Some thing on my burner

[Dawie]

The same was also said about the type 1 fan.(Cavitation at high rpm). People who sold "power pulleys" in the seventies claimed it increased cooling at high rpms, and reduced the chance of the fan disintegrating.
Others claim overheating at low rpm's caused by power pulleys.

Late Mexican beetles apparently used a funnel-shaped ring at the input of the cooling fan,to reduce cavitation. Looks the same as what Jake uses on his version2-dtm.(The version that needs an external oilcooler.)

[flatfourfan]

heheehehehe, just make sure that you don't show anything else Armand..........I'm coming through end of the month, we'll talk again.

[eben]

Almost like the Type 4 funnel dawie?

[Dawie]

Actually the type1 fan input cooling ring tapers in all directions, (more like the front opening of a jet engine). Think it is for sale in the US.
Imagine it could be of benefit in split kombi applications,where there is more space behind the fan.

The funnel in the picture looks like the T4 variant version? The sedan version was more angled upwards,where it eventually connected to intakes in the engine lid.

[eben]

This one is from the variant yes. it runs very close to the lip of the fan which means you don't have to worry about where the fanbelt runs.

[Class 11 streeter]

You guys are killing me! So many secrets!!!

The "cavitation" as I understand is not the actual proper word as cavitation applies to a fluid, but it has been used in the ACVW community for so long that it's hard to get away from what has become the "standard". I guess an aerodynamics engineer would know the proper word for when a fan will not flow anymore air past a certain RPM. Stall??

The type 1 shroud inlet "vortex ring" as we call it was installed on the fuel injected engines starting in 1975 or so and fan shrouds with the ring are still fairly easy to find. The shroud improvement was a result of the emissions tune required for aircooled motors at the time which meant hotter running temps while at the same time the beetle got heavier for increased comforts and safety standards. A simpleton like me knows a "performance" motor also has hotter running temps! I have one of these late shrouds laying around in stash, and the ring looks like it would adapt to any doghouse fan shroud with a bit of welding. There is someone reproducing them, a powder coater I think. Yep, here is his ad on Shop Talk: http://www.shoptalkforums.com/viewtopic.php?t=115698




Now, I don't know what Armand and flatfourfan are scheming, but there is speculation in that advert that the type 4 fan acts as it's own "vortex ring", therefore a layman like me would speculate that there is no need for the shrould improvement if the fan is doing the job from the start.

Am I close?

[eben]

If you look at the lip of the type 4 fan it looks quite "vortex ringy" already I suppose

[calooker]

The early 36 Hp engines ran that ring thing, that looks very much like the one in the pics. but the purpose was not to aid flow but to rather prevent the cold air from entering a cold motor. I sopose one could cut one in half and use it to rather promote flow rather than stop it, just an idea.

[sand]

The original inventor of the DTM made a few of those fans .I have one ,never used it but with my huge motor I am going to try it.