Ok I bought and installed a Walbro 255lph pump. Has anyone noticed unusual fuel pressures? I'm at 52-56 at WOT rather than 42 like before. Not to mention that with the N2O I'm at almost 90psi.

 

That's not unusual because the Walbro is a high-flow/high-pressure pump. If you want to lower your NA WOT fuel pressure, you need a fuel pressure regulator like a SARD, AEM, Aeromotive, etc.

 

Yeah that is what i had to do. I go a weaponr one for like 100 bucks.

 

Will it effect my Gas Mileage or A/F ratio? Any bad effects about this being so high?

 

It would hurt both. Mostly at WOT.

 

So if someone had a 255lph pump on an NA car and dynoed, would you say the HP would be less or more? If that cant be answered would the a/f be more rich or lean?

Only reason I ask is I too have a 255lph pump in my tank but that is only temp for 2weeks before the boost goes on. But however Im dynoing the car tommorow.

Dixit

 

Will find out for sure today at the dyno.

Dixit

 

Ok big debate here.

If the injector only lets so much fuel in each firing how can a higher pressure of fuel cause you to run so rich? I guess since its a computer controlled and adjusted it wouldn't be as much of a variable.

 

Hmm, never thought about that. This is a valid point.
I am not an engineer and I dont know what i'm talking about, but maybe this is how it goes.

The injectors and their subsequent systems (ECU fuel map, and etc) are designed to work with stock fuel pump (meaning stock fuel pressure). I dont think there is a fuel pressure sensor in a maxima. The ECU and the fuel maps assume there is adequate fuel flow all the time at a set fuel pressure. So if you go WOT and the ECU tells the fuel injectors "Ok give 5 shots of fuel" per second or whatever, but since you have higher fuel pressure than normal, each shot contains more fuel than what the fuel map assumes.
I dont know how fuel systems work in a car and this is just a thought, so dont gimme no flames !!

 

Guess you wrong there. Dynoed the car today and I was on the lean side. Not rich. My chart was near 14.3-13.5 all the way to redline. That is no where near rich territory.

Dixit

 

I am wrong The original question was about Louie's car. Louie stated he was running 52-56 at WOT. You are tell me that he's not running rich when the OEM spec is 43 psi? Did you state what your fuel pressure was after the Walbro 255hp fuel pump install? No, I didn't think so. Maybe your 5th gen was able to maintain OEM fuel pressure spec with the Walbro 255hp. I never said your car was running rich. I said Louie's car was running rich. How do you think SC guys, turbo guys and dry manifold nitrous guys get their extra fuel from?

 

I got my car smogged with the high flow pump and no aftermarket FPR and passed with flying colors, so I don't think under normal conditions, the new FP causes any decrease in milage or ill effects. My $.02

 

Think of injectors as on and off switch. Maxima ECU doesn't have a fuel pressure sensor. When injectors opens for 1 sec, it's assuming you are at 43 psi at WOT.

Example A: 1 second at 43 psi = X amount of fuel
Example B: 1 seccond at 56 psi = Y amount of fuel

Do you think X = Y?

 

I don't think the smog inspecter was doing WOT on your car. Beauty of a modern car is having an ECU, O2 sensors and various other sensors. During open loop mode, ECU can adjust the fuel injectors to the optimal fuel economy/performance via the O2 sensors to a certain point. I'm sure if you are running 90 psi at idle, your car won't be running.

 

Your are right there. BTW I wasnt "calling you out" by saying you were wrong. Just thought you generally said you would run richer, and just said that seemed wrong after the dyno. But I do understand the example you gave earlier.

Dixit

 

Okay...no biggie.

 

my a/f monitoring on my dyno was off the chart rich. So I guess its a timed thing as tony stated.

228fwhp 282lb tq
700lbs of n2o pressure