View Full Version : fuel pressure adjustment

06-25-2006, 04:01 AM
I need to know how much fuel pressure can be maxed out on the stock injectors. Right now fuel pressure is at 40lbs. at idle. I need to know is that safe at idle because I am wanting to learn more about these cars because my father own's one. And I would like to gain info about how much i can run on fuel pressure at idle on stock injectors on converted ls1 maf turbo intake system. Hel p me out thanks.

06-25-2006, 11:34 AM
Fuel pressure is a function of manifold vacuum/boost, since it is referenced (via the vacuum tube to the top of regulator). The idea is maintain a constant DIFFERENTIAL pressure across the injector regardless of vacuum or boost.

To get an accurate base measurement (with the compensation), unhook the vacuum line ... that is your "static" fuel pressure. This pressure is what counts, since it is what the injector "sees" during it's range of operation.

Stock injectors can take upwards of 55 psi STATIC pressure, but start exhibiting erratic spray patterns and delivery towards the top of that range at higher duty cycles.

As an aside, if the car is in closed loop at idle, it will compensate fuel delivery (longer or short pulse widths ... indicated by the Integrator and BLM) for what it is seeing regardless of fuel pressure. If you screw around too much with the pressure, you'll see the BLMs peg one way or the other and then you will start seeing rich or lean conditions.

Basically, just cranking fuel pressure based on idle readings is pretty much a waste of time.