@DannyP posted:Stan, and anyone else that wants to "dive off this cliff" with EFI:
http://performancefuelsystems....rface-TechCorner.htm
LOTS of good learning out there to be had.
Thanks for that, Danny. As soon as I started reading, the light went on over my head. I've always been confused why injector pressure needed to vary at all, and wondered even more why vacuum was used to do it. Vacuum seems so... uncivilized for EFI.
As the article says (in so many words), the idea is to maintain a constant pressure in the fuel rail relative to what is occurring in the manifold. If the manifold is under a lot of vacuum, the regulator needs to supply less pressure to keep a constant relative fuel rail pressure. Atmospheric pressure is 14.7 psi absolute (absolute being a perfect 30" vacuum), therefore 2" vacuum roughly equals -1 psi (atmospheric). If the manifold vacuum is 10", then the regulator needs to back off the pressure about 5 psi in order to supply the same relative pressure to the fuel rail.
Brilliant and elegant. I learned something new today. Thanks, @DannyP.