[b0xdesigns]

Fuel Pressure Regulator...What exactly does regulating the fuel do?

I saw "NISMO Fuel Pressure Regulator" @ nissan perf. parts and theres no description...

Anyone know?



Thanks..

B0x

 

[mgthe3]

The fuel going to your injectors is under pressure. The pressure regulator......regulates the pressure, the injectors don't need what the fuel pump can put out.

 

[b0xdesigns]

So does it help with the Mpg?

 

[GripperDon]

Constant fuel pressure

The injectors regulate the amount of fuel going into the engine to acheive the desired A/F ratio that varies somewhat according to temp, maniford pressure, spark timing etc. The way they do this is to regulate the width of the electrical pulse that opens the injectors valve. THe "Map" of the desired injector pulse width assumes a given fuel pressure. as the combination of oriface area, pulse widthe and pressure all work togetherr to determine the amount of fuel that will flow thru the injector. The regulator does it's best to keep that a constant value regaurdless of the fuel pumps output and demands for fuel.

 

[GMTURBO43]

From a performance catalog - I'd guess it to be an adjustable FPR. This allows you to increase the fuel to the injectors to make up for any mods that have been made i.e. intake, exhaust, turbo...

You can kind of 'tune' your fuel needs to the mods. This isn't an exact science - but it is better than leaving it at the stock level.

If it isn't adjustable - I'd say it has a higher base fuel pressure than the stock - NOT lower. This will not make mileage any better - in fact I'd say the opposite. But performance MIGHT be better with more fuel if the correct mods are made.

 

[GripperDon]

Actually it is an exact science

Please see the previous post. The performance map is only "Trimmed" by the Lamba or as it is commonly call the Oxygen sensor. to modify the pulse width sent to the injector. Air fuel ratio and spark timing effect to the greatest extent power and emissions.

Leave the pressure regulator alone. The Manifold air flow sensor or MAP sensor as it is sometimes called will provide input to the computer to produce the appropiate injector pulse width.

 

[GMTURBO43]

I was referring to using the FPR to 'tune' your car. You are far better off doing it through the computer if you have the capabilites - or letting the stock computer (ECU) handle it.

You could get to a point where pulse width isn't going to keep up with the fueling needs - although there really aren't enough mods available to the Murano where this is going to be an issue.

I agree - there isn't a need for an FPR on the Murano.

MAF = Mass Air Flow Sensor
MAP = Manifold Absolute Pressure

Completely different things.

 

[Eric L.]

I was referring to using the FPR to 'tune' your car. You are far better off doing it through the computer if you have the capabilites - or letting the stock computer (ECU) handle it.

You could get to a point where pulse width isn't going to keep up with the fueling needs - although there really aren't enough mods available to the Murano where this is going to be an issue.

I agree - there isn't a need for an FPR on the Murano.

MAF = Mass Air Flow Sensor
MAP = Manifold Absolute Pressure

Completely different things.

Yeah I think GripperDon was referring to the mass air flow sensor.

 

[Stoker]

One thing to remember is that fuel injectors have very tight clearances that allows them to increase the feul pressure in the fuel injector. This high operating pressure also increases the heat devolped in the injector. There is always more fuel going to the injector than what is required. This excess fuel actually cools the injector so that it does not overheat and seize. The excess fuel is returned to the fuel tank to be used.

It is not a good idea to fool around with your fuel system as it was engineer to work a specific way to maximize fuel efficency.

 

[GripperDon]

AF vs Pressure

Not completely different things. I refer you to the old vacuumn gage. When the buterfly or throttle control valve (call it what you want) is open the pumping action of the engine creates less vacuumn in the manifold as the valvel is open and it lets air into the mainfold. Therefor the pressuure in the mainfold rises as the air flow into the manifold increases. Before we used both the pressure and Flow MAP was used alone, now days we use both for even more precise measurement. The MAF densors are usually hot wire or vane type and respond to flow taking into account both air density and velocity.

 

[GMTURBO43]

Same purpose - different way of measuring it.

 

[GripperDon]

Now you got it!

 

[Eric L.]

On my 97 Maxima I remember reading in the FSM that yes the vehicle has both MAP and MAF sensors, but the MAP sensor is only used for diagnostic purposes and does not directly affect engine performance. In other words, the primary input for air/fuel mixture is the MAF sensor.

I think in the a 2003+ Murano, this is most likely the case too. GripperDon is correct in that the MAP sensor was once used for this purpose, but today, the MAF sensor is the only input which the ECU actually uses between the two to optimize engine performance.

Why is the MAP still there? I believe it is used today as a part of the emissions control system to monitor for vacuum leaks within the intake system.

 

[Eric L.]

Update - looked in the FSM - doesn't seem like the Murano has a MAP sensor. Makes sense, since in my previous post it seemed from what I had written that Nissan had stopped using the MAP sensor for any meaningful purpose at least as far back as 1997.

 

[GMTURBO43]

I did have it before.

There is a difference between MAP and MAF - however they are used independant of each other. On a MAP equipped vehicle - it is easier to let the ECU do the adjustments.

I still go back to my first statement - there isn't a need for a AFPR on a Murano

 

[loggerdude]

MAP SENSOR

I am thinking the map sensor is perty inportant part of the fuel calculation.
http://minimopar.knizefamily.net/ecu/map_se.html

Check this site out.
I no you can change your your fuel rate by changing sum sensors
Most of the sensors run from 0-5 volts. The water temp should stay at about the same voltage. the other sensors are changing based
on throttle postion.I Have seen sum guys change the water temp
you can change that voltage to get more fuel over the hole operating range Thats one of the things that hyperchip duz.
they put a lower termastat. from 195 down to 180 or 160 .this will
give you more fuel.
This mite be a little off topic.
This is my 2 cents
Loggerdude