Posted for "Douglas Brunner" <douglasbrunner@earthlink.net>:

 I would like to solicit comments on using Positive Crankcase Vacuum in the
engine of my IO-550 N in a Legacy.
 
 As I understand it (I am not an engineer and don't play one on TV) creating a
vacuum in the crankcase of an engine has a number of beneficial effects:
 
 1)  There is an increase in horsepower related to a decrease in "windage".
 
 As far as I understand it this means that there is decreased air resistance
to the movement of the crank, rods, etc. inside the crankcase and this
translates into decreased "drag" on the moving components of the engine.
 Supposedly, this translates into an improvement of approx 5% in horsepower.
 There is a fair amount of information about this on the Internet with respect
to auto engines and it seems that racing engine run with crankcase vacuum.
 
 2)  There is a reduction in oil consumption and oil leaks.
 
 This is a secondary benefit of the vacuum.  It causes the rings to seat
better and less oil is consumed.  Also since the case is "sucking" rather than
"blowing" oil is much less likely to leak.
 
 Mark Frederick of F1 has used positive crankcase vacuum in his engine and
recommends it highly.  I am looking for comments from others more
knowledgeable than myself about using it.  (I am aware that it violates the
K.I.S.S. principle)
 
 Doug Brunner
 N241DB (reserved)
 douglasbrunner@earthlink.net