So, lets say typical fuel pressure is around 45psi, at idle. Has anyone seen fuel pressure readings across the rpm band, at varying throttle conditions?
I'm curious to see what a typical stock pump can output.

Also, does the ECU control injectors to vary spray under these same conditions?

I know this seems to be a fairly basic question, but i think im going somewhere with this, i think..

 

Stock fuel pump out put with what injectors? The bigger the injectors the more fuel you need to flow to maintain the same pressure.

 

Don't know the exact numbers, but a stock fuel pump can put out more than 45 psi. The fuel pressure requlator (in the fuel rail) keeps it at 45 psi.

The ECU varies the injector pulse width (open time to closed time) with engine load, so the injectors stay open longer when you need the extra "oomph." Spray pattern stays the same.

The pressure is relatively constant through the rpm range.

 

ok, regarding spray, i understand, its simply a function of duration. fair enough.

now, regarding the pump, i know that the fpr (stock or aftermarket) keeps it at a set pressure, at idle, BUT, does it change based on rpm and/or load?
i would imagine yes. if you think about it, youd be running awefully rich and burning a lot of gas if you were running the same pressure at 800 rpm as 8000rpm. by the same token, there may be chance for detonation with Xpsi at 8000rpm...

anyone else?
thanks

 

I have a 99 si with an autometer fuel pressure gauge on the hood. Your fuel pressure will vary depending on vacuum in the intake manifold. At idle i pull about 20 in./hg. and my cars runs right at 39-40 psi. At WOT it goes to 45-47 psi.