[Diy_efi] Venturi effect crankcase breather

[Joe Lutz]

I very seriously doubt that you will pull enough vacuum from an exhaust 
venturi to cause boiling problems.  Unless you are running an open exhaust 
it is quite possible that you will end up pressurizing the crankcase due to 
exhaust backpressure.  Only time I've seen this done is in dragsters with 
open collectors.  Now Winston Cup cars pull really strong vacuum in the 
crankcase with the aid of multistage dry sump pumps.   Most people believe 
the reason for most of the Hp gain is from improved ring seal and less 
viscous drag on reciprocating components due to lowered density of the 
crankcase gasses.   These factors do help, but the main reason is because 
the vacuum helps to evacuate residual mass from the ring lands that would 
otherwise dilute the fresh charge.  Oops, did I say that out loud?

Joe


From: Adam Wade <espresso_doppio at yahoo.com>
>Reply-To: List for general do-it-yourself EFI talk <diy_efi at diy-efi.org>
>To: List for general do-it-yourself EFI talk <diy_efi at diy-efi.org>
>Subject: Re: [Diy_efi] Venturi effect crankcase breather
>Date: Tue, 8 Jul 2003 21:11:16 -0700 (PDT)
>
>--- Djfreggens at aol.com wrote:
>
> > if you reduce pressure the boiling and aeration
> > points go down. IE the less pressure there is the
> > easier it is for oil to both foam evaporate and
> > boil.
>
>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?
>
>I don't believe any mention was made about the boiling
>point of the various fractions of the oil, and
>frankly, I would think that faster evaporation of the
>unburned fuel in the oil would be an advantage in
>lubrication, not a disadvantage.
>
>=====
>| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
>| "It was like an emergency ward after a great catastrophe; it  |
>|   didn't matter what race or class the victims belonged to.   |
>|  They were all given the same miracle drug, which was coffee. |
>|   The catastrophe in this case, of course, was that the sun   |
>|     had come up again."                    -Kurt Vonnegut     |
>
>__________________________________
>Do you Yahoo!?
>SBC Yahoo! DSL - Now only $29.95 per month!
>http://sbc.yahoo.com
>
>_______________________________________________
>Diy_efi mailing list
>Diy_efi at diy-efi.org
>http://www.diy-efi.org/mailman/listinfo/diy_efi

_________________________________________________________________
The new MSN 8: smart spam protection and 2 months FREE*  
http://join.msn.com/?page=features/junkmail


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi