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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 Cal-look.com . 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.
Alex
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