Originally Posted by
bodace5
Hi. Fuel pressure at idle was 2.5bar so ive adjusted it to 3bar but once i remove the vacuum/pressure pipe it shoots up to 4bar not 3.5bar? Should i change the pressure regulator? Its an aftermarket regulator thats bolted to the map sensor bracket with an adjuster on the top
You need a standard Weber Marelli fuel pressure regulator set to 3 bar with the vacuum pipe disconnected. Once set, you reconnect the vac pipe.
This vac/boost pipe provides the signal to the FPR to regulate the fuel pressure according to the inlet manifold pressure. At idle the fuel pressure will drop by the same amount of vacuum in the inlet manifold so as to maintain the correct differential pressure. At 1 bar of boost you'd should have 4 bar of fuel pressure.
Because you now have 4 bar at idle you are asking the fuel pump to deliver 1 bar more pressure for the same boost level (5 bar for 1 bar boost), if your pump and wiring are not able to cope you'll run lean and blow the engine.