12SecZ

Yes.

dr_gallup

The relationship between injector flow and fuel pressure is a little more complex than most poeple realize.

First, electronic fuel injectors are "simple" on/off solenoid valves. While the injector is open the flow rate is proportional to the square root of the pressure drop across it. So doubling the pressure will only increase the flow 41%.

Second, increasing the pressure will increase the time it takes the injector to open and decrease the time it takes to close. Typical injector opening times are on the order of 1.5 milliseconds and closing times about 0.5 milliseconds. So at a typical idle pulse width of 2.5 milliseconds the injector is open and flowing for around 1.5 milliseconds. So the time that the valve is open, for a given pulse length from the ECU, will decrease as pressure goes up. If you increase the pressure enough the injector will not open at all. The effect of pressure on response times varies widely with the design of the magnetic circuit and the valve geomerty.

Some injectors, notably the GM Multec I, will actually decrease flow at 2.5 ms when you increase fuel pressure from 3 bar to 5 bar. However, the flow does go up at longer pulsewidths. The injectors that RC Enginering sells are particularly good at working to higher pressures and at shorter pulswidths, two important factors for turbo applications.

One last thing, the fuel pressure will in no way affect the life of the injector.

Loren04G35

I had an interesting discussion with Jim Wolf about this. The old return fuel systems used a 3 bar fuel system where the base fuel pressure is equivelent to 3-bars of pressure or 14.7 psi x 3 = 44 psi. For the older Nissans, they woudl run 43 psi without the vacuum to the fuel pressure regulator. The new fuel system uses a variable flow fuel pump to control the pressure from the tank. Back in 2000, Ford said their variable pump ECU for the 2000 Mustang was more sophisticated that the Engine ECU. The new fuel systems are designed to run more pressure from the factory. The Z/G pump is a 3.5 bar, 52 psi system. For ATI, they are using a different variable fuel pump to ramp up the pressure more. Believe it or not, the new system only runs a couple psi higher pressure over the stock system.

This is actually a big improvement over the old FMUs that were used on return line systems. The major advantage is that it keeps the flow of the pump up with the fuel pressure. With the older systems, as the FMU increased the fuel pressure; the fuel pump would actually flow less fuel as the pressure rises. A bigger pump or a secondary in-line pump was necessary to stabilize the pressure. The new pump system is just a lot simpler. JWT is considering using this setup for their own turbo kit they are developing.

On the idle pulse width, the typical is actually less than dr_gallup posted. Once into closed loop, most systems run 1.8-2.0 ms. When revving and letting off, you may see 2.7 ms, but the ECU will keep dropping the duty cycle until the O2 sensor is continuously changing modes from lean to rich. My own custom ECU program with 555cc injectors in my Maxima is set to idle at 2.0ms. As the ECU has gone through learning, due to the big cams it is now at 2.2 ms; but the default was 2.0 ms.

12SecZ

So to reiterate the short answer is yes.

zland

All the guys that know more than me and posted on this thread:

My concern was durability of stock injectors and that engine is running properly, ie not too lean. Am i processing this data you guys posted in that ATI's solution is ok by boosting pressure and using stock injectors?

thanks to all. Jeff

jesseenglish

Yes, it is a proven method that has been working in thousands for cars for many years. It is crude, but when tuned properly it is very reliable.