simple question about fuel press. regs.

[Clare Snyder]

Bruce Plecan wrote:
> 
> -----Original Message-----
> From: TWright669 <TWright669 at aol.com>
> To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
> Date: Tuesday, March 31, 1998 2:25 AM
> Subject: simple question about fuel press. regs.
> 
> >I am trying to build a basic theoretical fuel map but there is one thing I
> am
> >not all that confident about:  the effects of the fuel pressure regulator.
> >There are two types:
> >1. the constant pressure type, and
> >2. the manifold pressure referenced type.
> >I have the manifold reference type.
> >My question is:
> >Does the manifold referenced regulator inject the same amount of fuel per
> >milisec. over the range of manifold pressures?  After all, for every 1 psi
> >increase in manifold pressure there is 1 psi increase fuel pressure, which
> >cancels out. Right?
> 
> That's been my experience
> 
> >A person who has a constant pressure fuel reg. has to do extra calcs. to
> >figure in the effect of manifold pressure for the rate at which the
> injector
> >injects fuel, where as I dont have to bother.  Right?
> 
> I took a system that had a fixed FPR, and went to vac ref., and it
> was easier to dial in, and much more stable for AFR
> 
> snip
> 
> >Thanks,
> >Tom
> 
> Cheers Bruce
The compensating, or variable, fuel pressure regulator has only one
purpose in life. To make it easier to control fuel delivery over a wide
range of manifold pressures. A properly designed MAP controlled system
"can" get away without this mechanical complication, as it already knows
the manifold pressure and "can" compensate for it. I emphasise "can"
because not all do. A mass air system cannot readily compensate, and
therefore almost requires the compensating regulator.
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