I believe the standard fuel pump generally pumps at a slightly higher pressure than is needed by the injectors - hence, the need for pressure regulators. The pbv basically lets ur car have more fuel when it needs it - don't think that it is explained that well below but its all I have found:
http://www.eliseparts.com/shop/index.php?m...products_id=582
HOW DOES THE POWER BOOST VALVE WORK?
The 'Power Boost Valve' is a pressure regulator, designed for use on 'electric fuel injection' engines as used on your Lotus. It has a special fuel enrichment facility for acceleration, commonly known as a 'Rising Fuel Rate' and simply replaces the original equipment valve fitted to your fuel rail .
Simply explained, the electric fuel pump supplies fuel at a high pressure to the fuel rail and injectors, which is then regulated by a fuel pressure control valve. This original 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 valve produce these drawbacks:
· lethargic throttle response
· occasional drivability problems at slow traffic speeds
· intermediate performance 'flat spots' when accelerating
By comparison our Power Boost Valve has an adjustable fuel pressure, effected by the movement of an adjustment screw on the crown of the unit.
Power Boost Valves are pre-set with a maximum fuel pressure of 2.5, 3.0 or 3.5 bar, depending on the vehicle engine tune 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 so Fuel Pickup will also be 1.7 times faster than standard.
This will produce a healthy, strong fuel mixture strength which will instantly improve the drivability of your vehicle, providing:-
Quicker throttle response
Elimination of throttle hesitation & removal of performance flat spots
Faster acceleration
Extra engine performance
The regulator enhances engine performance on acceleration by enriching the mixture strength. On constant throttle and cruise conditions the valve returns to a normal regulator function so you have normal fuel economy on light throttle and normal idle RPM is retained.
The Power Boost Valve is simple to install and basic fitting instructions are provided. These units are mechanical and are considered maintenance free.
This technology has been around for quite some time.