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Blood for Blood
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I used google .... you should google 1st then search button then post.

A fuel pressure regulator is a small device with a diaphragm inside that maintains a constant pressure (or tries to) regardless of the rate of flow. Basically you can put any fuel pressure in, and get a constant "set" pressure out - however much the input pressure might vary. So a Fuel injected car for example has a pump that might run at anything between 150psi static, and 50psi under flow conditions in use. This is "regulated" by your fuel pressure regulator to (usually) 45psi constant (3 bar).


The fuel pressure regulator (FPR) maintains a constant pressure across the fuel injectors. That means the fuel line pressure (at the top or entrance of our injectors) minus the intake manifold pressure (at the bottom or exit of our injectors) is a constant, regardless of engine speed, or manifold vacuum or boost pressure. The FPR connects to the intake plenum using a vacuum hose. When there is vacuum in the plenum, the FPR lowers fuel line pressure 1 psi for every 1 psi of vacuum. When there is positive pressure in the plenum (turbo boost), the FPR increases fuel line pressure 1 psi for every 1 psi of boost. The FPR maintains fuel line pressure by controlling the amount of fuel that returns to the gasoline tank. To increase pressure, the FPR creates a restriction, reducing the amount of fuel that flows through it back to the tank.

The installation of an aftermarket fuel pressure regulator allows for the adjustment of fuel pressure to suit larger aftermarket injectors and other engine modifications. They are also necessary to regulate and flow increased volumes of fuel pumped by high flow aftermarket fuel pumps.
Fuel pressure regulator, which works with the fuel pump to maintain a steady pressure relationship between the fuel line side of the injectors and the intake manifold.
Most adjustable regulators are still one to one or close to that, however you can adjust the pressure at idle or full throttle for fine tuning. There is one other type of regulator that is used with aftermarket forced induction. These are rising rate regulators commonly called FMU's (fuel management unit). These regulators increase fuel pressure at a multiplication factor of boost. So instead of messing with complicated computers and injection duty cycles, these systems just increase fuel pressure to add fuel. They go inline down from the factory regulators and only start to add pressure under boost. So when you are off boost, you maintain factory tuning and drivability. Only as you get boost does the FMU begin to increase fuel pressure

Most modern fuel injected cars run a fuel pump in the tank and run much more fuel than is needed to the fuel rail. A regulator keeps a certain amount of fuel pressure in the rail and then sends the rest back to the tank.

Your car as well as most fuel injected cars have a one to one fuel regulator. It varies the fuel pressure by 'watching' manifold pressure. It uses a diaphragm to control pressure. Most Nissans at idle (vacuum) fuel pressure is 34psi and at full throttle (No vacuum in theory) 43psi. If you further put pressure (turbo or super charger) to the manifold, it further increased fuel pressure. In factory regulators, for every pound of boost, it adds a pound of fuel psi. Hence 1 to 1.

Most adjustable regulators are still one to one or close to that, however you can adjust the pressure at idle or full throttle for fine tuning. There is one other type of regulator that is used with aftermarket forced induction. These are rising rate regulators commonly called FMU's (fuel management unit). These regulators increase fuel pressure at a multiplication factor of boost. So instead of messing with complicated computers and injection duty cycles, these systems just increase fuel pressure to add fuel. They go inline down from the factory regulators and only start to add pressure under boost. So when you are off boost, you maintain factory tuning and drivability. Only as you get boost does the FMU begin to increase fuel pressure.
 

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...The fuel pressure regulator (FPR) maintains a constant pressure across the fuel injectors...
That's not true. The FPR maintains a constant line pressure. There will allways be a drop accross the injector.

That means the fuel line pressure...is a constant, regardless of engine speed, or manifold vacuum or boost pressure.
AND

The FPR connects to the intake plenum using a vacuum hose. When there is vacuum in the plenum, the FPR lowers fuel line pressure 1 psi for every 1 psi of vacuum. When there is positive pressure in the plenum (turbo boost), the FPR increases fuel line pressure 1 psi for every 1 psi of boost.
contradict themselves. the second statment is correct. fuel pressure is dependent on plenum vacuum/pressure.

other that the two things i pointed out - good job on the explanation.
 

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^ great job on not reading my title at all...

you kinda owe me an apology here. read my title...
I didn't think you would have coppied it straight from google. Anyway, i'm sorry. I wasn't trying to give you a hard time. I just wanted to make sure there were no missunderstandings. My bad.
 
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