Dual fan housing?

[Alexander_Monday]

I am working on a set up to install an mc-80 supercharger on a type 1.  I still need to get the front drive used on the scirroco in the 80's, however the blower itself is in perfect condition.  One thing I need is room to install it.  It will just clear the firewall if the fan housing was not in the way.  I have conceived of a dual fan housing using 2 alternators and fans.  They and the blower would be driven by a serpentine belt with idler pulleys. 

Just wondering if anyone could tell me if I am crazy for trying this?  Would the right volute be anywhere near as efficient as the left one?

[vwracer3]

I saw something very similar to this several years ago.  This car was green and was running a long snout supercharger.  He did what you are talking about and ran a custom fan shroud with two fans with the supercharger in the middle.  If I remeber corectly he had an alternator on one side and the other side was just a shaft to the fan.... it looked good and he said that it worked well.. his oil cooler was external with an electric fan...

[vwracer3]

i just found the pic of the car I was talking about...

http://www.thesamba.com/vw/forum/album_page.php?pic_id=743

[Alexander_Monday]

i just found the pic of the car I was talking about...

http://www.thesamba.com/vw/forum/album_page.php?pic_id=743

Thank you very much,  that is exactly what I envisioned.  Am sending email to picture poster to see if they know who did this so I can contact them.

[HotrodVW]

That's badd ass!   

[ctach]

Cool idea but it takes a lot of ponies to run the belts, and what do you get in return?  Better off going Turbo, free horsepower.

[JVance]

In return, you get to do something different.

Some people do it because they enjoy the challenge of fabricating something that previously did not exist...and if it works, then the satisfaction is what you get in return. Bolt-on DLI supercharger? I care as much about that as a CB Performance hide-away turbo set up (no offense, CB). Custom supercharger set-up? Pretty wicked, irregardless of whether you could've done it with a turbo.

[Alexander_Monday]

That's badd ass!   

Thats why.

This is a street car, and fast VW's around here are few and far between.  This is the first bug I have built.  I built my street sand rail in
'88 and have went mid 11's with it.  The basically same engine in the bug seems to be a high 12 or low 13 by comparison, however I did build
it with low compression with the antiquated roots blower in mind to make up the lb/hp deficit. I am not happy with high 12's, as there are
quite a few v8's around, a few rice burners, and at least 1 rotary that would easily snack on me currently.  There are a couple of big turbo VW's
that are faster than mid 11's, however I would have to have much better heads, and quite a bit more cc's than 2110 to compete.
I have thought of going turbo, and yes I agree the power efficiency is better, and have talked to a 2 locals who have big turbo engines.
However, in the 70's when I cut my teeth with the high performance street scene, if it had a roots blower it was bad a$$, and I don't
see a problem with getting it in the 11's with 8 to 10 lb of boost.  Maybe I am just a dinosaur in that respect?


Unfortunately the person that posted the pic on the Samba said "It belonged to a kid from Fresno and it's been at least 10 years ago now so
no current info is available." 

So, if anyone knows more about that green VW from Fresno about 10 years ago, please let me know.
I also need a front cover drive like the 80's Scirocco MC80 blower kit that Autotech sold.  As I understand it, Jerry Magnuson made the blower,
however sold the dies and parts to a drag bike racer that died at the track.  They currently are in the possession of Magnacharger,
( http://www.magnacharger.net/ ) but he apparently has no interest in helping me out, so if anyone can help me out there, it would be appreciated also. 

[Jake Raby]

The problem with a second fan placed on the left side of the shroud is actually being able to direct it's air effectively. Years ago the guys at MSHP made up one of these and sent it to me for testing, the arrangement was a real hodge podge and didn't do anything for the engine except pull power...

The reason for that is the fact that the tangential clockwise flow coming off the left side fan just wants to blow on top of the engine case, without enough room in the shroud to manipulate that air back counterclosckwise and down to the 3-4 cylinder heads.

The VW factory positioned the stock fan in a critical position on the right side of the engine- they needed the added real estate inside the shroud to place the air foils and diverters needed to boost pressure back to the left side cylinders. This is why the center mounted aftermarket shrouds that have no room for internal vanes are engine killers....

Air is a funny thing, not many things within the cooling system function the way our minds think they do- I learned that years ago.

[jeff denham]

very well said stripped 66.build it alexander!. very cool indeed. its always a pleasure to sweat for HP and TORQE in a ACVW you would have well earned the satisfaction . i wish you good luck on your project hope everything works out for ya. jeff d.

[Mark Harney]

The problem with a second fan placed on the left side of the shroud is actually being able to direct it's air effectively. Years ago the guys at MSHP made up one of these and sent it to me for testing, the arrangement was a real hodge podge and didn't do anything for the engine except pull power...

The reason for that is the fact that the tangential clockwise flow coming off the left side fan just wants to blow on top of the engine case, without enough room in the shroud to manipulate that air back counterclosckwise and down to the 3-4 cylinder heads.

The VW factory positioned the stock fan in a critical position on the right side of the engine- they needed the added real estate inside the shroud to place the air foils and diverters needed to boost pressure back to the left side cylinders. This is why the center mounted aftermarket shrouds that have no room for internal vanes are engine killers....

Air is a funny thing, not many things within the cooling system function the way our minds think they do- I learned that years ago.

This is correct.  Now if you could have an opposite fan made, and find a good way to reverse the spin (back side of a belt, for instance), you might have something.  There are double sided belts made.

[Eaallred]

Just run E85 and eliminate the cooling shrouds completley. Done and done. 

[Alexander_Monday]

Air is a funny thing, not many things within the cooling system function the way our minds think they do- I learned that years ago.

Jake, 

  At first I thought I was thinking left and right backwards from you, however your mention of the stock fan being on the right side
tells me we are calling the same things left and right.

  That is interesting. I would have thought that directing the right side to flow down would have been the problem, as the
left side in my drawing is almost the same layout as a commercial fan arrangement, whereas I had to modify the right side quite
a bit to try to redirect the flow down and keep the center of the fan far enough to the right to keep space in the middle.

 

[Jake Raby]

The drawings are hypothetical..  Build it and get results and you'll see that the drawings are not very relative to the results.
 Plenum volume is key to most everything, in fact unil I modified the size of my left side upper plenum on the DTM I wasn't able to make it work very well at all..

Space is the issue...

And don't forget that now you'll have a second fan robbing air from the engine bay as well as the carbs.. Cooling systems can't function if the engine bay lacks an adequate charge of air.. I determined that the pre 67 engine bay would barely sustain a set of 44mm IDF carbs and one stock TI cooling fan...

These are just some of the things that will impact your endeavors and if your desires for total success are as high as mine- it will drive you crazy and control your dreams and every thought for weeks on end..Nothing drives me more crazy that cooling system development..

[gonebuggy]

You should make up two fans that are 50% smaller, because otherwise you double many things. Thuings like: double the output of the cooling system, double the loss of horsepower to power them.

Things to ponder,

Alex

[Alexander_Monday]

And don't forget that now you'll have a second fan robbing air from the engine bay as well as the carbs.. Cooling systems can't function if the engine bay lacks an adequate charge of air.

You should make up two fans that are 50% smaller, because otherwise you double many things. Thuings like: double the output of the cooling system, double the loss of horsepower to power them.

I was going to use stock fans because this is just one more thing that I will not have to create. Also this would allow me to cut out the pressed areas on the intake side of a couple of shrouds  that match the fan profile.  If I were to use smaller fans I think they would need to be somewhere between 50 & 100 percent, as 50% physically would probably give less than 50% of the air.  I was planning on varying the pully size according to the air flow needed. 

These are just some of the things that will impact your endeavors and if your desires for total success are as high as mine- it will drive you crazy and control your dreams and every thought for weeks on end..Nothing drives me more crazy that cooling system development..

I have thought about this for over a year, but have been hesitant to build it due to the great amount of unknowns involved.  It is good to know that someone else has done it, although I wish I could contact them to find out if their's cooled good enough.  On the other hand, if someone who has done as much research as Jake sees basic design flaws it makes me a little hesitant because I also have one of those personalities that will be driven crazy to make it work once I start on it.

Bottom line is that without the front drive for the supercharger it will be a moot point to build it because I could no longer use dual webbers and would not have the supercharger to make the additional power I want.  Turbo is the alternative, but I still like the idea of a roots blower.

Thank you all for interjecting your ideas.  I am going to build it in any spare time I have, however until I get the supercharger front drive it will be a back burner project.

[fast54vw]

will the added power from the blower make up for the HP loss from 2 fans?

[Alexander_Monday]

will the added power from the blower make up for the HP loss from 2 fans?

  I plan to turn the fans slower than stock.  If the designed volutes (snail shaped area between the green and purple lines) are efficient at all, the 2 fans should not take much more power than 1 stock one because they will be turning at a slower speed and could actually take less.  I am aware that losses could be somewhat higher because there should be more eddies and votices (wasted circular motion like you see at an airplanes wingtips), however a tangential outlet fan (the classic centrifugal fan like a furnace blower) normally has a higher efficiency than an open design (the vw doghouse is kind of in between) so they might actually take less power.  There are a couple of different design rules of thumb.  I have chosen to make the volute cross section increase at a linear rate (a so called CAM design) because it has a lower pressure variation across the outlet compared to a logarithmic increase in cross section.  As Jake said though, when it comes to complicated fluid dynamics it does not always work the way one would intuitively think.  Unfortunately I do not have the mega expensive computational fluid dynamics software that is needed to simulate it. 
  I plan to use a serpentine ribbed belt to drive both fans and the supercharger in an effort to try and lower the up force created on the crank pulley.  I know there will be some additional loss from the serpentine ribbed arraignment compared to the simple stock v belt.
  I am also aware that a roots style blower is not a very efficient thing in and of itself, and that is why a properly designed tubo engine will make more hp/btu of fuel, but I am not looking for the greatest efficiency.

  All I can do is try it and find out.

[marty hiskey]

i wanted to do this for awhile now but instead of using a roots style blower i was looking into centrifugal type blower from vortech. they where willing to give me a hogged out blower for $100 bucks to moch up the brackets. i was going to do a blow through system using a c.b. performance turbo blow through components for the tubes to the carbs. vortech said if i was able to make it work with good results they would probably be interested in making a kit off my setup. what about using electric fans and using one of those small high amp alternators that some guys use on race cars.

[Alexander_Monday]

i wanted to do this for awhile now but instead of using a roots style blower i was looking into centrifugal type blower from vortech. they where willing to give me a hogged out blower for $100 bucks to moch up the brackets. i was going to do a blow through system using a c.b. performance turbo blow through components for the tubes to the carbs. vortech said if i was able to make it work with good results they would probably be interested in making a kit off my setup. what about using electric fans and using one of those small high amp alternators that some guys use on race cars.

  I also thought about a centrifugal supercharger because it should be able to be incorporated with the stock doghouse in place, however the old time hot rodder in me wants a roots type.  The DLI kit is engineered with the doghouse in place, however there is no way you could get a "hood" on the car, not to mention the stories I have read about delivery time.

  Unfortunately the numbers do not look good for using an alternator motor combo to drive cooling fans.   At 100% efficiency  1 horsepower = 746 watts,  746 watts = 13 Volts X 57 Amps.  Given 80% efficiency for the electric motors and you need 71 Amps per hp.  I am unsure of the hp required, however lets say 6 hp total.  You would need 430 Amps @ 71 Amps / hp.  This is impractical and given that most alternators are in the range of 55% efficient you would need 13.5 hp input to the alternator to produce 6 hp worth of fan spinning, not to mention the 7.5 hp worth of wasted heat put into the engine compartment.

[jeremy]

I've thought about this myself. That Fast Fiat had an interesting fan set up. Two electric fans sitting flat adapted to stock tin I think. Looked pretty low profile. I tried to find some pics but unsuccessful. If you could fab some sort of intake I would think you would have enough room in the engine bay. Maybe someone else could find some pics.

Jeremy

[Jake Raby]

Electric fans are fine for race situations at the fdrag strip.. On the street the added BTU output os a solid sustained load will overcome them pretty easily..

Adding more alternator power to compensate also is a HP loss, as there is always a trade off with power... Fans use energy and there is no way around it without using a 2 cycle weed eater engine to turn your fans (yes I have done that)..

[NoBars]

The bike guy that died was probably Elmer Trett.

check out autorotor.

[NoBars]

A newer Mini Cooper OEM supercharger would probably be great for your application.

[FITNESSFORYOUTOO]

There is a street Fiat on here (fast fiat) with dual electric fans and it runs in the 9's and you could always turn them off for the pass then at the end flip the switch back on. So your HP loss issue is not an issue at all.

[Tate]

He wants to build a street car, not a drag car.  I think being different is cool, but this seems like a lot of work for what you are possibly gaining.  But I do remember loving (in the 80's)  a big roots supercharger sticking out of a Malibu hood.   

[Alexander_Monday]

Well, it has been a while, but I have been busy slowly woking on it.  The MC80 roots blower has been put aside and a more efficient Autorotor 3150 twin screw has been used.

The problem with a second fan placed on the left side of the shroud is actually being able to direct it's air effectively.  .......... The reason for that is the fact that the tangential clockwise flow coming off the left side fan just wants to blow on top of the engine case, without enough room in the shroud to manipulate that air back counterclosckwise and down to the 3-4 cylinder heads.   .........    Air is a funny thing, not many things within the cooling system function the way our minds think they do- I learned that years ago.

The drawings are hypothetical..  Build it and get results and you'll see that the drawings are not very relative to the results.

I have found that the left shroud has a very even output across the exit opening, however the right shroud has more flow inside and outside than in the middle.   The left side seems the same with and without flaps, however the addition of flaps on the right side increases the "hole" in the middle.  A quick check with a cardboard deflector added shows me that I can even out the right side with deflectors.

Question is should it be even across or should the air flow be biased to one area or areas?  

Jake?

[jgerock]

Interesting concept!  

Sorry for a partial hi-jack.. although I have seen a picture of a dual-fan in an older VW magazine.  I'll try to find and scan it.

When I saw the topic, I first thought someone had adapted or constructed the dual air inlet fan shroud from a Porsche Carrera engine.  I have always wondered if someone would do this on a hi-po street VW engine that has dual carbs stealing most of the cooling air from the rear fan air entrance.

I believe the Carrera fan housing has an air entrance on both the front and rear sides of the shroud, but I've never seen the interior details.
 

[bowen71]

Interesting concept! 

Sorry for a partial hi-jack.. although I have seen a picture of a dual-fan in an older VW magazine.  I'll try to find and scan it.

When I saw the topic, I first thought someone had adapted or constructed the dual air inlet fan shroud from a Porsche Carrera engine.  I have always wondered if someone would do this on a hi-po street VW engine that has dual carbs stealing most of the cooling air from the rear fan air entrance.

I believe the Carrera fan housing has an air entrance on both the front and rear sides of the shroud, but I've never seen the interior details.
 

Thats all good but, He cant get a supercharger in the middle with that setup.

[jgerock]

Thats all good but, He cant get a supercharger in the middle with that setup.

You are right - but...
I described why I included the Carrera information and said I was sorry for hi-jacking the thread.  I realize a supercharger wouldn't fit where the center-mount shroud is located.   I did start looking for a picture for the twin shrouds.   

[Ohio Tom (DdK)]

Use some old 36hp fans, they are thinner and only have 16 blades...
This is an old Formula Vee trick to minimize HP losses.

[elmo]

I think if someone came out with a Carrera shroud- that works at least as good as a stock doghouse- it would be a really big hit.

[Donny B.]

I thought Jake was working on one a while back.  Perhaps he will chime in...