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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.....

vujade April 22nd 2003 13:17

Jake, if they are not that efficient, why do you run a 911 fan & shroud on your Type 1 motor in the plague?

Massive Type IV April 22nd 2003 15:23

3 reasons.

I had the shroud left over from another job the shop....

My engine makes peak HP at 8,500 RPM, I shift at 8K. The 911 fan is much better for taking revs compred to the TI fan, I will agree with that.

the 3rd reason is the fact that the stock TI system is more complicated at the track. with the sharpbuilt system I remove 4 bolts and 3 wires and the entire shroud is removed in 3 minutes, making the engine capable of being removed in 10 minutes when I grenade something, which does/has happened.

I cut 3 large holes on the back side of my shroud, to let air pass through with less restriction.

The biggest reason is that I could not find a TI DTM,, and Joe would not make one for me because they were too much work.

with 12:1 I have no overcooling issues, and with 220BHP you don't drive it on a cold or wet road unless you want to end up in the ditch.

hot66 April 22nd 2003 16:30

just to jump in on this one :)

Jake, did you find cutting the extra holes in the shroud made much of a differenceon your type1 motor?

Massive Type IV April 22nd 2003 16:46

I never did any back to back test on it. When you rev the engine and there is enough back pressure to almost blow the shroud off the engine, you can pretty much tell something is wrong.

Farmer April 22nd 2003 18:12


Originally posted by Alex
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.

I know that Joe Lociero tried to work out a "ratio" thing for the stock shrouded T4s & 914, where he used a "spinner" or something like that to make the fan rev at about 1,4 instead of straight 1. Might that be it ???

(At the time I coulcnt relly follow him, as I/we did not have these problems most likely due to less ambient temps around here. So I never kept track of if he ever got it working.)

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