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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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 Posted: Sat Jan 01, 2011 9:39 pm Post subject: |
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| Cedge wrote: |
Stripped...
Took me a few minutes to dig up where I read it, but here it is...
http://bergmannvw.net/high-flow-fan-kits.html
He's at least giving lip service to "fixing" the known problems. Gotta admit, the individual parts don't look badly made.
Steve |
The fins behind the blade in the support ring redirect the air by helping to remove the swirl which is common technology. The high blade count of the fan helps prevent stalling the air flow and to build pressure. One thing I spot right away is the that you have 4 diverters and 12 fan paddles.....a real no no in fan design (and I know this subject). Divisible numbers like this create "pass" noise as there is a paddle lined up with each diverter all the time so there is a frequency pass noise that is RPM related. You want 5 or 7 diverters (5 would be better) so that no more than 1 paddle is ever lined up with a diverter at the same time. The other drawback to the even number is air pulsing since there is pressure build and release that varies with pass frequency........Bernie, Bernie, Bernie... If he insists on four diverters then he should at least use an asymmetric mounting configuration.
You still have the same issue of blowing back right into the rear vertical surface of the shroud over about 3/4 of the blade diameter (based on what I see in the pic). Blade design can help with this but won't completely overcome it. And if Bernie would offer SOME kind of under cylinder hardware at least he'd look like he was trying to do the right thing.
He obviously did not hire an expert for this "new development" and if he did then the guy was no expert and he should get his money back.
RC
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Cedge
Samba Member
Joined: October 19, 2010
Posts: 74
Location: Greenville SC
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| Posted: Sun Jan 02, 2011 7:33 am Post subject: |
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Rockcrusher
Seems OEM Porsche used the 4 vane 12 blade combo too...(grin)
Steve |
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Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 79782
Location: Sneaking up behind you
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| Posted: Sun Jan 02, 2011 8:05 am Post subject: |
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| Cedge wrote: |
Seems OEM Porsche used the 4 vane 12 blade combo too...(grin)
Steve |
I count 11.
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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
Last edited by Glenn on Sun Jan 02, 2011 8:12 am; edited 1 time in total |
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Glenn
Mr. 010
Joined: December 25, 2001
Posts: 79782
Location: Sneaking up behind you
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| Posted: Sun Jan 02, 2011 8:10 am Post subject: |
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Its funny that Bergmann shows a 12 blade fan... i assume it's not genuine Porsche.
So show me a 911 with a 12 blade fan or a 901 part number on that fan.
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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 |
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Sun Jan 02, 2011 9:09 am Post subject: |
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I feel better to know that at least.....I......can count 
That's a lot of fan pics Glenn
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Cedge
Samba Member
Joined: October 19, 2010
Posts: 74
Location: Greenville SC
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| Posted: Sun Jan 02, 2011 9:21 am Post subject: |
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I stand corrected.... 11 blades it is. Hell....Rock, cut me some slack... I didn't have time to take my shoes of....eh?
Steve |
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Sun Jan 02, 2011 10:18 am Post subject: |
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Porsche made 5, 11, and 12-blade fans for different 911 models throughout the many years they were in production. The diffuser rings also varied in the number of vanes, too.
But it is good to see that you guys can count.
_________________
| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Sun Jan 02, 2011 10:22 am Post subject: |
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| Glenn wrote: |
Its funny that Bergmann shows a 12 blade fan... i assume it's not genuine Porsche.
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No, it's not. It might be worth your while to at least read the article.
| Glenn wrote: |
| So show me a 911 with a 12 blade fan or a 901 part number on that fan. |
964's and 993's had a 12-blade fan. That's only a decade worth of production, so I understand if finding a picture of one is rare.
The catch to all of this is that the Porsche 12-blade fans flowed considerably less Liters/sec than the earlier 11-blade fans. So, I'm not surprised that Bernie increased the pulley ratio on these newer kits.
[Anecdotally (among the Porsche community), the 5-blade and 11-blade fans flow similarly at the same pulley ratio, and the 5-blade fan is supposedly more efficient (Jake and others have observed conflicting results); the 5-blade fan is considerably noisier at high RPM than the 11-blade fan when driven at the same pulley ratio.]
_________________
| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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Glenn
Mr. 010
Joined: December 25, 2001
Posts: 79782
Location: Sneaking up behind you
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| Posted: Sun Jan 02, 2011 10:49 am Post subject: |
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And i stand corrected.
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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
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Sun Jan 02, 2011 11:00 am Post subject: |
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What I'm curious about is why a stock cooling fan uses only about 10 hp and the belt starts slipping at higher RPMs, yet how can a Porsche fan have 2-3 times this parasitic load? What happened to the slipping belt? Is the Porsche top pulley just that much better?
FWIW, loosening the tension on the belt on a Porsche(style) fan will allow for slippage. 
_________________
| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Sun Jan 02, 2011 11:31 am Post subject: |
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| Stripped66 wrote: |
What I'm curious about is why a stock cooling fan uses only about 10 hp and the belt starts slipping at higher RPMs, yet how can a Porsche fan have 2-3 times this parasitic load? What happened to the slipping belt? Is the Porsche top pulley just that much better?
FWIW, loosening the tension on the belt on a Porsche(style) fan will allow for slippage. |
It is the difference in design of the 2 styles of fan. An axial fan blade will stall the air flow but continue to turn (cavitation) where the mixed flow Type 1 fan is more like a torque converter and the fan itself will stall (won't want to accelerate it's RPM).
The 5 blade porsche blade is noisier for the same reason some propellers are noisier....blade gap. More blades, less gap, less noise....and the frequency goes higher so is less noticeable.
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Sun Jan 02, 2011 11:33 am Post subject: |
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| Cedge wrote: |
I stand corrected.... 11 blades it is. Hell....Rock, cut me some slack... I didn't have time to take my shoes of....eh?
Steve |
It's all good. I can only count to 9-7/8 on my fingers due to an unfortunate accident and only 19-7/8 when I'm all in. 
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[email protected] Please use email for all general inquiries.
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Sun Jan 02, 2011 11:53 am Post subject: |
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| RockCrusher wrote: |
| It is the difference in design of the 2 styles of fan. An axial fan blade will stall the air flow but continue to turn (cavitation) where the mixed flow Type 1 fan is more like a torque converter and the fan itself will stall (won't want to accelerate it's RPM). |
Again, belt slippage has been noted at high RPMs with the Type 1 fan. If a load at high RPMs causes the belt to slip, and that parasitic loss of the Type 1 fan has typically been reported around 10 hp, then shouldn't that then be the limit of the transfer of power through the belt? And if that is the limit of power transfer, how then can the same belt transfer 2-3 times that power into a different fan without slipping?
Either the belt does not slip, opposite of what many exports report, or variables have not been controlled (e.g. belt tension) between comparative tests of fan parasitic losses on the dyno. Cavitation and stall aside, it's this inconsistency that has me wondering...
_________________
| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
Last edited by Stripped66 on Sun Jan 02, 2011 12:01 pm; edited 100 times in total |
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Glenn
Mr. 010
Joined: December 25, 2001
Posts: 79782
Location: Sneaking up behind you
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| Posted: Sun Jan 02, 2011 11:55 am Post subject: |
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| RockCrusher wrote: |
| It's all good. I can only count to 9-7/8 on my fingers due to an unfortunate accident and only 19-7/8 when I'm all in. |
I can count to 21 when i'm all in
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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
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Sun Jan 02, 2011 1:07 pm Post subject: |
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| Glenn wrote: |
| RockCrusher wrote: |
| It's all good. I can only count to 9-7/8 on my fingers due to an unfortunate accident and only 19-7/8 when I'm all in. |
I can count to 21 when i'm all in |
Ok then I'm 20-7/8........
_________________
[email protected] Please use email for all general inquiries.
I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly. |
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Cedge
Samba Member
Joined: October 19, 2010
Posts: 74
Location: Greenville SC
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| Posted: Sun Jan 02, 2011 1:18 pm Post subject: |
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So we've learned:
TC and I are rare and special VW people.
It's at least theoretically possible to make a 911 shroud work properly... but..
The Euro guys might have access to better options than the current US offerings.
The whole subject has put Jake into terminal burn out.
Rockcrusher is a nubbster
Glenn has family ties in Arkansas
Steve can't count worth a damn
VW people get passionate about any subject related to VW's
Samba has as many different opinions as it has members.
No one seems to have a good answer to the original question
Steve |
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Sun Jan 02, 2011 1:19 pm Post subject: |
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| Stripped66 wrote: |
Again, belt slippage has been noted at high RPMs with the Type 1 fan. If a load at high RPMs causes the belt to slip, and that parasitic loss of the Type 1 fan has typically been reported around 10 hp, then shouldn't that then be the limit of the transfer of power through the belt? And if that is the limit of power transfer, how then can the same belt transfer 2-3 times that power into a different fan without slipping?
Either the belt does not slip, opposite of what many exports report, or variables have not been controlled (e.g. belt tension) between comparative tests of fan parasitic losses on the dyno. Cavitation and stall aside, it's this inconsistency that has me wondering... |
You can equate that 10hp to the torque stall for that design fan....the resistance to pumping any higher pressure equalizes with belt tension and slippage occurs. I'm sure it varies somewhat with belt tension. Comparing it to the axial blade Porsche style is apples and oranges. Within reason an axial blade acts like a flat disk once you reach the air stall.....it just doesn't move any more air with additional RPM and so the load curve flattens far before any belt slippage can occur. I have no idea of the actual hp to drive a Porsche blade but if the Type 1 is 10hp then the Porsche is like 2-3hp since the diverters add load.....way lower anyway.
Considering the Porsche blade is designed to run consistent hi-RPM on the Autobahn or where ever, the type 1 fan wouldn't last long or cool properly at those sustained speeds. They really had to use that system for hi-perf compared to the low RPM beetle stuff.
RC
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[email protected] Please use email for all general inquiries.
I will be happy to speak to anyone who has a serious inquiry (meaning real potential business for RC enterprises) or a parts order. Due to machining noise causing missed calls all calls will be returned promptly. |
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Sun Jan 02, 2011 1:42 pm Post subject: |
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| RockCrusher wrote: |
I have no idea of the actual hp to drive a Porsche blade but if the Type 1 is 10hp then the Porsche is like 2-3hp since the diverters add load.....way lower anyway.
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I think you're spending too much time on stall and the differences in flow dynamics between the two styles of fans.
Forget that for a second.
Jake Raby has reported that it takes about 5-10 HP to drive the stock fan. He reported that various Porsche fans require 25-30 HP to drive (however, other people have reported less).
Given that information, here is my confusion:
The belt on the stock fan will reportedly start slipping around 6000 RPM. If the belt is slipping, that is because the force required to drive the fan any faster exceeds the frictional force capacity of the belt. How then can the Porsche fan draw 25-30 HP when the VW belt starts slipping at 1/2 to 1/3 of that power requirement?
There are only 4 possible answers; either:
- the belt does not slip
- the VW fan draws more HP than what has been reported, but the results were truncated to not include those values at high RPM
- the Porsche fan does not consume as much HP as been reported
- variation in belt tension contributed to differences in HP requirements between different fans
It's not about cavitation or stall or anything else; the fan belt and the dyno don't know the difference. The fan belt simply works until the load exceeds its frictional capacity or its tensile capacity, and the dyno just measures the difference from one condition to the next. If the VW fan belt slips, and it slips at the higher-range of what has been reported for the stock fan's HP requirements, then logically, the belt should not be able to support a load 2-3 times greater than that. It should be slipping. How does the fan belt slip on a stock fan at 10 HP, but not slip on a Porsche fan at 25 to 30 HP?
Again, one of those 4 possibilities is the answer. I'd like to learn which one. This is just a mental exercise borne out of the observation that my belt is slipping on my 911-style fan, and wondering how the heck am I loosing that much (reported) HP to drive the fan if the belt can't even transfer it.
_________________
| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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Glenn
Mr. 010
Joined: December 25, 2001
Posts: 79782
Location: Sneaking up behind you
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| Posted: Sun Jan 02, 2011 1:56 pm Post subject: |
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My fan belt slips at low rpm when I blip the gas. The engine can accelerate faster than the fan/alternator cam. It simply can't get the mass of the alternator to spin up as quick.
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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 |
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Sun Jan 02, 2011 2:02 pm Post subject: |
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Since I never even looked at an actual 911 engine in a car I don't know if there is an idler pulley. If so then there is your answer although I wouldn't imagine it takes 25hp to turn that fan at speed, but since I never dynoed one I sure am not the expert on that EXACT setup.
As to the type one.......look at how it acts when you rev it. The crank pulley is going clockwise and the fan/alt for the sake of argument WISH they were going the other way and so they naturally resist. What happens? The belt gets stretched on the outside and relaxes on the side where the distributor is and tries to walk up the side wall of the pulley. That's why the belt twists when the pulleys aren't aligned or is simply thrown off if they are. Once it relaxes and climbs there's comparatively no more drive left and it slips. With an idler you do 2 things. You eliminate the growth/relaxation AND you increase the surface area contact to the pulley.
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