fan shroud modification...

millerje78 · Posted: Thu Jan 26, 2006 10:45 am Post subject: fan shroud modification...

Since I don't have the money to buy a 181 or raby Type I cooling shroud, I wonder, why can't I cut off the fresh air outlets in my 66 shroud and weld them shut? I read that this isn't a good plan, but I didn't catch why. Could somebody shed some light on this please?

-jesse
_________________
always seeking a better way
my 73 standard project

do your research, consult with experts, and buy quality parts. you won't be sorry

Jake Raby · Posted: Thu Jan 26, 2006 11:00 am Post subject:

You can...
BUT you will more than likely disrupt the factory airflow that the factory worked so hard to create...

All it takes is a very small change to compromise the efficiency of the cooling system.

Also beware that if you are still running heater boxes that AIR MUST FLOW THROUGH THEM AT ALL TIMES to cool them, else you'r heads will fry. If heaterboxes are in place the fresh air tubes must also be in place.
_________________
Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell"

Glenn · Posted: Thu Jan 26, 2006 11:40 am Post subject:

A modified Dog House is not as good as a real 73 Type 181.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

עַם יִשְׂרָאֵל חַי

millerje78 · Posted: Thu Jan 26, 2006 4:53 pm Post subject:

hello again,
I realize that a sliced up and welded shroud is not as good as the 181 shroud; and its clearly not as good as the Raby shroud, but why? I was hearing what Raby was saying about even the most minute detailing of the shroud affecting its cooling capability, but why is this? I guess what I'm getting at here is, does anyone have pics or diagrams of a dissected fan shroud? Is there some sort of veining or patterns inside there that I don't know about? I am looking for a technical answer here.

by the way, you guys are awesome. I didn't realize who I was talking to on this website until I researched a little outside of it... Embarassed

-jesse
_________________
always seeking a better way
my 73 standard project

do your research, consult with experts, and buy quality parts. you won't be sorry

veedubcrazy · Posted: Thu Jan 26, 2006 5:15 pm Post subject:

i am going to throw this out there on account of a lot of people do this... what about the freeze plugs that fit into the heater outlet of doghouse shrouds? that effectively stops the air basically the same as just neatly welding the holes closed. the vanes inside directing the air into the heater scoop just get blocked off. i think this would be a good alternative to someone that doesnt have the money for a type 181 shroud but also doesnt want the heat outlets showing. i think it can work.
_________________
1967 Deluxe Sedan
1971 Squareback - "The Silver Surfer"

RIS · Posted: Thu Jan 26, 2006 5:30 pm Post subject:

I converted a German fresh-air shroud into a Type 181 look alike for my '57 Oval. I cut the heater outlets off flush, then hammered the largerst pieces flat and used them to fill in the resulting holes. It looks good, as for cooling abilities I can't say if it's better than original, but I feel better about it than a crappy EMPI 36hp shroud. Plus I can still run the thermostat and control flaps...
_________________
Richard Sedoris - VW Performance & Machine - Youngstown, OH
http://rismachine.tumblr.com/
YouTube: https://m.youtube.com/channel/UCfTBCG4I61iVm_ROc8OAuOQ
Instagram: @rismachine

millerje78 · Posted: Thu Jan 26, 2006 7:17 pm Post subject:

At the moment, I am running j-tubes with a merged header, so I don't have the heating capability, but I still like the "stock" appearance of the accordian tubes since I have the provisions for them in the shroud. What I did is I cut out little circles of metal that fit tightly inside the tubes, restricting air flow so that cooling air is not lost. the heater tubes just sort of hang out the bottom of the rear tin an inch or so. its all a big sham!!

Image may have been reduced in size. Click image to view fullscreen.

veedubcrazy, plugging them directly at the outlet would be ok, but what I'm really after is space. I am putting some dual weber icts on soon, and I am thinking those outlets on the shroud will be in the way for sure.

RIS, I think I'll just go for it and cut them off flush, using the existing metal to plug the holes as did you. i don't foresee a major problem with this. I mean, that cooling air would have been lost to the heater anyway, right? how can it hurt things to force more air down over the cylinders.

thanks for the info men. i appreciate it.

-jesse
_________________
always seeking a better way
my 73 standard project

do your research, consult with experts, and buy quality parts. you won't be sorry

bartman · Posted: Thu Jan 26, 2006 9:11 pm Post subject:

i dremeled mine off and covered the holes with pieces of sheet metal. this is the best pic i could find handy. that's one of the covers just to the left of the oil line http://publish.hometown.aol.com/bernardbartman/myhomepage/oil%20filter%20mount.jpg?

Jake Raby · Posted: Fri Jan 27, 2006 7:41 am Post subject:

I incorporated the modification of a stock 1971 doghouse shroud into my testing. This shroud was tested before and after the removal of the heater snorkels.

In this test the temperatures of the #3 cylinder increased 35 degrees after the snorkels were removed and the temperature of #1 DECREASED 15 degrees, this is a typical trait of cooling system modifications that disrupt the airflow.
The designers of the stock shroud were not dumb and they had very open wallets to get the job done which is clearly evident with their results.

I have yet to make a single modification to a stock shroud that increased it's ability to do it's job better than it did before the mods were made and thats just the facts! I wish I could say otherwise, but all my efforts (and there has been plenty of them) were failures!
_________________
Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell"

Glenn · Posted: Fri Jan 27, 2006 7:46 am Post subject:

So... lets recap.

1) DTM... the best. Alot better than stock
2) 73 Type 181. Slightly better than stock.
3) OEM Dog House. Still the standard
4) Modified OEM. Not as good as stock
5) Aftermarket including Porsche style, GOL, center mount, 36hp style... worse than stock and you take your chances.

Is this correct?
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

עַם יִשְׂרָאֵל חַי

Jake Raby · Posted: Fri Jan 27, 2006 8:12 am Post subject:

The line up is as folows
DTM
Stock non modified (includes 181 in my testing)
36HP aftermarket
911 style shrouds
center mounted systems that utilize the stock radial fan (these are HORRIBLE)
VW Gol

Nothing performed as bad as the Gol shroud!

I saw no differences in cooling with the 181 shroud that would prove it's worth the money.

My DTM only beat the stock shroud by about 10% in average engine temperature, but it did significantly decrease temperature delta between all 4 cylinders. The biggest benefit of the DTM was the cooler oil temperatures due to the TIV cooler and the 17% of added airflow we direct through it over stock.
_________________
Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell"

Glenn · Posted: Fri Jan 27, 2006 8:44 am Post subject:

Thanks Jake... I hope to use this topic in the future when this question comes around again.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

עַם יִשְׂרָאֵל חַי

millerje78 · Posted: Fri Jan 27, 2006 10:53 am Post subject:

thanks for the run down on cooling. That was exactly what I was looking for. Maybe I'll try to install the duals and see how they fit before I hack up my shroud. I want to convert to doghouse at some point. Any good kits out there?

-j
_________________
always seeking a better way
my 73 standard project

do your research, consult with experts, and buy quality parts. you won't be sorry

58Dub · Posted: Fri Jan 27, 2006 3:29 pm Post subject:

Thanks for the info Jake..but here's another question. The stock shroud was designed to push air out the heater outlets and through stock heat exchangers. This must cause some restriction on the air going through. So....using a stock unmodified doghouse shroud, and not having heater boxes...like many of us, is it better to plug the heater outlets or just leave them open? Confused

Thanks again

Glenn · Posted: Fri Jan 27, 2006 3:33 pm Post subject:

Jake Raby · Posted: Fri Jan 27, 2006 3:45 pm Post subject:

Yes, the air was to be metered by the heater boxes and the shroud was designed with this amount of bleed and back pressure in mind. I found that a freeze plug with a 1.5" hole in the center provided effectively about the same results as with heaterboxes installed, pressure wise within the shroud....

Remember that even when the heat is off, the air escapes from the heaterboxes through the tiny bleeders on top of them, there is always air escaping from those "snorkels" on the stock shroud, with the original design.

The same rule has applied to the TIV engine with the heater boxes removed- blocking the outlets in the stock shroud certainly has negative results- mine have been open on the Bus for 5 years. Blocking them off quickly elevates temperature differences and really heats up the #1 cylinder...
_________________
Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell"

Glenn · Posted: Fri Jan 27, 2006 3:53 pm Post subject:

So then can it be said that a 73 Type 181 shroud would be better to use than a late dog house with the fresh air outlets plugged?
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

עַם יִשְׂרָאֵל חַי

millerje78 · Posted: Fri Jan 27, 2006 3:58 pm Post subject:

Raby,
I hear what you are saying about the original design of the Type I shroud being made specifically for use with heater boxes, but you mention that afixing a freeze plug with a 1.5 inch hole in it can mimmick the affect of the back pressure that would have been there had the heater boxes still been installed.

what would be the difference between cutting off the snorkels; welding in patches with 1.5 inch holes in them, and leaving the snorkels on; capping them off with drilled out plugs? Do the air-flow dynamics depend on that little off-shoot (snorkel), or is it the hole that is necessary to maintain even cooling?

-jesse
_________________
always seeking a better way
my 73 standard project

do your research, consult with experts, and buy quality parts. you won't be sorry

veedubcrazy · Posted: Fri Jan 27, 2006 4:01 pm Post subject:

you know, unless someone actually cut open a t-181 shroud and a reg doughouse shroud (with outlet removed and welded over w/ sheet metal) and compared the two, we wont really know. i would bet they are the same. only diff is one has an outlet and the other does not. both have the same basic shape and attach to the upper tin the same way. even have the same inward slope to them. has anyone asked the german engineers? Wink

_________________
1967 Deluxe Sedan
1971 Squareback - "The Silver Surfer"

Glenn · Posted: Fri Jan 27, 2006 4:04 pm Post subject:

I'm not willing to cut either of the 2 I have. But i've heard they are slightly different inside.
_________________
Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

עַם יִשְׂרָאֵל חַי


Hello! Log in or Register \| Help \| Donate \| Buy Shirts	See all banner ads \| Advertise on TheSamba.com

Forum Index -> Performance/Engines/Transmissions		Share:
		Print View

	Forum Index -> Performance/Engines/Transmissions	All times are Mountain Standard Time/Pacific Daylight Savings Time Page: 1, 2 Next
Page 1 of 2