[Diy_efi] Venturi effect crankcase breather

Wed Jul 9 04:45:16 GMT 2003

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In a message dated 7/9/2003 12:12:17 AM Eastern Daylight Time, 
espresso_doppio at yahoo.com writes:

> How is it easier for oil to foam when the air mixed
> with the oil is being "sucked out" by lower pressure
> in the crankcase?
> 

aeration doesnt occure form air being in the crankcase. aeration occure when 
the oil basically becomes low in viscosity and begins to have a low enough 
surface tension to contain a gas and become a bubble. lowering the pressure will 
only egxacerbate this problem. if you do go this route go up in oil viscosity. 
its not gonna be a perfect vacum and there will also be exhuast gass's there 
to propigate the problem. the gas sweeps by the oil film and it blows bubbles 
havent you played with any kids bubble makers lately ? 

 as for reducing the boiling point of the oil this could very well cuase the 
airation your trying to stop by creating vapor. yet again going with a heavier 
viscosity index oil and a high Temp rating at a specific viscosity will help. 
all fluids increase in boiling point at pressure goes up. as pressure goes 
down so does the boiling point. for instacne Water will boil at room tempature 
at 30inches of mecrucy vacum. 

  as for the effectivness of such setups. yes the additional ring seal is 
nice. but opening teh second gap seems to really help the problem alot more. the 
thing you are trying to releave is the boundry layer gases that bascially 
cuase ring fluter at high rpm. allowing a larger secondary ring gap will cuase 
these gases to escape. 

 If you do use a vacum pump coupling that with the larger secondary ring gap 
oil consumption may become an issue. remeber the oil is operating at 180F in 
most engines if not morre. the boiling point of conventional 5w30 i belive is 
right around 320 degrees. if you reduce to a vacum then its very possiable that 
at 1-2 inches of water you could be boiling the oil. i havent had a chance to 
verify this but a this film of oil will definately evaporate first. there 
alot of splash oiling going on and this could definately happer it. 

 just my thoughts 

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<HTML>In a message dated 7/9/20=
03 12:12:17 AM Eastern Daylight Time, espresso_doppio at yahoo.com writes: 
 
 
<BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT=
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">How is it easier for oil to foa=
m when the air mixed 
with the oil is being "sucked out" by lower pressure 
in the crankcase? 
</BLOCKQUOTE> 
 
aeration doesnt occure form air being in the crankcase. aeration occure when=
 the oil basically becomes low in viscosity and begins to have a low enough=20=
surface tension to contain a gas and become a bubble. lowering the pressure=20=
will only egxacerbate this problem. if you do go this route go up in oil vis=
cosity. its not gonna be a perfect vacum and there will also be exhuast gass=
's there to propigate the problem. the gas sweeps by the oil film and it blo=
ws bubbles havent you played with any kids bubble makers lately ? 
 
 as for reducing the boiling point of the oil this could very well cuase the=
 airation your trying to stop by creating vapor. yet again going with a heav=
ier viscosity index oil and a high Temp rating at a specific viscosity will=20=
help. all fluids increase in boiling point at pressure goes up. as pressure=20=
goes down so does the boiling point. for instacne Water will boil at room te=
mpature at 30inches of mecrucy vacum. 
 
 
&nbsp; as for the effectivness of such setups. yes the additional ring seal=20=
is nice. but opening teh second gap seems to really help the problem alot mo=
re. the thing you are trying to releave is the boundry layer gases that basc=
ially cuase ring fluter at high rpm. allowing a larger secondary ring gap wi=
ll cuase these gases to escape. 
 
 If you do use a vacum pump coupling that with the larger secondary ring gap=
 oil consumption may become an issue. remeber the oil is operating at 180F i=
n most engines if not morre. the boiling point of conventional 5w30 i belive=
 is right around 320 degrees. if you reduce to a vacum then its very possiab=
le that at 1-2 inches of water you could be boiling the oil. i havent had a=20=
chance to verify this but a this film of oil will definately evaporate first=
. there alot of splash oiling going on and this could definately happer it.=20=
 
 
 just my thoughts 
 
 </HTML>

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