Safe Fuel Pressure

[broebkelange]

whats the max fuel pressure you would use? is it okay to put 170psi on the rails? i got a fuel pump for free that has that high rating and was just thinking of putting it in [img]/ubbthreads/images/graemlins/tongue.gif[/img] .

[Paul H]

One thing to remember,
1 the fuel fitler housing will not hold pressure of that much.

2. anything over 85 psi is a waste due to high fuel pressure can make the injectors hard for the intensifier piston to push down and fire.

The injector wants to see 72 to 80 psi. The bigger the difference in the injection oil pressure and the fuel pressure the easier it is for the injector to work. The only reason to up the fuel pressure is to insure the injector re-fills with a new load of fuel as quick as possible.

[broebkelange]

i was thinking of a dead end system without fuel filter housing. i have an inline filter already (fuel filters for psd in germany $100+). the other consideration was the higher the fuel pressure, the higher the injection pressure would lead to better atomisation and better burn up in the cylinder. as far as i understand the injector acts as an multiplier, large piston to small piston. so if you rise one of the pressures, oil or fuel, you get a better injection. hope my english is readable [img]/ubbthreads/images/graemlins/crazy.gif[/img]

[swh22]

Raising fuel pressure won't increase your injection pressure, only your oil pressure and the ratio are going to change it.

F1/A1 = F2/A2

That's your simple hydraulic type equation

F1 = oil pressure
A1 = fixed (7.11xA2 in these injectors)
A2 = fixed
F2 = the final fuel injection pressure

The fuel supply pressure has nothing to do with it, as long as there is enough to fill up the cavity in the allowed time. It's a little counter-intuitive at first.

Also, dead end systems have trouble getting air out, which may or may not be an issue in our trucks. The super-duties use split-shot injectors and dead-end rails, but those injectors tend to bring some air out of the fuel and then it has nowhere to go. It might not be a big issue with these single shots. A bunch of people have used a pressure regulator after the rails and then just a return back to the tank. Works great and you can adjust pressure to what you want.

Good luck!

Steve

[BIGBEAN]

Performance will come down with anything over 70psi. Single shots like to run at right around 60psi. The mechanical pumps in the OBS seem to run better when the pressure is up a little but I think this is do to to it being set at an idle and once you get on it there is a pressure drop so 75psi at an idle may translate into 65psi at wot. The electric pump set to 60psi will feed the injetcors all day long with all teh fuel they want.