The electric fuel pump supplies fuel at a high pressure to the fuel rail and injectors, this is then regulated by a fuel pressure regulator. Typically, the regulator is not adjustable and is pre-set to a 3 bar maximum pressure. At idle the fuel pressure valve reduces it by 0.5 bar approximately to 2.5 bar. When accelerating quickly from standstill the fuel pressure increases at a proportional rate retaining a lean fuel mixture strength as required by the E.E.C. for new vehicles. However, the resultant effects of the standard regulator can allegedly produce:
lethargic throttle response
occasional drivability problems at slow traffic speeds
intermediate performance 'flat spots' when accelerating
The power boost valve is valve has an adjustable fuel pressure, effected by the movement of an adjustment screw on the crown of the unit. New Power Boost Valves are pre-set with a maximum fuel pressure of 2.5, 3.0 or 3.5 bar, depending on the vehicle in question, and similarly (to the original valve) the fuel pressure is reduced by 0.5 bar approximately at idle. There the similarities end. On acceleration from standstill the Power Boost Valve fuel pressure will increase at 1.7 times the standard rate. This will produce a healthy, strong fuel mixture strength which will instantly improve the drivability of your vehicle, allegedly providing:
instant throttle response
removal of performance flat spots
extra engine performance
The Nismo adjusteable fuel regulator does exactly what is says on the tin. It allows you to control different fuel pressures for given volume flow rates. This allows you, amongst other options, to take the option to increase the fuel pressure to increase A / F ratios if there is no option to increase injector duty but obviously running much higher pressures can be detrimental to the life expectancy of the fuel pump but given the relatively low volume flow rate of the GTS pump other factors need to be taken in to consideration
The reason a fuel pressure regulator is not needed is if the tuner is properly adjusting the injector slope parameter in the ecu mapping for the new injectors instead of just cranking up the fuel pressure...
Saying that I do seem to have a Nismo one it is very shiny
I think I'll be going for the Nismo fuel reg, but how do you set one up for the pressure you want?
Okay before someone jumps in...............
Obviousely with a gauge, but do you have to do it under load or just free revving?
Given that according to the blah the Nismo one suposed to do 2.5bar at idle, rising to 3 bar under load then that would be a good place to start, you need to fit an inline pressure guage in to the system while you are setting the pressure
It might be an idea to make sure have have a wide band lambda sensor or a gas analyser so you can check its not overly lean etc and a friendly tuner on standby to rib you rotten for getting it wrong but will sort you out at short notice
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