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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
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Aircooled engine can be modified to take boost upwards 2 bar but it's inherent problem isn't mechanical integrity but head temperature. At those boost/power levels head cooling fails. Aircooled head cooling has always been marginal, and alloys used in process usually loose their strength above 200 deg. C. This has always been the problem with aircooled design and Porsche themselves finally accepted the defeat and went to watercooled heads when more power and better emissions couldn't be achieved trough existing design. There is just not enough cooling area there for that kind of power. 4-valve design is also impossible to do.

Porsche used different alloy composition for their turbocharged cars for a while but problem is still there. If you want to use 2 bar for more than short bursts, higher fan gearing and head temperature sensor should be used.

If temps climb over 210 deg. C, boost should be lowered.

Even if head will occasionally survive a venture into higher temperatures, it's integrity will change and you might get into all kind of problems later on. Warped heads, loosened head studs, unseated valves etc.
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Old 02-01-2007, 01:53 AM
  Pelican Parts Technical Article Directory    Reply With Quote #66 (permalink)