REFLECTOR: Oil Breather Nipple Into Exhaust Pipe

[Chuck]

Bob, have you considered an air-oil separator? The turbo's will create higher cylinder pressures (temps) and thus more blow-by through the rings. This will send more oil/water vapor out the breather and into the exhaust/atmosphere. Anytime you weld an exhaust pipe, your adding a stress riser which can crack and fail. If you do it, you might want to have it normalized (heat treated) afterwards.

I've had a separator for years and it works well. I'm also finishing my add-on turbo and plan to keep the same system. I get very little oil through the separator discharge tube and my oil analysis has been fine.

Chuck H



  Bob,

  A simpler though less aesthetic solution would be to clamp a short length of pipe to the leeward side of the current exhaust pipe and exiting the cowl through the same opening that you have currently. You could attach the oil breather tube to this pipe. If the exit end of the pipe is cut diagonally  as your exhaust pipe may be, I believe that will give the slight negative pressure that you are looking for. This solution also may mitigate the freezing over of the breather line.


  Kirk


  > From: bobj at computer.org
  > To: reflector at tvbf.org
  > Date: Tue, 22 Apr 2008 22:04:35 -0500
  > CC: bobj at JaxTechLLC.com
  > Subject: REFLECTOR: Oil Breather Nipple Into Exhaust Pipe
  > 
  > Does anyone have experience or ideas for the best way to weld a nipple into
  > the exhaust pipe for the oil breather hose?
  > 
  > We want to weld a nipple for our oil breather hose into the short exhaust
  > outlet pipe of one of the turbochargers (we've custom-added to our IO-550N).
  > We are aware of several issues and concerns. One issue is how far the
  > nipple is extended and/or is angled into the exhaust gas stream. If for
  > example on the inside of the pipe, the nipple is extended and angled away
  > from the turbocharger, it might create a small Venturi effect and help draw
  > moisture and oil 'fumes' out of the crankcase. But if angled away too much,
  > this Venturi might be strong enough to excessively de-pressurize the
  > crankcase and cause problems.
  > 
  > Or, if the nipple were angled a little too much back into the direction of
  > the turbo exhaust, it could positively pressurize the crankcase and cause
  > engine seal problems.
  > 
  > Hopefully, there is an angle of the nipple that creates no positive
  > crankcase pressure, and with just the proper, small amount of negative
  > pressure to help draw out the oil fumes slightly.
  > 
  > Another issue we're concerned about is that this short stub of a breather
  > nipple on the inside of the turbo exhaust pipe could eventually burn through
  > or break off and strike the prop. This has apparently happened in the past
  > with some certified aircraft (not bang into the prop, just break off).
  > 
  > Finally, we've also heard that if the nipple enters the exhaust pipe at
  > right angles and is flush cut with the wall of the exhaust pipe, not
  > extending into the inside of the breather nipple, it may be slightly
  > pressurized and can become completely clogged with 'soot' over a period of
  > time.
  > 
  > If anyone has experience or suggestions for how far in to extend the oil
  > breather nipple into the exhaust pipe, and which way to angle it, we would
  > appreciate the help.
  > 
  > Or alternatively, if someone has a (TCM or Lycoming) engine with a factory
  > installed oil breather nipple, maybe they could look to see how far the
  > nipple extends into the exhaust pipe, and at what angle.
  > 
  > Thanks,
  > Bob Jackson
  > N2XF -- Ten years and still working!
  > 
  > 
  > 
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