[Diy_efi] Venturi effect crankcase breather

[Joe Lutz]

During Overlap, if you have a well designed exhaust, the in cyl pressure can 
drop to around half an atmosphere during overlap and even the first part of 
the intake stroke.  So either you suck in fresh charge from the intake or 
you suck in a mix of fresh charge and a very small amount of mostly inert 
gas from around the rings and side of the piston that may have a very little 
unburned hydrocarbon mixed in.  Power is directly proportional to mass flow 
through an engine, so I want to move as much mass through it as possible.  
Space taken up by inert gas, as little as it may be, is space not being 
taken up by fresh charge full of chemical energy to be extracted by 
combustion, not to mention there would be uneven mixing of the residuals and 
fresh charge hindering combustion even further.  So we loose a minute amount 
of unburned hydrocarbons.  I have yet to see an egr valve on a race engine.  
(there probably is one somewhere)

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 23:49:26 -0700 (PDT)
>
>--- Joe Lutz <joeelutz at hotmail.com> wrote:
>
> > the main reason is because the vacuum helps to
> > evacuate residual mass from the ring lands that
> > would otherwise dilute the fresh charge.
>
>Now correct me if I am wrong here, but wouldn't that
>A) be extremely minimal, considering the amount of
>intake charge compared to residual mass, and B) be
>contained mostly along the boundary layer, thus not
>only not impeding combustion, but actually allowing
>for increased fuel efficiency due to less unburned HC?
>
> > Oops, did I say that out loud?
>
>Don't worry, we won't tell.  ;)
>
>=====
>| 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     |
>
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