High Pressure FI, pros/cons Options

[McMark]

AFAIK, most never fuel injection systems use much higher fuel pressures in their FI. I'd imagine this is to achieve better fuel atomization for fuel economy. Since I have tunable FI I was pondering what it would take to increase the runing fuel pressure and wether it would be worth it.

OBVIOUSLY the fuel supply/return lines should be upgraded to steel for safety.

Would new injectors be necessary? The FP regulator would need to be replaced. What else?

[lapuwali]

Yes, you should get better atomization at higher line pressures.

You'd not need to go to all-steel lines. There's 150psi rated FI hose out there, used no most newer cars. CIS still uses rubber lines in several places, and they run at 100psi. The common pressure used today is basically 3 bar (43.5psi, the usual range being 42-44psi), and the stock system runs at 2.

The stock injectors would probably still work at 3 bar. I know people who've run "modern" EFI to 5 bar using injectors normally run at 3 bar. If you do decide to go with newer injectors, you're also looking at fabricating fuel rails, too, as you aren't going to find 3 bar hose-barb injectors.

One thing a number of modern systems also do is run the fuel pressure referenced to manifold pressure, using a regulator with a vacuum line. This keeps the pressure drop across the injector constant. With the D-Jet system and its fixed fuel pressure, the pressure across the injector is lower at full throttle than at idle, since the manifold pressure is higher at WOT, so atomization is actually worse at WOT than it is at idle. This is somewhat compensated for by higher air velocity at WOT, but it's still hardly ideal. Another advantage of this setup is you can run larger pulsewidths at idle and smaller ones at WOT, giving you better control of mixture. Idle pulsewidths on D-Jet setups are pretty much at the limit of what the injector can physically handle.

You could set this up without going to 3 bar, either. You can just get an adjustable FPR with a vacuum connection, and adjust it down to 2 bar.