[Diy_efi] Venturi effect crankcase breather

[arnie]

> Unless you are running an open exhaust it is quite possible that 
> you will end up pressurizing the crankcase due to exhaust 
> backpressure.  

Open exhaust or not, one wouldn't install such a system without the
precaution of one way check valves.  That is true of the several 
vacuum generating systems employed on an engine.  The pcv system 
is a good example.

> 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.....

Well, I STILL believe it.

GAS

----- Original Message ----- 
From: "Joe Lutz" <joeelutz at hotmail.com>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, July 09, 2003 12:04 AM
Subject: Re: [Diy_efi] Venturi effect crankcase breather


> 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.  
> Joe



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