Dual fuel PFI rails....

[Barry Tisdale]

Hey, thanks for the reply!  What I had in mind is very like what you suggest, with solenoid valves to block the return line of the fuel *not* in use; one NO (normally open), one NC.  Both switched to follow their appropriate pumps; analagous to ORing them.  Reason for the *two* rails is to minize the switchover time; the more volume common to the two fuel circuits, the greater the time to purge the 'old' fuel and the longer the time before the injector sees the 'new' fuel.  I'd like the system to be transparent, switching at, say, 1 psi of boost to the higher octane fuel.  With two rails of 5/16" diameter, 1/4" common bores feeding the injector, switchover time should be 0.3 seconds or better.  Seems to be just a mechanical problem, like what to make the assembly out of & how to fit it into the space available, same mounting setup, etc.

I'll check the archives as you suggested.

Thanks for the advice; certainly appreciate it! - Barry 

At 06:05 AM 6/15/99 -0400, Shannen Durphey wrote:
>You'll want to use something to shut off the fuel system that isn't in
>use, to prevent dilution and the transferring of fuel from one tank to
>the other.  Once you've done this, there's no reason you can't run a
>single rail system.  To reduce the time required to switch fuels, tee
>the lines directly before and after the rails, and install the
>isolation valves there.  To reduce the amount of tubing used, tee the
>lines back at the tank and install the isolation valves there.  Design
>the system so hot soak conditions don't put the injectors under
>extreme pressures and cause leakage.  Look through the archives, Greg
>Hermann has described an ideal fuel rail design.  I'd try to set it up
>so isolation system failure doesn't mean a dead car.  One set of
>valves is normally open, one set is normally closed. 
>Shannen
>
>