sti.dean

can a fuel pressure regulator be to far from the end of the fuel rail?
the reason for asking i have a 3psi dip in differential fuel pressure as boost rises, the fpr is situated on the other side of the inlet manifold which is about 3 feet of pipe from the standard position on the end of the fuel rail. could this cause a pressure drop?
3psi doesnt sound much but it is around a 6% drop
thanks
dean

1509joe

iTrader: (2)

Shouldn't have a drop in pressure MAYBE a very slight delay. I would look at elsewhere for your problem.

sti.dean

hi
Got any sugestions, it got a brand new 340lph fuel pump that is hard wired to the battery running at 100% all the time, new reg that i have vacuume checked with no leaks
is it possible that the long vacuum reference line could have a pressure/vacuum drop?
looking at logs it does appear to be reference related it starts to drop pressure as boost goes positive and when you come off the throttle it gains 2psi above base pressure for a few seconds
I have tried different diameter vacuum lines from availble ports on manifold but they were all long runs and made no difference

1509joe

iTrader: (2)

As long as you have no vacuum or fuel leaks and your pumps ok and everything is constant that is probably the way it is going to be. Your senders and gauges are not realistically going to be perfect. When getting mapped if there's anything amiss it will show then.

sti.dean

thanks for replying
give or take half a psi it is constant and i have no leaning out issues, although its not helping my high injector duty at high rpm, its just something thats bugged me for a while that i cant find the cause of it and the worry if something is weak it could get worse
the logs are taken from syvecs ecu and deffi sensor, so would have thought they would be fairly accurate
do the figures look fairly normal and nobody really gets perfect boost reference to fuel pressure?
thanks again

Henrik

iTrader: (5)

So if I recall, the vacuum hose for the OEM FPR is a very short bit of rubber hose from just before the injectors - maybe the distance does matter?

Also, if it's an aeromotive/fuelab or similar FPR, maybe the volume of air needed to move the spring is larger (because at least visually the part that holds the diapraghm is bigger), so a thin, long, tube would take longer to equalize the pressure in the FPR vs the inlet?

What happens if you're in a section of RPM where you get boost quickly (i.e. past spool point) and let go of the throttle so you're in negative manifold pressure, and then stomp on the throttle to get max boost as quickly as possible? Do you still see the same lag between MAP vs fuel pressure?

sti.dean

hi
yes same pattern, as boost goes positive fp dips 3psi below base pressure, come off throttle fp goes 2psi above base pressure, straight back on throttle fp dips again.
the vac line is thick walled but i am thinking it maybe expanding under pressure and sucking shut under vacuum. i have just thought of something else i can try, replumb recirc valve vac pipe to another point on the manifold and plumb fpr vac pipe to port on underside of the manifold which is a much shorter run to see if it makes any difference

Turbovin

iTrader: (2)

Do you get any lean spots or hesitation after shifting gears, normal driving or WOT?

I get a lean spot after shifting when driving easily, one tuner suggested I might need fuel pulsation dampers in my fuel lines.

sti.dean

[QUOTE=Turbovin;12091020]Do you get any lean spots or hesitation after shifting gears, normal driving or WOT?

I get a lean spot after shifting when driving easily, one tuner suggested I might need fuel pulsation dampers in my fuel lines.[/QU




i dont get any lean spots or hesitation.
has your car been mapped? it may need a little bit more fuel adding at the bottom of the fuel table,

Turbovin

iTrader: (2)

[QUOTE=sti.dean;12091021]Yes it's been mapped but he couldn't fully get rid of it. I have a Link G4+. I will experiment with fuel lines etc, I have some ideas which may solve this.

scoobynshag

iTrader: (14)

Got mine sorted in the end. Changed all injector seals and engine fuel lines and a new set of plugs and new fuel of course and fired into life instantly. The seals were knackered and the plugs, well let’s say they’ve seen better days and I’m amazed they even worked.