air flow

[dokarex]

Anybody have an idea of how much air flows through the vents on the side wheel arch back into where the stock snorkel location is on a 2wd Doka?
The reason for this question is I want to install an intercooler where the snorkel comes into the engine bay I know the engine is able to suck clean cool air but how much flow is there without assistance. I plan on installing the IC in this cavity then covering it with a SS plate to block it off from the engine bay then venting it out under tail light with some custom louvres or vent. Is there enough air flow if this is done or will it need a fan, I don't think leaving it open to the engine bay will result in enough cooling (wouldn't the air just swirl around and pick heat up from the engine) and a direct flow from the stock louves then out the back under the tail lights should resut in a better flow and cooler air, especially if I install a fan.
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1987 Doka 1.9TD from Germany gasser DU tranny, fuel turned up, 1.6 LDA pin, boost at 15 psi,egt and boost gauges,stock diesel tach,air filter behind passenger tail light, IC to come
2006 Jetta Wagen 1.9TDI
B6200 Kubota Diesel
16ft Freestyle catamaran
16 ft Sunray 85 Horse (sunk)

[Christopher Schimke]

This may not give you the exact answer that you are looking for, but it might give any idea of the direction to look.

I did some airflow testing my Vanagon just out of curiosity. Granted the Vanagon is not a Doka, but I think that the Vanagon has better airflow through this area, so the Doka will probably have less airflow through this area, even if only slightly.

I attached a magnehelic pressure differential gauge to my dashboard (0-2.0 scale) and ran the "high" pressure test tube to the front of the van and attached it right between the upper and lower grills. This is to assess the highest pressure available on the van and to simulate the incoming pressure available to a front mounted intercooler. Then the "low" pressure tube was attached to various areas in and around the rear vent opening, inside the plenum, inside the engine compartment and the rear of the van. The numbers listed are the pressure differences between the high pressure front of the van and the rest of the areas tested.

The one that surprised me the most was how the removal of the louvered panel from the vent opening changed the pressure.

Here is how it played out.

There is probably some huge flaw in my testing procedure, but it really wasn't meant to be super scientific, it was just for fun and I think that the numbers are interesting.
_________________
"Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)

*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected]

[PDXWesty]

Great data! If you know the cross section area of the pillar and the differential pressure as Loogy measured it, there are equations to calculate the airflow down the pillar. A differential pressure of 0.1" water column is actually quite a bit. I'm a bit cautious about the measurement at the front of the van though. There is an unknown velocity pressure componant in there along with the static pressure reading and the calculations could be quite a bit off. Whether the tube at the front was placed into the wind or perpindicular to the airflow will change the readings quite a bit.
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89 Westy 2.1 Auto

[ragnarhairybreeks]

Geez Loogy, you mean you actually did the experiment instead of just thinking about it for years ?




My gauge still sits in the workshop, now mocking me more. Sheesh.

edit: I was thinking about placing the reference tube inside the van as opposed to outside at the front. Don't know if that makes real sense or not
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[Christopher Schimke]

Yeah, like I said, there is probably a huge amount of improvement that could be done to solidify the data, but I am not an airflow expert, I just wanted to play around a bit out of curiosity.

The front hose was placed perpendicular simply because pointing it straight into the wind caused my gauge to peg under all conditions. While I know that this isn't ideal, but I did what I had to just to get SOME readings. And just for the record, the low pressure hose was always placed perpendicular to assummed airflow as well.

It probaly couldn't happen for a few weeks, but I would be happy to repeat the tests using whatever proceedure is deemed more useful.
_________________
"Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)

*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected]

[PDXWesty]

The best place to place the tubes to measure airflow down the pillar would be just inside the rear intake grille and at the bottom inside the engine compartment. The closer you can get to the inlet and outlet of what you want to measure, the more accurate the readings will be. Make sure the ends of the tubes are perpindicular to the airflow.
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89 Westy 2.1 Auto

[Christopher Schimke]

[Christopher Schimke]

[ragnarhairybreeks]

interesting stuff about interior pressure readings. I guess its confusing the original issue, but fun.

i'd thought about placing tube end on various spots on outside of van, (still hadn't decided on high pressure fixed point, probably on radiator). I wanted to measure just how low the low pressure area was at rear of van, and on various roof positions.

Now I am inspired to repeat your work. Couple of things:

1. wondering if some sort of baffle on ends of tubes would be good idea to reduce tube orientation importance
2. propping license plate hatch open to see what happens to pressure at base of intake vents.

short article here on same subject:
http://autospeed.com/cms/title_Undertrays-Spoilers-Bonnet-Vents-Part-1/A_2159/article.html


alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[PDXWesty]

Using a pitot tube is the most accurate way to measure airflow pressure. It seperates the componants of velocity and static pressure. But as long as you keep the end of the sampling tube perpindicular to the airflow, you should be ok.

http://www.engineeringtoolbox.com/pitot-tubes-d_612.html
_________________
89 Westy 2.1 Auto

[ragnarhairybreeks]

pitot tube yes, and not wanting this this discussion to digress too much, I was thinking of something less sensitive to orientation so that one could tape or insert end of tube to measuring spot easily.

crazy idea like a open cell foam baffle, that may/will slow down meter response.


know what I mean?

alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[dokarex]

Holy cow Loogy
When you talk about the Inside Bottom of Sealed Right Pillar, Is this the cavity infront of the tail lights? That's where I'm going to mount it but on the drivers side (left?) I'm thinking a Doka would actually have more air flow because of the louvre above the rear wheel, expecially if I add the same type of louvre under the tail light and seal it off from the engine compartment.
_________________
1987 Doka 1.9TD from Germany gasser DU tranny, fuel turned up, 1.6 LDA pin, boost at 15 psi,egt and boost gauges,stock diesel tach,air filter behind passenger tail light, IC to come
2006 Jetta Wagen 1.9TDI
B6200 Kubota Diesel
16ft Freestyle catamaran
16 ft Sunray 85 Horse (sunk)

[Christopher Schimke]

[Christopher Schimke]

[240Gordy]

You need a NACA type duct on the side of the doka instead of the louvers, something like what is on the swiss race taxi to feed the 996(?) intercoolers, only in the area below the bed of course.

google it and you will find you can buy them ready made.

puresxy NACA ducts . . .

sexy=functional
_________________
Tencentlife said,
"So, now that you know what you're doing, go to town."
2010 GOLF TRENDLINE 2.5
1985 GL now with more! a 2.1L
H&R SPORT(RED) Springs FRONT , SLAM SPECIALTIES RE6 AIRBAGS REAR

[dokarex]

Exterior scoop in this area would be hideous, I think I'll try it as is and if necessary add a fan to push or pull the air through the IC.
_________________
1987 Doka 1.9TD from Germany gasser DU tranny, fuel turned up, 1.6 LDA pin, boost at 15 psi,egt and boost gauges,stock diesel tach,air filter behind passenger tail light, IC to come
2006 Jetta Wagen 1.9TDI
B6200 Kubota Diesel
16ft Freestyle catamaran
16 ft Sunray 85 Horse (sunk)

[1621]

Isn't that essentially what Eric did on his STi converted Tristar? I seem to recall he used a Porsche side mirror housing or something along those lines. Can't find the thread here or on the vortex though.

_________________
'85 Westy

[JunkYarDog]

Ok, just because I find this stuff to be very cool... What effect do you think it would have if you were to install spacers to set the tail light housings out, opening a pathway from the rear on pressure in the intake channel?

If I read your graph right, the scoop tended to be counter productive. But the louvers were a little too.. It's funny as I am running with mine removed at the moment. I had to access the drain tubes for the sunroof, all the rain was backing up and dumping in when I would start to go (bad day!!!)

While I have them off I was considering experimenting with some alternative designs. I have a second set I was thinkning I could modify to increase flow/pressure in the channel. If I do anything in that line I wouldn't be able to test it as you have but can let you know if it seems feasible for testing..

Anthony
_________________
I have never owned a VW I didn't like, but there have been a few Fords and Chevy's.
85' GL Sunroof
68' Beetle sedan
72' Chevy C10 (LWB Step)
(67' Volvo 122S pending)

[Christopher Schimke]

Actually, the scoop decreased the pressure differential in the plenum by quite a bit with the louvers both installed and removed, although the pressure differential was slightly lower with the louvers installed.

On the chart above, the lower the number, the the better (better being a relative term). This is because the gauge that I used has two ports on it, one for the higher pressure area and one for the lower pressure area. The number that reads on the gauge is difference between the two areas being tested. The closer to zero the gauge reads, the more equal the pressures are in those areas.

The experiment was not so much to prove that adding a scoop to a sealed rear vent plenum created more pressure in that area (even though it did confirm that) because others have already proved that in the past. What I primarily wanted to know was the difference between a sealed and unsealed plenum chamber, the difference between the pressure inside the engine compartment and the outside rear of the van (both with sealed and unsealed plenums) and to see what affect the louvers had on the pressure in the plenum.
_________________
"Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)

*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected]

[240Gordy]

someone pointed out to me that the only advantage to the NACA duct was that it is a low drag solution, and my reply is why add more drag to an already less than ideal shape? (however beautiful it might be)

Loogy, is the number the difference or is it ratio of that number or a percentage, like if the value is .650 it seems it means it is 65% of the high pressure location? Or am I misunderstanding it?
_________________
Tencentlife said,
"So, now that you know what you're doing, go to town."
2010 GOLF TRENDLINE 2.5
1985 GL now with more! a 2.1L
H&R SPORT(RED) Springs FRONT , SLAM SPECIALTIES RE6 AIRBAGS REAR