Fuel Pressure
 

How much full pressure is needed to open an injector that is designed to operate about 38 lbs? When I was talking to Bob last night and he was explaining to me that you needed to lean the engine. He was showing me this display on his dash and plugged into the computer port. The reason I am asking is because if it only takes 20 PSI to open the injector then you could install an in line fuel pressure regulator and unplug the vacuum line so the factory regulator will be wide open. He was explaining about trying to change the computers program but I told him why don't you slow down the gas. That is the one thing that is still mechanical to a point.
Have you tried this?
Dave

fuel injectors are opened electrically the fuel pressure is used to create a proper spray that atomizes the fuel with the air correctly. reducing the fuel pressure will result in a poor mix of gas and air miss fires and possibly burned pistons (worst case) due to puddling. What would be the best method of reducing the amount of fuel injected is to reduce the time the injector is open. there are several ways to do this but the easiest is press the gas pedal less hard :) a second way is to make the computer think it's ingesting hot air either by tricking the IAT or actually ingesting hot air. lowering fuel pressure will only make the spray pattern look more like a sputter than a spray.

Working in this direction, it would be better to RAISE the fuel pressure, for the atomization that Philip1 is referring to. However, you would need to be able to adjust the computer code to reduce the pulse length (length of time the injector is open, squirting fuel) and you would need an adjustable fuel pressure regulator to raise the fuel pressure.
The combination of these 2 for a higher pressure injection would yield roughly the same amount of fuel injected, but better atomized, which would yield a more efficient and complete combustion burn, which leads to less throttle needed to move the vehicle, and better MPG.

Phil,
I understand why you can't just reduce the fuel pressure. What I was referring to making the engine leaner for the H2 that you are making can take over and run the engine.

depends on the engine. but in a FI situation, it won't help you because the o2 sensor will read that you're running lean and it'll lengthen the injector pulse to accomodate lower pressure. if your car is new enough, it may even have a pressure sensor on the rail to tell the ECU what the pressure is... again causing the ECU to try to correct it.

If you want to lean out the engine, just do it like everyone else... EFIE, O2 spacer, or something like that

38 psi?
 

:rolleyes:
Sorry about the rolling eyes, but I'm more accustomed to 3800 psi fuel pressure in my mid-90's era diesel than 38 psi.
Higher pressures provide finer, more uniform, near to atomization of the fuel droplets for more complete combustion, lower emissions and more power.
And now my new-to-me 2005 diesel has injectors that operate at up to 30,000 psi.:eek: Time to bone up on that system.

with gasoline the injectors are designed to run at a specific pressure. You can raise the pressure and the injector will act like a larger injector. Go too far and the pressure will lock the injector either open or closed depending on make and design. I would go with Kamesama's suggestions.