Not sure what to call what looks like a spun aluminum cover "bowl" "cone" to help the air be directed to the fan blades on a 4 cam motor ,
4 cams had double stacked fans but it might work on a regular pushrod motor fan too 
Just wondering .......
Photo from the "Rudi" auction website
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Everybody wants a 4-cam-look shroud and a lot of guys have tried. There was a discussion several years ago with a link to a Spyder with something similar to what @imperial is talking about. I think that's what Rick is talking about, and the link to the discussion/thread is HERE. There's a ton of good information regarding who's done it, how close they've gotten, etc.
The big names seem to be Bic Green and Ibrahim Kuzu. I don't think Bic's ever came to anything, and the Kuzu shrouds are $15k+ and don't seem to work.
Anand Rajani had one and posted the following:
@arajani posted:@chines1: Thanks for tagging me here!
First, I’ll start with a humble disclaimer: I am a 356 enthusiast (read: not an expert!). I care for critically ill babies for a living and work in the healthcare technology space. This stuff, while fascinating to me, is not something I understand at a deep level. I have no formal training in air-cooled engine building or engineering!
I had a 4 cam shroud on my spyder. When I chose to use transmission mounts to raise the motor and transmission in my CMI car (so that it would sit like the real cars do), the shroud did not fit. So I removed it.
Here’s what I do know from talking to John Willhoit. He does not recommend this shroud. A few reasons why:
Fan blades: The dual fans in the 4 can shroud move a ton of air. The blades should be welded (some of the early fans made by Bob Garretson, an original factory trained Carrera mechanic) did not do well when revved hard.
Generators: The generators also do come apart (an alternator will not fit in an early fan shroud). There is a place called BNR in Southern California that has methods of keeping this from happen at high revvs; we installed such a generator in my car. They are inherently less reliable than an alternator and are still subject to failing. Removing one from a shroud is no picnic (just ask Carey!!).
Cooling issues: 4 cam heads have substantial finning and can be well-cooled by this shroud. The air has to be directly very carefully over the heads of a type 1 or a 356 616 motor. Pat Downs build the engine tin for my build and spent HOURS making it perfect. Many do not also consider the crank pulley which needs to be sized down a bit (I believe the real 4 cams were 1:1). There’s a lot of engineering considerations and testing that should be done before one considers this. Anecdote: I did talk to another gentleman who had a 4 cam shroud mated to a 356 motor. He drove his 356 up a hill and the motor burned up. He removed the shroud, plopped in a new 356 motor with the original shroud and went on his way. He never did much to investigate this failure.
My recommendation: stay away. Sure it looks cool, but I don’t think it is worth $15,000 and a burned up motor.
Anand
Anything is possible, I suppose, but there you go.
A volute ("venturi ring") makes a lot more sense in maximizing airflow. They're readily available from awesomepowdercoat.com.
I bought a hubcap and cut it and messed about a bit. Never tried running the car with the cone in the fan because it was never secured by more than a threaded rod and a nut. Balancing it to stay smooth (and stay put) at 7,500 RPM was going to exceed my abilities, so I asked my machinist friend who is also into VW stuff.
He considered the issues and bowed out, and that was that.
Were I to try again I would start with a model airplane prop cone instead of a wheel cover. Those are much lighter and run very high RPM so it'd be down to attaching it.
All that said, see @arajani and @Stan Galat's comments.
Andrig, as some if you know, has been messing with cooling options forever. Unfortunately, he took his double-sided Gen 2 fan off the market after a few folks experienced failures, and he’s looking to re-introduce it with a metal/3D printed hybrid.
https://www.facebook.com/10006...43/?__so__=permalink
@edsnova posted:I bought a hubcap and cut it and messed about a bit. Never tried running the car with the cone in the fan because it was never secured by more than a threaded rod and a nut. Balancing it to stay smooth (and stay put) at 7,500 RPM was going to exceed my abilities, so I asked my machinist friend who is also into VW stuff.
He considered the issues and bowed out, and that was that.
Were I to try again I would start with a model airplane prop cone instead of a wheel cover. Those are much lighter and run very high RPM so it's be down to attaching it.
All that said, see @arajani and @Stan Galat's comments.
I think if I attempted something like this, I would make a new fan nut, with a raised external thread about 1” OD. Then I would turn a cone out of 3” aluminum bar stock, thread internally, and screw it on. I would also bore behind the thread, removing some more weight from the cone. I think this would have very minimal effect, if any, on balance.
The question I have is, does this really do anything to increase airflow?
The 4 cam was one of the most iconic engines of all times. Heck James Dean died running a 4 cam. And I get it people would love to have an engine that looks like a 4 cam. But these are replicas. I know my Subaru Spyder is lame but I’ve had a Spyder with a type 1 running a 911 shroud and I now have a Conv D with a type 4 running a 911 shroud. And they also cool really well. It’s ok to use something that looks great and is pure Porsche and that functions great.
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@LI-Rick posted:....The question I have is, does this really do anything to increase airflow?
Well, everyone else seems to have an opinion on this without really knowing much about the engineering involved, so why shouldn't I?
First, most of us do know that VW and Porsche engineers did take the matter of airflow and cooling pretty seriously. Much has been written about how carefully the design of shrouds, cooling tins, and fan blades was researched.
Second, it's also pretty well known that the VW/356 fan stops being efficient above a certain speed (I think that's about 4000 rpm, but I could be wrong).
Third, if the 356 fan could have been made to work on the four-cam engine, those very practical dudes wouldn't have wasted time engineering a whole new fan for it. They obviously needed a new fan design for a racing engine that was going to spend most of it's time between 6000 and 8000 rpm.
Fourth, it's also pretty likely that a fan designed to work best at those higher speeds wouldn't be very efficient at all down at the speeds that our engines like.
So, I'm thinking, as cool as the four-cam fan looks, we shouldn't be too surprised that most attempts to make one work on our engines have been total failures.
I think I'm just going to ask the AI bot to make me a photo of my car with a Fuhrman engine showing out the back, stick that up on the wall over my computer screen, and move on.
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@Sacto Mitch, I agree with all of the above.
I probably wasn’t as clear as I could have been, but this discussion was about the cone in the center of the fan itself. We would need an expert in fluid dynamics to explain to us plebeians the folly of pursuing such an endeavor.
AFAIK, there’s more data about the effects of a Venturi ring than any sort of nose cone.
https://www.awesomepowdercoat.com/vw-venturi-rings
@dlearl476 posted:AFAIK, there’s more data about the effects of a Venturi ring that any sort of nose cone.
https://www.awesomepowdercoat.com/vw-venturi-rings
Where Clark got his data is anyone’s guess. I had one dealing with him. I was less then impressed by his customer service or his quality assurance.
Let's research this. A nose cone for a radial fan seems to be an unusual thing. If you start searching you end up with a lot of this; but not so much that looks like a Carrera engine.
"Cone for radial fan" returns a lot of examples of the venturi ring which is available sized to order for cheap if one wishes to start messing around, (as well as a bolt-on application as linked above).
There is one tech article and patent application, but when you examine it, it looks more like a nose cone for an axial fan. That's not what most of us are running.
In conclusion: the immediately available evidence on der innerweb suggests that affixing a cool-looking bullet nosecone in the shadowy voids of our stock Beetle-type fans would do them no good, function-wise, and might probably hinder their function.
Thanks Ed for researching that,
I have no idea what works , but why is the "cone" on the 4 cam motor if its not helping , German engineers were trying to do something , and it was not on any 356 pushrod motor I have ever seen ..... Ummmm
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Excerpt from an article by Karl Ludvigsen on the Fuhrmann engine.
Cool stuff about the fan, but no specifics about the central cone. One key point, though, is that the design of the fan was critical enough that Fuhrmann consulted one of the air-cooled engineers who had helped develop the original VW engine but was no longer with Porsche at the time (although he later returned).
And, as I suspected, it looks like choosing the right rotating speed for the fan was crucial.
"Arranging adequate air cooling for the heads of this high performance engine posed a major problem. Air would not flow downward with equal force over the seats and ports of both inlet and exhaust valves as it did in the other Porsche engines. It would, instead, pick up heat from the upper, inlet side of the head before continuing downward to cool the even hotter exhaust-valve area.
This situation was acceptable to Fuhrmann because he wanted the inlet side of the engine to be cool to maintain high volumetric efficiency for best power. Total cooling-fin area was increased from 2600 square inches on the normal Porsche engines to 3600 on the Type 547, most of the increase accounted for by the cylinder heads.
For a suitable cooling blower for his engine Fuhrmann drew on the knowledge of an expert in the design of air-cooled engines, Franz Xaver Reimspiess. After 1945 Reimspiess had gone to work for Steyr in Austria before re-joining Porsche in Zuffenhausen in 1951. There he developed and patented the type of dual-fan blower chosen for the Type 547, which needed efficient, low-drag cooling with a large volume of air flow at high crankshaft speeds.
The fan was of radial-outflow design with backward-curved blades, the most efficient blade design although also the most space-consuming. The fan was large enough to be doublesided, drawing air from both front and back of the engine. The generator acted as the fan-drive shaft and support. Front and back sections of the fan fed completely separate cooling ducts to the front and rear opposing cylinder pairs of the engine.
Instead of the square edges that a production design would dictate, the aluminium fan shrouds were given smooth curves that enhanced airflow both internally and at the equally important entries to the fans. Efficiency was also enhanced by moderating the fan speed. Drive belts of the pushrod 1.5-litre engines turned the fan at 1.8 times crankshaft speed, or 9000 rpm when the engine was turning 5000. The Type 547 engine was given a one-to-one pulley ratio so its fan was spinning at only 7000rpm when the engine was revving that high.
These subtle touches added up to a fan and shroud system that could pump almost twice as much air as the Porsche 1500 blower while demanding only slightly more power to do it. At 7300 rpm the Type 547 fan needed 8.8 horsepower to drive it and delivered 2750 cubic feet of air per minute. Even at the lower speed of 6200rpm the Type 547 blower was still delivering 2330 cubic feet per minute while absorbing 6.0 drive horsepower. The moderate horsepower requirement meant that this exotic engine’s fan could still be driven by a simple vee-belt. "
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@LI-Rick posted:Where Clark got his data is anyone’s guess. I had one dealing with him. I was less then impressed by his customer service or his quality assurance.
He got it from Andrig, who’s been working on a double sided fan as well. He quotes it in the link.
Shame you had problems with Clark. He was nothing but helpful to me.
@edsnova posted:"Cone for radial fan" returns a lot of examples of the venturi ring which is available sized to order for cheap if one wishes to start messing around, (as well as a bolt-on application as linked above)
No need to mess around. The VW engineers already did.
https://store.concept1.ca/Fan-...es-COOLED.1.2-62217/
I have since sold the car, but this was my attempt at a 4 cam shroud. Because of the larger fan and external oil cooler, it worked great.
That's outrageously cool, David. Thanks for finding and posting it.
OK gonna revive this with an interesting tech article I ran across re VW fan efficiency and speed.
Nothing here about a nose cone or velocity ring, but a pretty solid breakdown of the engineering of this thing and its limits.
tl,dr:
A. The 1.8(ish) drive ratio does not make our fans turn 8000 rpm. What happens is the V-belt slips, and the fan does not exceed about 5-6000.
B. The fans we use do not "stall" or lose efficiency as they spin faster. They simply cease spinning faster (see A, above).
C. Slower fan speeds (as with a "power pulley") DO decrease airflow, but they decrease cooling less than is commonly thought, and they decrease the amount of power used by the fan by more than you'd probably imagine.
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That was a great article, Ed.
It had some fascinating information for geeks like me who like that kind of stuff. I say 'fascinating' rather than useful because most of us will just accept the advice of guys who have been working on these engines for years in their shops and garages. Those dudes have usually arrived at the same conclusions as the engineers without doing all the math and may even come up with practical solutions that work even though the engineers have no explanations for why they do.
And in a way, it's a little deflating finding out all these great-sounding theories one has been passing on as fact for years are entirely without foundation. Some things you just don't want to know.
Folklore is an important part of this hobby.
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@Sacto Mitch posted:.
That was a great article, Ed.
Folklore is an important part of this hobby.
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Folklore and old wives tales are a VERY annoying part of this hobby for me.
Also, see "you can't do that" or "you'll never get it back together" or my favorite "you'll have parts left over".
My absolute favorite though: "You can't rebuild a VW transmission at home".
WRONG!!!
Looking forward to reading this article later. Thanks, Ed.
"Folklore is an important part of this hobby."
Or just about ANY hobby.
One of my work colleagues came up with the term "RFI"
"Rumor, Folklore and Innuendo."
We used to hear a lot of that and fought it just about every day.
@Gordon Nichols posted:"Folklore is an important part of this hobby."
Or just about ANY hobby.
One of my work colleagues came up with the term "RFI"
"Rumor, Folklore and Innuendo."
We used to hear a lot of that and fought it just about every day.
In my world it means radio frequency interference. Ever heard that version?
@Gordon Nichols posted:"Rumor, Folklore and Innuendo."
In our business, we call it "folklore and common knowledge" when information is just plainly anecdotal BS.
@DannyP posted:In my world it means radio frequency interference. Ever heard that version?
Absolutely, and especially back in the early 1980's when the RFI regulations on computers were tightened up - A lot - because of the anticipated wave of upcoming cell phones, RF TV remotes, Garage door openers, all sorts of radio devices. That's when Balun cores started showing up on electronic device AC cords all over the place to keep circuit noise out of the local AC system, and mucho dinero was spent on "hardening" all sorts of things from doorbells to TVs to computers. We've taken a much more sophisticated approach since those wild west days but a lot of design cycles are spent on minimizing radio interference, especially at the frequencies used by household WiFi routers (and most computers).
Back around 1980, the computers from my company were, um...., noisy to say the least, but so were everyone else's. There was an RFI Hired-Gun-Guru from the West Coast that we hired to come in and test our stuff and then recommend fixes to minimize the noise. The first thing he told us to do after he sniffed the RF spectrum on our refrigerator-sized system was,
"Go to the Cafeteria and get one of the largest rolls of heavy Aluminum foil you can find. We're gonna need a lot to wrap this baby up!"
His work, and our subsequent re-designs, put the computer cards in closed metal boxes with all input/output lines run through radio frequency chokes of various designs to manage the noise. It was a BIG FRIGGIN DEAL to say the least. Lots have changed in the decades since, for sure. Now, for example, a lot of shielding is done right on the circuit boards, the card cage is closed a lot less than before and you can run shielded CAT-X cables without fear of picking up spurious noise along the run, sometimes over hundreds+ feet.
Ahhh.... The Wild West Days of early Mini-Computers!
What I knew of as RFI was mostly in reference to do with the Sennheiser wireless microphone racks. I was never a specific radio guy on a tour but I still ended up doing it/helping with setting it up. One or two handhelds it’s pretty easy, but the 25-30 frequency headset/Tx/Rx set ups, along with the crew’s walkie talkies, it sometimes took a bit of juggling to avoid all the TV, radio, and EMS frequencies.
