box in my garage. IF I can find a replacement cooler, and if I can find a replacement temp probe, I would definately reinstall it.
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PostPosted: Wed Aug 02, 2017 2:32 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

clift_d wrote:
My understanding is that the engine bay is 'pressurised' by the airflow under the van and that these vents are therefore actually exhausts rather than intakes. Presumably the airflow along the side of the van creates extra suction to pull hot air from the engine bay out of these vents, and this would seem to be confirmed by your experience.


This is for sure wrong.
If you dont belive what my cooking instrument shows, (check the old scoop post) measure by yourself.
For me a practical test goes over theorie.
I know some believers think different Wink
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PostPosted: Wed Aug 02, 2017 2:34 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

clift_d wrote:
My understanding is that the engine bay is 'pressurised' by the airflow under the van and that these vents are therefore actually exhausts rather than intakes. Presumably the airflow along the side of the van creates extra suction to pull hot air from the engine bay out of these vents, and this would seem to be confirmed by your experience.


I'm not sure if this is correct. At least I'm sure it isn't correct for my setup.
I'm running a Diesel Syncro. Not only do I have a VERY large skid plate (PLATE being the optimum word!), with only three louvers under the turbo (by their orientation, it's logical to see it is to remove air via low pressure).
Also, the Diesel has a 'diaper' sort of thing. Stock for my van is this. So logic dictates the air moves into the D pillar, and is forced past the exhaust manifold and turbo, and out the bottom.
I could also be wrong. My opinions tend to change upon observable facts.
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PostPosted: Wed Aug 02, 2017 2:40 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

Team WorldTour wrote:
No, not any more. I had to remove it after I broke a weld on the cooler replacing the hoses.

I still have it in a box in my garage. IF I can find a replacement cooler, and if I can find a replacement temp probe, I would definately reinstall it.


Thats your problem with high temps.
The AAZ oil on summer temps highway will heat up over 120C.

http://www.ebay.de/itm/Olkuhler-Motorol-Original-V...SwRXRZPSfK

Check my gallery how to mount it.
You have a Mocal adapter with thermostat ?
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PostPosted: Wed Aug 02, 2017 2:46 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

I still have the original parts Mr. Tencent's oil cooler came with. I'm going to assume you mean the Sandwich Plate? Yes, I have it still.
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PostPosted: Wed Aug 02, 2017 3:32 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

Air scoops...... oh the pages and pages you can read about these interesting things.

A few things are 100% clear.

They were a "must have" when the body was first produced with an air cooled engine. These scoops were THE source of life giving cool air.

Then along came the diesel, the 1.9 and eventually the 2.1 in the NA market.
The scoops stayed but were they needed?

Clearly they vent hot air once the engine is shut down.
But do they provide any useful air to the water cooled engines that lurk below?

When the 2.1 was introduced in 1986 they ran a snorkel up the right vent to capture air to feed the air filter..... why? Is there no air down there? Is it too dirty or too hot? Does a ram induction help the 2.1 run better?

Many have taken readings on air flow but none of these are dead accurate or conclusive.

It is fun to talk about, interesting to read about but what real purpose do they serve for the water pumper crowd?

Some have put oil coolers in them, some have put radiators in them, some want to seal them up and harvest the wasted storage space they occupy in the D pillars.
Some hate them for they collect water and rust.

Dave
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PostPosted: Wed Aug 02, 2017 4:16 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

djkeev wrote:
Air scoops...... oh the pages and pages you can read about these interesting things.

A few things are 100% clear.

They were a "must have" when the body was first produced with an air cooled engine. These scoops were THE source of life giving cool air.

Then along came the diesel, the 1.9 and eventually the 2.1 in the NA market.
The scoops stayed but were they needed?

Clearly they vent hot air once the engine is shut down.
But do they provide any useful air to the water cooled engines that lurk below?

When the 2.1 was introduced in 1986 they ran a snorkel up the right vent to capture air to feed the air filter..... why? Is there no air down there? Is it too dirty or too hot? Does a ram induction help the 2.1 run better?

Many have taken readings on air flow but none of these are dead accurate or conclusive.

It is fun to talk about, interesting to read about but what real purpose do they serve for the water pumper crowd?

Some have put oil coolers in them, some have put radiators in them, some want to seal them up and harvest the wasted storage space they occupy in the D pillars.
Some hate them for they collect water and rust.

Dave


I agree with you that the scoops will not help significant to cool down the engine oil or water temps, as a oilcooler does or a new watercooler instead of the 20 year old one.
But there are still some reasons to take scoops.
1. air-air intercooler
2. hot sommer temps, as the engine (and bellhousing) does not run in 70C
3. cooler engine room and side vents do not heat up the inner of the van as much as hot engine room.

Ppl spend so much money on useless gimmiks for the van.
What about we are talking ? 50-100 buks ?
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PostPosted: Wed Aug 02, 2017 5:24 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

Waldi wrote:
clift_d wrote:
My understanding is that the engine bay is 'pressurised' by the airflow under the van and that these vents are therefore actually exhausts rather than intakes. Presumably the airflow along the side of the van creates extra suction to pull hot air from the engine bay out of these vents, and this would seem to be confirmed by your experience.


This is for sure wrong.
If you dont belive what my cooking instrument shows, (check the old scoop post) measure by yourself.
For me a practical test goes over theorie.
I know some believers think different Wink


I'm happy to be corrected, although I am aware of observations by others that suggest the engine bay is under positive pressure. Whether this means that the airflow through the d-pillars is upwards or downwards obviously seems to be the subject of much discussion.
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PostPosted: Wed Aug 02, 2017 6:09 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

It wouldn't be hard with a digital probe thermometer to tape the probe in the intake vent and go for a ride. If the probe reads significantly higher than ambient temperature (not in the sun) then warm engine air is venting.

Ambient temperatures? Air is being sucked or rammed in. Easy Peasy........

I would think though, that if warm engine air is venting while driving, that oily residue one finds on the oil check door and other locations would coat those vents. (Except for Kam who hasn't any dirt on her engine 😂 )

On my 86 with the snorkel, the bottom of the right vent channel is completely blocked off with a plastic cover.

Honestly, I tend to think that water pumper units kept the vent as a design feature for aesthetics only. Not unlike the fake fender vents on Oldsmobiles and Buicks.


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PostPosted: Wed Aug 02, 2017 6:38 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

djkeev wrote:
It wouldn't be hard with a digital probe thermometer to tape the probe in the intake vent and go for a ride. If the probe reads significantly higher than ambient temperature (not in the sun) then warm engine air is venting.

Ambient temperatures? Air is being sucked or rammed in. Easy Peasy........

I would think though, that if warm engine air is venting while driving, that oily residue one finds on the oil check door and other locations would coat those vents. (Except for Kam who hasn't any dirt on her engine 😂 )

On my 86 with the snorkel, the bottom of the right vent channel is completely blocked off with a plastic cover.

Honestly, I tend to think that water pumper units kept the vent as a design feature for aesthetics only.


Dave


Come on please.
Do you ignore what i have measured ?
Exactly this:
"with a digital probe thermometer to tape the probe in the intake vent"

https://www.thesamba.com/vw/forum/viewtopic.php?t=...p;start=40

From 40kmh there are ambient temps with scoops.
Temp going down from 70C while standing still, down as you start to drive to 30C ambient.

Why do front engines run cooler than back engines ?
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PostPosted: Wed Aug 02, 2017 6:52 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

I propose that someone remove their engine cover and duct tape a piece of plastic over the hole. Go for a drive. If the plastic balloons up the bay is pressurised, if it sucks down then its got a vacuum on it. Take it one step further and cover the vents and go see what happens . Might be interesting..?
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PostPosted: Wed Aug 02, 2017 7:43 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

alaskadan wrote:
...
Might be interesting..?


Not realy.
As we want to know if the temp gets lower in engine room with scoops or without.
Overpressure in the engine room from under the car with the hot air from watercooler does not help.
And i would be surpriced if the ingeneers put the schnorchel up into the pillar, spending money, if it would get hot air there while driving.

With scoops there is more pressure from up, than from down.
That is a fact.


I will measure the temp in the pillar in my other syncro without scoops next days.
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PostPosted: Wed Aug 02, 2017 8:06 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

alaskadan wrote:
I propose that someone remove their engine cover and duct tape a piece of plastic over the hole. Go for a drive. If the plastic balloons up the bay is pressurised, if it sucks down then its got a vacuum on it. Take it one step further and cover the vents and go see what happens . Might be interesting..?


The plastic will balloon up. There is pressure in the engine compartment, even with the stock side scoops. However, there is also pressure in the upper portion of the stock scoop plenum. The pressure in the engine compartment and the pressure in the upper part of the scoop plenum is pretty close to the same which makes airflow through the plenum relatively stagnant. This is why adding the larger side scoops adds flow; It increases the pressure in the scoop plenum which overcomes the lower pressure in the engine compartment. This creates air flow. And further, adding openings to the rear license plate area increases the flow even more by decreasing the pressure in the engine compartment. Increasing the pressure in the scoop plenum by adding larger scoops and decreasing pressure in the engine compartment by adding openings in the license plate area increases the air flow dramatically. This has been proven, not just theory.
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PostPosted: Wed Aug 02, 2017 8:40 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

^^^^ It makes sense that opening up the license plate area would help to move air out of the engine compartment. The back of the bus at speed is a low pressure area for sure.
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PostPosted: Wed Aug 02, 2017 8:42 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

"adding openings"

I just dont close the service flap (Klappe) fully. That is nuff.
Dont push it to close fully just leave it nearly closed by the springs.
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PostPosted: Wed Aug 02, 2017 8:46 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

Waldi wrote:
djkeev wrote:
It wouldn't be hard with a digital probe thermometer to tape the probe in the intake vent and go for a ride. If the probe reads significantly higher than ambient temperature (not in the sun) then warm engine air is venting.

Ambient temperatures? Air is being sucked or rammed in. Easy Peasy........

I would think though, that if warm engine air is venting while driving, that oily residue one finds on the oil check door and other locations would coat those vents. (Except for Kam who hasn't any dirt on her engine 😂 )

On my 86 with the snorkel, the bottom of the right vent channel is completely blocked off with a plastic cover.

Honestly, I tend to think that water pumper units kept the vent as a design feature for aesthetics only.


Dave


Come on please.
Do you ignore what i have measured ?
Exactly this:
"with a digital probe thermometer to tape the probe in the intake vent"

https://www.thesamba.com/vw/forum/viewtopic.php?t=...p;start=40

From 40kmh there are ambient temps with scoops.
Temp going down from 70C while standing still, down as you start to drive to 30C ambient.

Why do front engines run cooler than back engines ?


Not ignoring, obviously didn't see it.........
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PostPosted: Wed Aug 02, 2017 9:29 am    Post subject: Re: Airflow, Scoops, Vents and High Temps.... Reply with quote

dobryan wrote:
^^^^ It makes sense that opening up the license plate area would help to move air out of the engine compartment. The back of the bus at speed is a low pressure area for sure.

I did just that on a long hot (106* F) trip years ago. Made cardboard deflectors for scoops to introduce cooler air and propped open the licence plate door to vent the hot.

It dropped the temp gauge needle ~1/8".
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