[Diy_efi] Donegan ECU

[bearbvd at mindspring.com]

Original Message:
-----------------
From: Steven P. Donegan donegan at donegan.org
Date: Fri, 05 Jan 2007 10:40:53 -0800
To: diy_efi at diy-efi.org
Subject: Re: [Diy_efi] Donegan ECU


 > On Thu, 2007-01-04 at 12:23 -0600, cobraman at insightbb.com wrote:
> > > My "Edelbrick" ProFlow has fuel pressure controlled with 
> > engine vacuum. On track sessions on very hot days, the fuel in 
> > the rails will boil under hard braking - accelerator closed (low 
> > fuel pressure). When you finally step on it (52 psi), nothing 
> > happens until the vapor "recirculates" or is expelled.  
> > Usually takes a second or so.  I don't think dead heading 
> > would do any better - probably just need to keep a constant fuel 
> > pressure. 
> > > IMHO, hot fuel should give better economy - easier to vaporize 
> > - for those green members.  TomS
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > ld
> > > > consume the gas in the rails well before it got warm :-) 
> > However this
> > > > does raise a point - perhaps my ECM/PCM/EFI computer needs a 
> > way 
> > > > to open
> > > > a fuel return line and to sense fuel temp in the rails? Any 
> > > > ideas on how
> > > > useful that would be in the 'real world' anyone?
> > > > 
First-- plumb the rails as with any 'two phase' (gas/liquid) piping system.
Industrial refrigeration piping practice is a good example. Injectors
pointed downward--where you want liquid. Uniform slope to one high point,
so that no vapor is 'trapped' anywhere but at the high point. Finally--put
a fixed size bypass/return orifice--about a .045" Holley jet will do
FINE--at the HIGH point. It's utterly astounding how FAST a LOT of vapor
will go through an orifice that size !!

Greg

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