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Mr.ElectWizard March 27th 2003 18:00

911 Fan Shroud
What size engine would merit using a 911 fan shroud? And which oil cooler do you suggest using?

Mr.Elect.Wizard April 14th 2003 13:37

I know that a stock TIV wouldn't need one. Might overcool the motor, so are they not necessary until you get into the 2.2L range?

vujade April 14th 2003 13:46

Mr ElectWizard
are you just requoting someone or are these your findings?

I have seen many smaller motors using these shrouds and have never heard of it damaging anyones motor.

And according to Jakes new findings they may not cool as much as thought previosly.

Massive Type IV April 14th 2003 16:05

Heck, in my findings they are not needed at all. Mostly they are used for cosmetics.

I only have one version of an engine smaller than a 2270 that uses one.

Last week I built 2 identical engines, one was for a 914, the other was for a Bug with the 911 shroud. With the EXACT same settings the STOCK cooled engine COOLED BETTER!

Test was done on the same day, same weather, hell I even used the same distributor and same carbs. I have witnesses, one of which now does not want the 911 shroud on his engine!!!

Alex April 14th 2003 19:04

Disclaimer: This is not intended to p*** anybody off but I thought the additional info should be posted:

Hi Jake,

when ever the 911 shroud is mentioned I feel that I am a total idiot for using one because of looks.

First of all:

All the years before the entire North American VW scene said that they overcool the engine. Now it is being said that they do not cool as good as stock. I am not doubting your findings at all but it is kind of strange that they do the opposite of what was said before.

Also this findings could have several reasons:

Shroud design and/ or the fan blade that was used.

To my knowledge there are several manufacturers of 911 cooling kits: MSS (CSP/WEISER etc), PTP, Remmele, Klaus, WILKE, WILLIBALD, CIP, Bergmann, Sharbuilt, FAT
I am sure I forgot quite a few. Also there are 3 different Porsche fans that can be used:5 blade, 11 blade and the 12 blade C2 fan

The 11 blade fan came in 2 sizes.....911 Turbo used a smaller one.
There are copies of fans that are made by the manufactures of the 911 least some of them do it.

Golf alternators or Porsche ones are used too.

The kits also come in 4 different fan ring sizes. If you shuffle this with the different shroud designs I can not believe that they are all junk. I know your opinion and you know mine. Your finding was quite interesting but it would be more interesting if a FAT, Sharpbuilt and other kits were used as well in that testing. I know that the one you tested was put on one of your engines before and you were not impressed which btw I could totally understand why.

The point I am trying to make now is will everybody say now that the shrouds do NOT cool as good as stock?

The C2 fan produces the smallest amout of air followed by the 11 blade and the best is the 5 blade. If you turn down the C2 fan to the small size to fit all the small 240 911 kits you lose 40% of effectiveness (Tested by Rolf Klaus) which is not true if you use the small version of the 11 blade fan that Porsche used in the 911 Turbo.


An interesting point too is that you can get a 911 kit complete with 911 alternator/ring and fan for 600$ FAT ( 3??$ for shourd kit and the rest for used Porsche parts and no machining of the case) if you are lucky so they are not that expensive too.

Alex April 14th 2003 19:30

I also would like to mention that I do not doubt the effectiveness of the DTM or Jakes new shroud.

This is only geared towards the 911 cooling kits.


Massive Type IV April 14th 2003 21:38

I have nothing more to say. I know what I see time after time. I know what I saw in that test (which was actually never intended to be a test)

I will stand my ground with this, but will not let it grow into another argumant that gets people mad.

Things that contradict conventional wisdom stir up alot of questions, and start arguments.

Alex knows the truth about a certain component that would send people reeling if I were to share what my experiences with it were......

No more time for arguments.

Wally April 15th 2003 05:17

Now I get really curious. Would that be the under-cylinder cooling tin?
(you may also let me know this by privat e-mail)

oasis April 15th 2003 11:54

I'm kinda curious with this thread about one thing ... are these the opinions and observations surrounding the 2056 and 2270 engines only, or are they universal (including the 2563)?


Massive Type IV April 15th 2003 13:39

In my observation, engine size has no affect on the results, however the combinations of parts do...

I know it seems outlandish, and hard to believe but I'm considering not using any 911 cooling systems in the future. My customer base is mainly comprised of people who take practicality and performance over cosmetics.

factman April 15th 2003 19:20

not to stir up an argument but i think it needs to be noted that you(Jake) use the 911 kit on only one engine and that is because you need to make the heat for the fan to be needed. so does the fan overcool or undercool? i dont know about all the variations of this kit but it seems like if you have to create heat a.k.a more compression, headwork, cam, and others, then it sounds like the 911 kit cools too good for use on the average motor. just my thoughts on the matter. thanks guys.

Massive Type IV April 15th 2003 19:31

This particular engine was different!

The customer originally had purchased a DTM kit, the order was never filled(just like alot of others).

The customer had to make his mind up so we ended up splitting the case again and machining for the 911 fan. The engine combo was already assembled, so it had to stay the same as any other version C. The 2 engines in question had the same deck height, same head cc, same valve margins, same cam, same everything. Looking at the specs all I can see that was different was the rod side clearances and the pushrod length (which is rarely the same) we netted the same valve lifts and the works!

This engine was directly tested against another 2270 Version C oon the same day, same dyno, same tank of fuel and same operator. We never even planned it that way till we decided to do the back to back testing.

There was no other changes,neither overheated, but one did stay much cooler, and thats not the one with the huge fan.

More air is not the answer, efficiently routed air, is..... believe me if you want, come watch me and you will doubt no more.

vujade April 16th 2003 08:42


I dont think anyone here is doubting your findings.

I do believe that any successful company in this day & age
would have to do many conclusive tests before publishing their findings.

Could you imagine is Pfizer only tested Viagra on 1 person?
Would anyone be willing to risk their life using their product?

Or what if GM only did one road test with their Corvette?
Would anyone spend $50,000 on a Corvette if they werent sure that it could accelerate or stop as fast as the manufacturer has claimed?

From what I have gathered on the net, their is not enough conclusive evidence not to use the 911 Shroud on any size engine.

Sandeep April 16th 2003 10:08


I'm holding out on an engine right now because of all of the promising developments in the Type 4 world.

The development of your 2316cc BEAST is amazing as is LN Engineering's new heads.

I'm budgeting for an 80mm x 100mm (Biral Babies) based engine with LN's new heads (2513cc). I'm looking for a mid-performer, not a screamer, with the potential to upgrade to a screamer.

I understand that this type of engine might run as cool as a stocker. What do you think would be the cooling requirements for this type of engine ? Would the 911 fan be overkill ?



Massive Type IV April 16th 2003 11:04

I'm finding that it may be overkill for about any engine.

See, what I say defys conventional wisdom.

I will never absolutely publish that the system does not work, but when I feel strongly enough about it to refuse to use any of them on any of my engines (just like hydro lifters) people should realize that what I found was conclusive enough! I have been noticing this for years, not since yesterday. Both in the car, and on the dyno.

People spend their money the wrong engine is not about cosmetics, or "Sounding good at idle"....when people quit letting the nonsense fact that their engine has to look like a 911 engine to cool, they will figure out the first big step in the road to successful power.

I could have been like everyone else, and made a 911 shroud, instead of my knockoff of the DTM. The molds would have cost 3 times less, as the shroud is one pices, and the casting is very simple. The 911 shroud would have sold like mad to people that want their engine to "Look" like a 911....

I have a new idea, if you want it to look like a 911, just make a 911 engine fit in the engine bay! The result would be something that actually works, has the looks, and the power to boot. Be ready to spend atleast 12K to do it right!

Sandeep April 16th 2003 11:52

I understand what you are saying Jake.

One good thing about the 911 kit is that there is a market for it out there, and if I decide to get rid of mine in the future, I'm sure I could sell it.

When it comes time for me to put my engine together, I will arrange to come down to Georgia to see your opereration. I understand that is takes a combination of parts to acheive a goal and I am all for that. I just have to wait for the 100mm Birals to come into production as well as LN's new heads.

My end goal is to race my beetle locally in a GT3 class in a couple of years (pure race car) so cosmetics will not be an issue then. Looking forward to it.



Massive Type IV April 16th 2003 13:46

The LN heads will be awesome.....The first set being sold are coming to my shop for a 2615 engine...

Unregistered April 16th 2003 19:05

I think what folks want to know is does a 911 setup overcool


" There was no other changes,neither overheated, but one did stay much cooler, and thats not the one with the huge fan."

Alex and Vujade both speak wisely on the subject

There will be no argument, if we all know under what circumstances these products are being tested and what is meant by "cools better" does the DTM have a thermostat?

Massive Type IV April 16th 2003 19:21

Like I said.....Neither overheated, The DTM cooled 20 degrees better, thats all....

Unregistered April 16th 2003 19:27

So 911 fans don't overcool?

Massive Type IV April 16th 2003 19:44

Nothing overcools on the dyno............

factman April 16th 2003 19:55

i see your point with saying that its not how much air you have but how you direct it and that is true of the 911 fan as it does not direct its air in any particular place but down. my attraction to the fan is a resolve for changing my spark plugs withough pulling my carbs off. that really sucks and i have pretty big hands so i can even get to all my carb bolts. so until i make some tools that make it so i can do it on my own i might still get the 911 fan. yeah call me a pansy but i like to do things fast. and if anyone has an answer the spark plug problem then tell me about it. i have a T1 not a T4 . thanks again guys.

PIOMAC April 18th 2003 23:53

Cosmetics is not the only reason for the 911 set-up. I am placing a T4 2L with the Fat upright conversion in my 67 bus. When I got the bus th3 T4 was aleady in there, but the Prev. owner had to fabricate a rear apron so that the engine deck lid would close. Now that I have the uright conversion, I will be able to utilize the original rear apron and be able to close the engine decklid. Now if I can only figure out how to fit an exhaust underneath the original rear bumper:confused:

PIOMAC April 18th 2003 23:55

I forgot to mention that with the previous setup, that the engine decklid did close but NOT properly. Now it will close properly with the upright conversion.

sparkmaster1 April 19th 2003 00:23

"Looks" really doesn't matter when you don't have to open the decklid every 200 miles like on "some" a/c performance engines. Kind of like chrome, it won't get you home. I'll take pratical, well thought out parts over shiny ohh, ahh parts any day. Tim

57mutant April 19th 2003 10:09

No longer confused
So, having re-read this thread numerous times, the final conclusion is that the 911 fan/shroud neither overcools or undercools. It does the job its intended to. So it is functional. It also has a cosmetic appeal to certain people - this is the German Look Forum is it not. Even though they are functional, I favor Sparco seats and Momo steering wheels over the original items. So too are the original brakes, suspension and wheels functional. But again I prefer the upgraded Porche alternatives that I associated with the German Look. So what's wrong with functional and good looking? To me, that's what the "Look" is all about.

vujade April 19th 2003 10:19

I agree complete 57mutant.
Some people dont see it that way.

Ron Roberts April 19th 2003 12:37

There are alot of variables here. There are different 911 fans. Also there are different 911 style shrouds. Also there are different engines but If I understand correctly that is not the issue.

Jake, Does your recent findings make it logical to use the DTM on your 2270 D, or are there still factors that continue to make that particular 911 shroud the best choice for that engine? I realize the DTM is somewhat a mute point now that it is no longer the DTM that we all know. (Assuming your DTM will have some modifiations of the old).



Mr.Elect.Wizard April 21st 2003 12:06

forget about this thread for a week or so, and it blows up... This is exactly the type of replies I was looking for... Yes, the 911 shroud looks pretty bad a$$, but if there are alternatives such as the DTM (or Jake's) that work better than so be it, I'd probably still go with one of Jake's...
Glad to see that there were no major fires started in this thread...
Jake, still hope I can experience one of these MassIVe motors some day...

Massive Type IV April 21st 2003 19:01

My concensus:

spend 1k+ on a system that look better, but is NOT AS EFFICIENT in freeing up power, and does not equal the flow of a cooling system that utilizes a radial fan...that what you get with a 911 system, plus one hell of alot of expense when a part goes bad.

Alex April 21st 2003 22:44

My 2 cents:

From the AC Technology website:

Power losses: Fans take power to drive.Some companies claim that up to 17-20 HP can be lost from driving the 911 fan, but we have found that on the Type IV engine, driven at 1.3:1, that this is far from true. The fact is that maybe the sources of these statements do not desire to build an engine that is custom and takes more time, regardless we have found that it is far from true, at least on a Type IV engine. The Type IV engine has a lot more cooling surface that the TI engine does (23% more surface area). I feel that when a 911 fan is used on a Type I big HP losses could occur as the fan must work HARDER to move the greater volume of air past more restrictive cooling fins, plus there are less of them, the end result is a fan that cannot move more air than it can expell, and therefore it backs up in the shroud/fan and pulls more HP from the engine.With the more surface area of the Type IV engine the air is not congested as severely, and is expelled faster, this alone is one reason why the fan does NOT pull as much HP from a Type IV engine as some may have found in testing with Type I engines. As a general figure I have found a 911 fan assembly on a Type IV engine has pulled 8-11 HP from the engine on the dyno in back to back test at the same engine temperatures. The radial fan of the Type I engine normally pulls 9-14 HP from a Type I engine. Basically the larger fan does use more power, but not that much. The condition of the battery and charging system does have impact as well, this is just what I have found in my testing.

Again....something does not add up here. So they are good but they are not?

If you get different results with different shrouds you should not generalize your findings.
Also you can buy a Porsche shroud and put it in your bug for 600$ (Fat shroud with used Porsche fan/ alternator). That is nearly the same amount as the original DTM and maybe less than your shroud. You can get them for about 700-800$ in Germany. The radial T1 fan is known to fail (explode).
More damages will be done if it does. This information can be found on Shoptalk or . Even you had fans go bad.

I really want to know why you generalize the Porsche shroud thing. If you said that you tested most of the shroud designs out there....with the different fans and their sizes I would be quite.

If one or several shrouds are bad so be it. If you say that they are all bad then I and I guess the others would like to know which ones you tested.


Massive Type IV April 21st 2003 22:51

Alex, That information is about 2 years old, and probably needs to be deleted altogether, as it has been superceded.

I will save what I think until my new site is revealed for my shroud. Almost 75% of my test work with other systems on the same size engine is finished.

You know alot of european Tuners. If you would like to see this finalized have them each send me a shroud and I'll test it against the others, and against mine for overall effectiveness, power drain, and temperatures at 4 different RPM ranges.This is not a Joke, if you want the truth to come out this is the time to do it.

Alex April 21st 2003 23:11

I would love to see that but you do not understand one very crucial thing:

I am not saying all this because I doubt the DTM or your shroud.
I have very high respect on what Joe did and you are doing right now. I think the DTM and new shroud are very effective cooling systems and it is better for the entire market to have mutiple solutions available to them.

This is more about you generalizing the 911 shroud debate which no one really can until we have this huge test I guess.
I can also say that the German tuners will most likely not sent you a 911 kit for testing. They do their own testing. As you know me....I have no problem in saying that a particular shroud is not good, ones test show it.

But here is something I can do.......I will write that 911 shroud article and if you want you can give me all the info you have on what worked and what did not for you. I am going to Germany on the 21st of May and I will meet quite a few tuners to get infos from them for the site and I will also try to get as much infos as possible on their 911 kits. I am trying to get a video camera to take and I know Rolf Klaus has a chassis dyno so maybe I can get some informations from him. I will try to get all the right information, tests and even prices and I will put it on the website and it will only cover the 911 kits since it is the focal point of this debate.


please believe me when I say that this has nothing to do with your shroud or the DTM. I do not want to try to make the 911 shroud stand out but I refuse to believe that all the 911 kits are bad, not effective and are just for looks. The cost is not that much higher.If you are willing to provide me your information we can get this solved once and for all. The information on your website had to come from some tests or findings you made in the past.



Massive Type IV April 21st 2003 23:30

I would be more than happy to send them one of my shrouds for test work, because I know the results......

There wil be atleast 4 direct comparisons with other shrouds on my site, but of course I cannot name the companies that the other come from. I plan on being very direct, very point blank and very honest with my results, people will not be happy, and there will be debates, do I care?

That why I will waste no more time with this here, i would rather save the details for my site, which will be up and going within about 2 months

The big difference is that I promote practicality and efficiency among everything else, this is not the general way to market a product, and I'm no marketer anyway.

In my writings you may see me refer to a certain system as a dumb blonde, because thats what I have seen from it, they think they look good, they are expensive to have and they don't know much else about anything.............

Alex April 21st 2003 23:46

That is fine with me Jake.

The debate is about you providing information at one point and at another time the information is reversed completely. On every board it was said the 911 kits can they do not cool as good as the DTM. It was said that the 911 kit uses less hp on your site and on shoptalk and now they use more.

Where did the information then come in the first place?

Let me try to name the 4 shrouds.......CSP, Sharpbuilt, FAT and Bernie Bergmann or CIP1.

This thread is getting so generic now I moved it to the engine forum.

Massive Type IV April 22nd 2003 00:52

I said that it did not overcool on the dyno, nothing will overcool with ambient temps over 100 degrees almost all the time.

There is no way to tell if it will overcool on the dyno, but you can sure as hell tell which one does a better job of stable cooling in a higher temperature climate.

The overcooling is from my experience with engines have condensated oil, and carbs that constantly cough due to the charge never warming up.

Like I said, no more here, I'll wait till I can post my information on my turf, and when that happens I'll be ready for plenty of questioning, but the results will be so point blank that questions won't be needed.

BTW, I have found one syustem that cools better than a DTM, and only one, and it is neither a DTM/TI based unit or a 911 unit. Its a stockk cooling system and only one of them exists, as it was a prototype that never had the chance to be reproduced, but it works, and it works like mad, but if you don't have stock tin it will not even uses a stock fan..
First person to figure it out gets a free t shirt!

factman April 22nd 2003 02:34

jake, did you say that there is a T1 DTM kit? i never knew that. i am not putting a T1 in a notchback so i dont have to worry about room anynmore and would really want to maximize my cooling so that i can maximize my performace setting. i never saw that kit on your site unless its not there yet. thanks jake. another thing just to add to the commit. if the 911 fan uses more HP's becuase it is pushing too much air then why dont they just run an underdrive crank pulley to slow the fan down which would really help out with HP's. thats all.

Massive Type IV April 22nd 2003 10:57

The drive on 99% of 911 systems is 1.3:1 or less. I sometimes run them at 1:1 with a 3" pulley on the bottom and same on top, it helps nothing.

Tha factory VW used 1.6:1 on a TI engine, thats what my shroud uses also.

There were only a few TI DTMS made.

zen April 22nd 2003 13:06

they still look damn good :D

i am confused. are we talking about which is better or if the 911 is not efficient enough to use? i am OK with not having the absolute best personally. or i would have waited for jake's shroud.

i am not an engineer and haven't done any of my own testing, but i don't doubt for a minute that the T1 style, stock TIV, DTM and the MassIVe shroud are more efficient than the 911 on a VW engine. i think their design is pretty self-evident of that. doesn't mean that the 911 is worthless either though. just means it is not as efficient doesn't it? if i insisted on the best, frankly i wouldn't be dumping all of this money into a VW. it would be in a 911 (which in retrospect maybe would have been a smarter move). but i love me VWs.

and the fan still looks cool. :D

Massive Type IV April 22nd 2003 13:11

Yes, it does look cool, but thats not what its about to me.....

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