EVO IV, Vacuum valve for FPR?

[JB9]

Hi. I bought an Evo IV with an Evo VI engine in it a few months back. Has a G4+ plugin ecu.

Today I noticed that the car has a vacuum solenoid valve connected in-line with the vacuum hose to the fuel pressure regulator. Never seen that before, my cars tend to have one hose from the intake manifold going directly to the FPR. Checked the Ralliart workshop manual, and it seems like it actually is supposed to be hooked up like that.

1. Why? What does it do/help with?

2. Do I still need it when the car is on the Link ECU? I can't find anything under Auxiliary Outputs that resembles this valve.

3. If it's no longer supposed to be there, could that potentially cause fueling issues?

 

Thanks.

[Adamw]

1.  I believe they were used to increase fuel pressure on hot restarts.

2. No it is not connected electrically with the Link ECU.

3. I have never seen one cause a problem, but I guess if it got stuck in the open position your fuel pressure would no longer increase with boost.

[JB9]

Thanks for the quick reply. Will disconnect and remove it.

3. Don't you mean if it got stuck in the closed position? That would mean no vacuum control, thus 3bar (or whatever base pressure is on these) all the time?

[Adamw]

21 hours ago, JB9 said:

Don't you mean if it got stuck in the closed position? That would mean no vacuum control, thus 3bar (or whatever base pressure is on these) all the time?

I havent looked at one closely in a while but my recolection is they are a NC valve and when energised they vent the reference side of the FPR to atmosphere - so if stuck open the FPR sees no vacuum or boost reference.