This is what you need to read. Jake spent some serious time and money gathering this data. You do what you want with it. My shroud has the 1.5" hole in the freeze plug.
From The Samba
Posted: Fri Jan 27, 2006 8:12 am Post subject:
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The line up is as folows
DTM
Stock non modified (includes 181 in my testing)
36HP aftermarket
911 style shrouds
center mounted systems that utilize the stock radial fan (these are HORRIBLE)
VW Gol
Nothing performed as bad as the Gol shroud!
I saw no differences in cooling with the 181 shroud that would prove it's worth the money.
My DTM only beat the stock shroud by about 10% in average engine temperature, but it did significantly decrease temperature delta between all 4 cylinders. The biggest benefit of the DTM was the cooler oil temperatures due to the TIV cooler and the 17% of added airflow we direct through it over stock.
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Jake Raby
www.aircooledtechnology.com Posted: Fri Jan 27, 2006 3:45 pm Post subject:
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Yes, the air was to be metered by the heater boxes and the shroud was designed with this amount of bleed and back pressure in mind. I found that a freeze plug with a 1.5" hole in the center provided effectively about the same results as with heaterboxes installed, pressure wise within the shroud....
Remember that even when the heat is off, the air escapes from the heaterboxes through the tiny bleeders on top of them, there is always air escaping from those "snorkels" on the stock shroud, with the original design.
The same rule has applied to the TIV engine with the heater boxes removed- blocking the outlets in the stock shroud certainly has negative results- mine have been open on the Bus for 5 years. Blocking them off quickly elevates temperature differences and really heats up the #1 cylinder...
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Jake Raby
www.aircooledtechnology.com