Your inline FPR is dumping excess fuel back into the main feed line which carries a 52psi pressure. That excess fuel is pressurized just as much as what the second pump is pumping. You are not scavanging anything but increasing a unknown amount of fuel pressure in your completely fuel system. Like I said, yes, you got your fuel rised. And No, it is not safe.

 

The system will run and maintain any set amount of fuel pressure between 52psi to the fuel pump max. And it will quickly return to the base FP when the pump is either shutdown of the FPR resets to base. The system can even be used to maintain the feed presure or maintain a lower pressure if the in tank pump can keep up with it's intended pressure supply.

If there is anything wrong with the Nissan fuel system for high power output it would be the quick connect to the fuel tank.

 

Last night I recieved a few PM's about plugging the stock FPR.

For those of you that don't know my car has been at Crawfords for several weeks getting a new makeover.

Doug told me today he plugged the stock fpr by 1) pull fpr out of tank 2) epoxy the holes closed 3) let it dry and 4) stick it back in the tank. For those concerned, the epoxy is not effected by gas. (Doug has obviously has done this before). He told me a secret about the o ring too. He said that it will not increase in size unless you get gas on it.

Quick question, it seems like the stock idle fuel pressure is 50 psi. The consensus also seems that the fuel pressure should increase 1psi fuel per 1psi boost. So in my case at 10psi during wot, the fuel pressure should be 60psi?

 

Yes this is correct. It took me a while to understand why it was REALLY necessary to increase FP as boost increases. Turns out the fuel pressure is effected and dependant on the positive pressure that the turbo is producing in the manifold and air intake track. Without a FP raiser, you actually have less TRUE fuel pressure at the end of the injector as it sprays into the intake track. So if your guage reads 60psi, and you are boosting 10psi, your effective fuel pressure is really 50psi.
Thats why the FPR raiser compensates for that by 1:1

As stated, the ECU doesnt have a fuel pressure sensor. The in tank FPR is a tiny POS integrated into the plastic Fuel Pump assembly. There is no way it can dump enough fuel at the levels necessary when running a Walbro 255. And even if it could, you should still ditch it for an external raising rate FPR.


SR20, I understand your diagram now..I think. But seems like a very risky band-aid. You are creating a continues loop of high pressure fuel running back to the FPR. Definatley not even close to text-book F/I fuel management.

A better, and almost as easy solution is this:

1) Install Walbro 255
2) Plug Stock FPR
3) Cut fuel line before the fuel rail.
4) Install Aeromotive A-1000 FPR.
5) Return line back to the tank, and drill small hole in the plastic FP assembly for the return.

Now, obvously not as robust or expensive as ACP's plan...but a much safer alternative to the solution you proposed.

 

That answered my question. The Ecu from Honda K series motor goes bezark if the fuel pressure is alittle higher or lower. It also has a returnless fuel system.
I can understand why it's sensitive to change of fuel pressure because with no fuel return and to get a ultra clean emission the fueling must be precisely accurate. If the fuel pressure changes, reprogrammed fueling would be thrown off.

 

Evo, you are exactly correct.

The returnless system was born out of ever-more-stringent emmissions regulations. With a return system there is fear that the warm fuel will return towards the tank and possiblity release some vapors into the atmosphere. Instead, with our returnless system, the vapors would return to the intake manifold straight away, or be routed from the evap canister back to the intake manifold.

Damned the EPA!! and CARB!!

 

I have the Walbro 255HP and have never had any problems with the stock FPR. The pressure remains constant. Even when I used that booster system the stock FPR had NO problems quickly venting the excess line pressure back into the fuel tank when the pump was shut off. I monitored this with a Autometer electric full sweep fuel pressure gauge.


It seems to me that the returnless system was designed also as a cost reduction factor because of it's fewer parts. Also, since no fuel is returned to the tank the fuel always remains much cooler which is better for consistancy in power levels and avoiding detonation.

 

installed my return line.
Here is the bulkhead fitting, on the top of the driveside fuel assembly




Put a hose on the end of the fitting, so it goes into the tank


Picture of it back together
*note, I didn't have to use the 180 degree fitting, I only did so because I had it. It didn't work on the Aeromotive like I thought, as it would turn around and hit it.


And the MagnaFuel fitting, with the lines going to towards the fuel rails, waiting on my adaptors

 

wonderful!

 

tim: good job getting it from paper to the real application!

 

couldn't of done it without your help buddy!

 

Impressive.

 

ACP,
Any good word on the FPR plug? I haven't been reading your posts lately, sorry for my lazyness.
Thanks,
MIKE

 

No change on that.....

page 2 of this thread

 

Thanks ACP. Your design is looking awesome. Did you mention that this could possibly be sold as a package deal one dayl?

 

Here is the compressed hard line fitting



Installed on the car



Heatsheild I installed to protect the fuel lines.


My return line, run above the driveshaft, very secure

 

I like the heat shield and location of running the return line. You are really paying great attention to all the details.

good work!

 

Thanks gg

Do you recognize the heat sheild piece ?
You probably have it in your garage..
hehe

 

hmm...I'll have to search my inventory...cant really think of where that part came from. Oh...did it have something to do with the stock exhuast system! Oh yes...I think it did! But too bad I tossed it!

So how is the install coming? Have all of your fitings and adaptors come together?

 

I was wondering where you got the piece that goes in the fuel rail so I can try to make my own as well. I'm trying to set up my fuel system like yours w/ the 2 feeds and coming out the front into the fpr and one return. This is the only missing piece