REFLECTOR: Crankcase venting

Wed Apr 27 12:20:26 CDT 2011

Hello Scott,

The racers are smarter than we are!  No, we didn't use a PVC valve -- I
guess the high loop has similar effect, and I suppose the PVC valve doesn't
contribute much to back pressure.

We tried to compromise between how far the nipple protrudes into the exhaust
flow -- hoping to get a little draw -- and how much back pressure it might
add to the turbo exhaust.  Obviously this approach also eliminates oil
streaks on the bottom of the cowling.  We're really impressed with the
IO-550N (and happy with our turbo mods).  The IO-550N is such a strong and
smooth running engine.  Our turbo goal was to not bubble the lower cowling,
which we achieved, but it added two years to the build time!  Having all the
turbo stuff 'scrunched' up tightly below the engine didn't seem to
appreciably add to the engine cooling issues either.  We're still working on
balancing the CHTs better, though.

Bob

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Wednesday, April 27, 2011 12:25 PM
To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Crankcase venting

Bob,

this is exactly what I want to do! 

If the nipple protrudes into the exhaust stream and is cut of parallel to
the flow it will pull the crankcase vapors out, and supposedly increase HP
and clean up the engine by causing the scraper ring to seat harder. At least
thats what the auto racers say.

I'd just like to stop the oil seeps and  keep the blow oil off the cowl!

Nice looking engine!

Scott

-------- Original Message --------
Subject: Re: REFLECTOR: Crankcase venting
From: Bob Jackson (Jax Tech)  <mailto:bobj at jaxtechllc.com>
<bobj at jaxtechllc.com>
To: 'Velocity Aircraft Owners and Builders list'
<mailto:reflector at tvbf.org> <reflector at tvbf.org>
Date: 04/27/2011 09:55 AM

Scott,

I like your first idea -- vent the oil breather line directly into the
exhaust.  When Scott Swing looked our plane over before the first flight, he
told us to be sure to route the oil breather line up as high in the cowling
as possible, which acts as a poor man's oil-air separator.  

You can see our blue breather hose looping all the way to the top of the
firewall in the photo above.  In the second photo, you can see the blue
breather hose attaching to an angled tube nipple that we welded into the
right turbo's exhaust tailpipe.  I believe our hose ID is 3/4", but can't
remember for sure.  

We've got 400 hours on it so far -- a IO-550N that we custom turbocharged,
and we use about a quart of oil every 4 or 5 hours.  I don't think the oil
saved and returned with a separator is all that much and also may be of
questionable value, so just venting everything overboard may be the best
option, and also with less backpressure.

Bob Jackson

N2XF

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Wednesday, April 27, 2011 11:26 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Crankcase venting

John,

I'm taking the Andair out of the breather line today/tomorrow.

I fairly certain the hose is 5/8, but there is a joint in the line where 

it steps down to 1/2" for about 3 inches.

I will replace with 3/4 also and see if that helps.  The Lyc's don't 

tend to have as much blow by as the Cont's, so if 5/8 is min for a 540, 

its certainly to small for a 520!

thanks,

Scott

-------- Original Message --------

Subject: Re: REFLECTOR: Crankcase venting

From: John Tvedte  <mailto:johnt at comp-sol.com> <johnt at comp-sol.com>

To: Velocity Aircraft Owners and Builders list  <mailto:reflector at tvbf.org>
<reflector at tvbf.org>

Date: 04/27/2011 09:15 AM

> Scott,

> 

> Have you tried without the Andair?  What is the size of the crankcase
breather outlet on your IO-520?  Bart @ Aerosport said (for my IO-540K) that
5/8" was the min. (fine for a healthy engine) - and that 3/4" would be fine
in general.

> 

> John

> 

> -----Original Message-----

> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick

> 

> I'm experiencing oil seeps that I think I the result of excessive
crankcase pressure.

> 

> Continentals are notorious for blowby, even when new and require a very
open vent. I installed a Andair air/oil separator which does work really
well in captureing the oil but I fear it is causing the excessive back
pressure.  Anybody else have experience in this regard?

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Aesop

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