REFLECTOR: Breather tube

[John Dibble]

I thought PCV did create a little crankcase pressure.  My 1975 BMW 
motorcycle had that feature and they forgot to redesign the main seals 
for the higher pressure and I had problems with leaks.  I solved the 
problem by removing the PCV device and just venting to the air.  As was 
mentioned, the main thing is to have adequate ventilation to avoid 
engine oil leaks.  As your compression leak increases with age, more 
venting will be needed.

John

On 3/2/2012 11:54 AM, Grover McNair wrote:
>
> Positive crankcase ventilation, that is applying vacuum, has been 
> shown to increase horsepower marginally. This came about in the late 
> 60's when pcv systems were first used on cars to reduce emissions. I 
> agree with Scott, The last thing you would want to do would be to 
> pressurize the crankcase by pointing the tube forward. Negative 
> pressure is best.
>
> Grover McNair
>
> *From: * reflector-bounces at tvbf.org 
> [mailto:reflector-bounces at tvbf.org] *On Behalf Of *Ruben Creus
> *Sent:* Friday, March 02, 2012 11:55 AM
> *To:* 'Velocity Aircraft Owners and Builders list'
> *Subject:* REFLECTOR: Breather tube
>
> I had to temporarily remove the breather tube the other day to work on 
> some wiring stuff. When I place the tube back in place and looking at 
> it,  I thought that as the tip of the breather tube that exits the 
> cowling is cut in a 45 degree angle, then I assumed that if I place it 
> facing the nose I guess it would have air pressure pushing into the 
> tube. If I place it facing the tail, then the air around the tube it 
> might create low pressure and therefore pushing the air out of the 
> tube creating suction. If I place it facing the wing, the air would 
> just travel passing the tube with no effect.
>
> I guess all this rational also depends on the air pressure inside the 
> breather tube coming from the engine, so I did several tests, facing 
> the tube in this three positions and flying a bit. My tests concluded 
> that when the tube is facing the tail It seems I have more oil coming 
> from it as the cowling seems more oily , but is was hard to conclude 
> as the oil leaving the tube could end up how knows where. And where 
> the tube is facing can also impact where the oil will eventually go. 
> Showing all my test were kind of inconclusive.
>
> So, guess the main question is that if you know what is the proper 
> positioning of the 45 degree opening, nose, side, or tail, or if it 
> really matters?
>
> *Ruben G. Creus *
>
> Ë +1.571.215.0025
>
> * ruben at vainneg.com <mailto:ruben at vainneg.com>
>
>
>
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