Fuel pressure regulators, was Re: Fuel pump questions

[Christopher Bruno]

Ed wrote:
> 
> OK people, time for me to start a new fuel-related thread. This time
> it's regarding the fuel pressure regulator.
>         Just about all OEM EFI setups I've looked at have the FPR mounted
> directly to the fuel rail. Would it make much of a difference mounting
> it remotely? I was installing nitrous on a 94 Supra that had a custom
> fuel system made up of a Paxton fuel pump, filter, and regulator (and
> massive 10AN lines). The FPR was mounted before the fuel rail, not on
> it. Is this acceptable or should it have been plumbed onto the rail?
> 
> -Ed
It doesn't need to be plumbed onto the rail necessarily but it does
have to be AFTER the rail.  The way a fuel pressure regulator works
is it is essentially a controlled way of blocking fuel flow.  Think
of pinching the the fuel line and letting only a little fuel through.
This is how a pressure regulator works.  The reason to have it close
to the fuel rail is so that the pressure at the regulator more closely
represents the pressure at the injectors.  For example, if you were
to plumb the pressure regulator all the way back at the tank (on the
return line), the pressure at the injectors would be much higher 
because of head loss through the return line.  

Hope this helps.
-- 
Christopher Bruno
Teradyne
321 Harrison Ave. MS/H63
Boston, MA 02118
617.422.2040 Office
617.422.2304 Fax
bruno at icd.teradyne.com