fan shroud air flow with and without ventuir ring (data heavy)

[volkaholic1]

i have been doing a bunch of testing on my mom's stock bug on thermostats, i did this, but i think it is important enough that it should get its own disucession,

you can read about my thermosptat testing here if you want to
https://www.thesamba.com/vw/forum/viewtopic.php?t=705328&highlight=

i mounted an anemometer to a piece of wood, it will get barely fit between teh shoud and the top of the engine, puts the meter about 1.5" form the firewall and 1" from the fan inlet, i am trying real hard to NOT get the meter (o rmy hand) into the fan!

with the stock fan, meter set on "max" airflow, i recorded the air flow at 1000, 2000, 3000, and 4000 rpm

then i installed a venturi ring, now i make these, and i always tell folks to weld, braze or pop rivet them on, not to use screws as they can come loose, but i had planned ahead, i saftey wired the bolt to the shroud, drill a hole in the bolt, welded in a bent over washer, so now impossible to come loose, hard to get good pics, but you can imagine it

again, test at 1000,2000,3000 and 4000 rpm


take the ft/min speed results, multply bey the cross secitonal area of the fan in f^2, you get ft^3/min.

this chart has 2 axis, the blue line is ft^3/min increase in airflow, scale on the left, orange line is % increase in airflow, scale on the right.

so, you get 7.3% more airflow with the venturi ring install across the entire rpm range,,, pretty cool i think,

your thoughts?

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Volkaholic

[gimmesomeshelter]

Cool!

For the 356/36hp people, using the venturi ring provides 28 blade fan air flow with a 16 blade fan.

Cheers,

Paul
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[oprn]

Do they make one for the type 4 Bus engine? There is where the real need is!

[Wreck]

Just curious , what is the ID difference from the velocity ring to the standard shroud ?
It wouldn’t be about 7% smaller by any chance , same volume of air but at a higher airspeed .

[volkaholic1]

the fan inlet is 6" dia, the venturi ring is 5" dia at the min, but remember, air still flows in from around the venturi ring, not just up the middle.
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Volkaholic

[Wreck]

It would be nice to get back to back CHT results with the engine in a dyno room , I remember reading some where that the Venturi ring was to help quieten the fan , did you notice any difference in noise ?
Great experiments and info by the way .

[volkaholic1]

it just change engine sound , i would not say louder or quieter, just different
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Volkaholic

[bugguy1967]

This is great. Thank you!
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[nextgen]

On Buses for sure, they need all the help they can get.
But on Cali Style T-4 Upright Conversions, using 36 hp dog house in a bug, 912e 356 etc , the T-4 is hardly working to push the light vehicles. I had to increase my Thermostat to 90c. On some cooler days I had a problem reaching oil running temp of 170,
Going to be putting in new rubber around my cooling tin and have been driving the car without the sealing rubber. Doing 75mph for 35 miles on a 90 f day my oil temp made 210f. Actually thinking of not putting the rubber back 210 f is fine at that speed and air temp.


Not having heater boxes does help. Once the heater boxes heat up, that is a lot of metal rising vs headers.
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[richparker]

Thanks for taking the time to do the experiment and posting the results. I’m currently having a 2275cc built for my ‘71 bus and it will have the ring installed. I’ve read a lot about the benefits, but I’ve never seen any hard numbers. Thanks!
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[Axitech]

Where did you get the sweet red anodized twist-pliers?
Oh yeah, and the Venturi rings, for sale anywhere?
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[volkaholic1]

i sell the venturi rings, on here, ebay and my website awesome powdercoat dot com
:
the pliers are called "aviation twist pliers" - i think i got them off amazon, not too expesive as i recall
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Volkaholic

[richparker]

[gt1953]

I have a stock venture ring fan schroud not in use and this may move me to either use it or sell it.
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72 type 1
72 Squareback
({59 Euro bug, 62, 63, 67, 68, 69, 73 type ones 68 & 69 type two, 68 Ghia all sold})

[Ebel]

The pliers are painted. The only way they could be anodized would be if they were made of aluminum. Aluminum won’t make real good pliers.

[oprn]

I am running on the high side for oil temp on my type 4 in my Manx clone. I have been told that the stock Bus cooling system is more than adequate and I do believe it to be true but... on and open engine Buggy the fan inlet is down low and in a partial vacuum. I don't have cylinder temp gauges working yet but really don't feel the heads are hot. No heat soak issues with the carbs and no browning of the heads under the tappet covers. No loss of power at speed or hot hard starting.

I have seen oil temps as high as 240* F at 65 - 70mph. That would be expected on a Bus but a 1400 lb Buggy? One possible contributing factor may be that I grooved the big end of the rods for more oil splash on the bottom of the pistons so the oil may be carrying away more heat than normal.

Maybe not but I'm just wondering if a ring would make a difference.

[67 Sunroof]

I just bought a Venturi ring. For $50 it’s a no brainer

[[email protected]]

I had a customer with a 70 Bay with the stock SP 1600 I wanted to keep as cool as possible. I put a wide fan, doghouse shroud with an Awesome Powdercoat venturi ring on the engine. It would run down the highway at 60mph all day with case temps around 205 measured with an IR gun. Putting around town, it would barely get to 180 with the thermostat hooked up. They’re going on every personal engine.

[nextgen]

oprn, well I guess VW seals the engine compartment for a reason......... But like you said were the intake is.. also check timing, compression. Lean mixture????



As mentioned I am not running the rubber surround seal and my oil temp went up from 180 to 210 at the same speed and air temp. As you know little things can make a change.

Funny I went from 180 to 210 and you went from the safe 210 to 140.

we both went up 30 degrees.
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The TYPE IV UPRIGHT CONVERSION MANUAL
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[Ulu]

I bumped this both as a thank you to volkaholic1, a blessing to the great Bernoulli, and to say that I am going to embark on my own series of venturi airflow experiments with a plastic kit kar.

I intend to make fiberglass ductwork that both acts to reinforce the bodywork, and provide the most cool air possible (considering that I live on the edge of the great San Joaquin desert.) It will have the venturi device.

This is no commuter car and I don't care about economy. I'll probably drive the pizz out of it and rebuild the engine to larger dimensions in the first two years of random blitzin.


I have the time and money to do strange things to cars, and I live on the edge of so much twistiness. Much fun to be had if I can keep the rings from welding to the cylinders.