Dual fuel PFI rails....

[Shannen Durphey]

Barry Tisdale wrote:
> 
> Something got lost in translation here, I think.  (BTW, was using my wife's account for the original message - I'm back home again).
> 
> DUAL fuel; I'd need *two* parallel holes drilled the length of the bar.  Cross-drilling the two longitidinal holes where the injectors will be placed, plugging the access opening to the outside of the rail.  This results in two parallel holes, connected by cross-holes where the injectors will go.  Drill the injector feeds into this hole, between the long parallel holes, so's one injector can be fed by either of the two 'logs'.  One log would carry pump gas, the other, the fuel of your choice, probably avgas.  Two separate circuits, tanks, pumps, regualtors, etc. It would take about 0.2 sec for the fuel transition to occur; the volume of 'old' fuel to be flushed out of the common volume before the injector saw 'new' fuel.
> 
> Only problem is the drilling of two parallel holes in, say, a 1" x 3/4" bar, about 9" long - say, 5/16" holes & cross-drillings.  Is this do-able??
> 
> Assembling out of tubing & welding all the fittings would be tedious, at best, and surely beyond my skills.  If I had the 9" bars drilled, I could probably take it from there.
> 
> Technically, any comments?  Surely, this isn't the first time anyone has thought of this; anybody done something similar?  Probably ideal is a manifold w/ 2 injectors per intake port, but this is *really* beyond my capabilities.
> 
> Sincere thanks for any feedback - Barry

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