When using the Walbro 255, i understand the limitation is actually the stock regulator in the tank. So why can't i just bypass that in-tank regulator, and install a rising rate FPR somewhere near the fuel rail...inside the engine compartment? I see this done all the time on F/I Hondas and acuras.

Is the return line absolutely necessary to maintain proper fuel pressure? What am I missing here??

 

This is was Spazpilot did... as an integral part of him eliminating the e-manage altogether.

 

The elimination of th eManage is not related to the fuel system. The TS reflash and eManage will have very similar fuel requirments.

 

Exactly, the fuel control comes from the reflash...

To back that, is the pump, which increases fuel pressure as boost increases through the FPR.

 

Unfortunately the return line is required for a FPR to work. Even the one in our tank has a return line of sorts but it's already in the tank so it just bleeds off the excess right there. Because all it does is pinch the flow of fuel flowing through it thus causing high pressure on one side. Once the pressure reaches the set value it over comes the spring and diaphragm and the excess fuel will trickle pass into the return line back to the tank. The great part of FPRs are that they so simple most only have 5-6 parts in them.
Gary

 

How easy is it to bypass the in-tank FPR? I thought it was built in to the fuel pump assembly? Also by bypassing this will there be any repercussion? Will the ECM look for this?

 

you can not bypass the stock FPR in the tank. What happens is that the walbro will end up overpresserizing the stock regulator. The FPR your adding is not to control the flow up top but mainly to keep is from adding to much fuel (70psi) down at idle. If your trying to add more psi then 58psi (8 above stock) you will have to plug the stock regulator not remove it. You will see what I mean if you lift the fuel pump assembly out. It is all glued and peaced together with the pick up pump. My regulator reads 50psi during normal driving and rises to 58,59psi during boost. If you want anything more I would then suggest a bigger pump (inline), or bigger injectors with a reprogram of the emanage. I was doing some test when I relized that at wot the walbro could only keep 58,59 psi. this is with my setup. if you have bigger injectors, like the 440's, the main goal of the FPR will not to use it as a pressure riser, but to just maintain pressure consistantly. Doing the math at 52psi the 440 injectors are good up through 500rwhp. So the goal for the greddy guys using the emanage is not increase pressure but maintain it from dropping. hope this helps CJ

 

So spaz, what kind of regulator should I use, and where should I locate it? Do I still need the return line? My goal...like you said, is to maintain between 50-58psi of fuel pressure thorughtout the power band.

 

I am using the aeromotive a1000-6 and located right next to the fuel pump and you will have to run a return line. I got a great deal for 130 if you want to know drop me a pm and I will let you know were I got it from. Spaz

 

Thanks CJ. Just to clarify you are using the Walbro then correct? The set-up you have sounds promising since the problem with the stock seem that pressure drops off. Your set-up seem to maintain pressure throughout the powerband.

 

350Now: correct. I am using the walbro GSS342 255lph high pressure pump. It requires some modding to the clip that holds the pump in place.

 

Thanks CJ. So a Walbro in-tank replacement and then an aeromotive a1000-6 to control the Fuel Pressure. Pretty good idea. Thanks for you reply.

 

I am a little confused. With the in-tank walbro pump and no other modifications, there is a constant fuel pressure at idle of around 58-59 psi. With this setup the fuel pressure still dropped (for me) to below stock levels when boosting. I ended up going with an inline pump to keep constant pressure.

So did you remove the stock FPR and control the fuel pressure with the aeromotive FPR, or do you still have the stock FPR in place?

Also, did you just run the return fuel line off the aeromotive FPR and back into the tank?

Sorry for the confusion (and questions), but I would rather have a mechanical fuel setup rather than the electrical one I have now.

 

with the walbro and no external regulator, the pressure of the fuel jumps to 70psi at idle. That is way to rich. Now at WOT and no regulator the fuel pressure will start to drop to 58psi. In other words because you start using the fuel, the factory internal regulator starts to catch up but still never gets there. stock fuel pressure on the car is 50psi give or take a little. the reason you add the external FPR is to maintain 50 psi at idle with the large fuel pump. The reason I use the riser portion of the regulator 1 to 1 psi boost for fuel is that is the way TS programs the ecu. If you are using the greddy emanage I would suggest just maintain a constant 52 or 54 psi accross the board and adjust the injector pulse. the return for the regulator dumps right back in to the tank. Two option here drill a hole in the tank and get a welder to put a return or (what I did) drill a whole in the plastic top for the fuel pump assembly and buy some earl fittings to make a return there. As for a machanical fuel setup I am not sure what you mean except for like a engine driven pump. That would require a lot of work considering no one makes one for this car.

 

I know int eh testing Ultimate has been doing on their kit, even the 255 with a regulator and return line and 440cc injectors was still producing pressure drop at WOT under boost..they switched to a new fuel pump (Walbro, different part number which I unfortunately am not at liberty to disclose), and its been working great now for several months....all still controlled without a reflash, just an E Manage

Adam

 

Hi Adam, with the new fuel pump are they still using a regulator to control pressure down low? Or just fuel pump and no regulator that keep constant pressure across the rpm band?

TIA,
Jeff

 

Thanks spazpilot.

When I say mechanical I mean rising fuel pressure with a FPR rather than the DFMU I am using now.

For the return line, I was just going to tap into a fuel line that also drains into the tank.

As far as pressures, I guess I can't compare because my idle pressure only rose to 58 psi with just the pump. Under boost I was dropping below 52 psi though.

My setup is ok for now. I might make the switch if I can't fine tune the fuel curve with my current setup and the e-manage.

 

pimp, maybe your Maxima has a different fuel system design...or different fuel capacities and requirements...casuasing to only have 58 a t idle instead of 70. Just a thought.

 

Yeah, thats what I figured when I saw the differences. Thanks GQ. Its hard to compare things with the Z, but thats all I can do for now until we start getting other boosted 3.5L Maximas.

 

They are using a standard 1:1 regulator on their car. I forget the brand, but I am partial to the Aeromotive ones. You most defiantely do not want constant pressure across the band with a forced induction setup.