[Diy_efi] Venturi effect crankcase breather

[arnie]

----- Original Message ----- 
From: "Adam Wade" <espresso_doppio at yahoo.com>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Sent: Tuesday, July 08, 2003 11:51 PM
Subject: Re: [Diy_efi] Venturi effect crankcase breather


> --- Djfreggens at aol.com wrote:
> 
> > its not gonna be a perfect vacum
> 
> Of course not.  Blow-by always occurs; ring and seal sealing 
> are imprefect; and there will always be evaporable fractions 
> in the crankcase that will vaporize at low pressures, thus raising
> pressure, or at least slowing pressure drop.  As I'd already noted,
> more than a fairly small drop in pressure will cause damage to 
> rings, cylinder walls, and of course ring sealing.

More than a fairly small drop in pressure..., how small of a drop in
pressure? 

> > as for the effectivness of such setups. yes the additional ring 
> > seal is nice. but opening the second gap seems to really help 
> > the problem alot more.
> 
> Do you mean using a second ring with a wider gap in it?  That 
> doesn't make much sense to me.  You just defeated the purpose 
> of having the ring there in the first place.

Being closer related to the motorcycle industry, I reason that you
would be more familiar with this.  Though it is referred to as a 
'compression' ring, it's main function is to control oil.  A one
compression ring (along with conventional oil ring) has been used
successfully for many years (decades ?) especially in the motorcycle
camp.  

OEM (as well as aftermarket) has been prescribing (and using) 
larger gapped second rings for a decade that I am aware of.  This 
aids in the compression sealing of the top ring, by preventing
pressure buildup below top compression ring.     
 
> > the thing you are trying to releave is the boundry
> > layer gases that bascially cuase ring fluter at high
> > rpm.
> 
> And here I thought it was because of the resonant
> frequency of the ring.  Silly me.



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