REFLECTOR: Air Filter (was: RAM air and a "cold box" intake), oil analysis

Sid Knox sbjknox at earthlink.net
Sun Jul 9 12:20:17 CDT 2006


> What is your experience with not having an air filter?

I have no quantative data that I consider meaningful.  For a few years I 
sent an oil sample to the lab and sometimes the silicon would be near the 
recommended limit but sometimes not.  The engine (IO-320) and mating Hartzel 
constant-speed prop came from a Texas airplane junk yard (one side of a twin 
Comanche).  The log book indicated about 1600 hours.  It sat for about 25 
years in a guys garage before I got it.  The diaphragms in the Bendix fuel 
servo had turned to stone and it would have cost at least $1300 to fix it 
(including upgrades).  That's when I decided to roll my own.
The engine runs strong, compression in high 70's, burns a quart of oil every 
8 hours, and does not leak oil.

I have quit doing the oil analysis because I was never able to gain any 
useful insight trying to interpret the nearly random-appearing reported 
values of the various contaminants.   When I first cranked it up after its 
25-year siesta, I ran it for a few hours (not flying yet) and drained the 
oil. It (and the filter) was loaded with dirt and carbon but no metal, so I 
went ahead with the EFI.  After about 10 or so hours, the engine had 
cleansed itself and so it remains today.  I do cut open the oil filter each 
time I change it and so far my junk-yard engine is as clean as my relatively 
low-time IO-360 Velocity engine.

Sid Knox
Oklahoma

Velocity    N199RS
Starduster  N666SK
W7QJQ

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