morris

iTrader: (2)

The scenario is that as you hit the accelerator fuel pressure drops this is before you even get into boost. It goes from a starting point of 45 psi to as low as 30 psi or so as you are acelerating. Prior to the dip it will go up a few PSI. If you sit and rev the enging though it will go up some. (ie no load condition)

So I am trying to understand how a booster pump works for the fuel system. If the walbro isnt able to supply enough volume of fuel to the injectors how is a booster pump going to help. I mean if the walbro cant feed the injectors how is it going to feed the booster pump?

jgscott

iTrader: (1)

That sounds like a FPR issue to me. I think the fuel pump, pumps the same PSI regardless of acceleration.

Its the FPR that controls the PSI to the injectors. So I thought.

morris

iTrader: (2)

Nope I swapped out the fpr and the same thing continued to occur. My guess is that the injectors are flowing more fuel than the walbro can supply at the required pressure.

Or a remote possibillity is that the stock fuel line is restricting the amount of fuel that can get to the injectors.

ebydrc

a booster pump is normally used for when the primary pump is able to move the amount of fuel needed (volume) but isnt able to keep up with the pressure demand. in that case some would run a booster pump (walbro inline aeromotive sx, etc) to assist the primary. however that has the potentiol to stress the primary into premature failure. most fuel pumps have a kind of "checkvalve" and when they fail it no more fuel. which is bad at WOT @ 35psi. a inline pump would help, but isnt the best solution, it would be nice to see your fuel setup or specs, idealy you should have larger diameter lines into the fpr and smaller out of the fpr and that acts kind of like its own sump. that would be what i would firstly say you need to do. also if that doesnt fix your problem upgrade to a fuel system that keeps up with your demands rather that be twin inline walbros running from a tank sump or a single weldon.

david

USAF_RT

I ran an MSD / ACCEL inline booster on a stock pump for over 4 years with no problems. This was a varying 40psi idle to 85psi under boost. The main downside would be the noise...a Weldon would be a good choice, if you have the $$..and I am not sure how easy the twin Walbro's are on an SC, but that would also be nice...but external booster pumps work fine as well...I know tons of bolt-on turbo kits for cars that run this type of setup (when they use a RRFPR), to avoid messing with the stock pump too much...just gotta make sure your fuel lines are all the appropriate sizes, and you don't have any strange restrictions anywhere.

ebydrc

rrfpr's are horrible and just a cheap bandaid. twin inline walbro are no big neal in any car. its take some labor pulling the gas tank for the sumps and all that fun stuff. weldon aeromotive and sx are all awsome pumps. fuel assits work but is a weak point in the fuel system.

USAF_RT

Well technically I swapped from a RRFPR to a 1:1 with an additional injector setup...but this was not for my Lexus.

And it's not exactly a band-aid if your goals are moderate it works quite well...but yeah it is if you are going for crazy power levels...so I somewhat agree

Anyways yeah just saying that booster pumps do work, they are just noisy...and depends on how crazy your power goals are.

morris

iTrader: (2)

Well I have a turbo gs400 running 11psi right now but would like to go back up to 17-20 psi.

I have a single walbro hipsi pump in the tank feeding the stock fuel line and stock fuel rails. There is a single return from one of the rails to an aeromotive fpr and back to the tank the return is all -6.

I dont think it is a volume problem if it were then my pressure would drop to almost zero, so it looks like it may be a psi problem which the booster pump may help.

I was thinking about running dual walbros (last resort) but a single pump should be able to do the job in terms of volume

ebydrc

check into a larger fuel rail and lines. did i read that right your fpr is on your return line?

ebydrc

i agree they do work but, its far from a good solution imo. but none the less they do work.

mitsuguy

iTrader: (2)

i don't care about psi, but what kind of horsepower are we talking here? What injector size and duty cycle?

that will be a bigger determining factor than anything...

Those little Walbro's are tough, I've seen single Walbro cars make 600 hp at 30 psi boost (74 psi fuel rail pressure)

morris

iTrader: (2)

at 11psi I am around 400rwhp at 17 I was at 500 I am running 440's, duty cycle with 440 should be fine I have run 11psi on 310's before.

the fpr is on the fuel rail opposite the supply side so it maintains the pressure on the rail.

As to the fuel rail size, the stock one should be able to handle the current hp.

IT could be the fuel line but then that would effect volume and not pressure so the symptoms would again be different. ie almost no pressure not just low pressure. At least that is what it looks like to me.

ebydrc

there is a reson why people setup there fuel system in graduating (sp) line sizes, it helps agaisnt that intial fuel pressure dip

jgscott

iTrader: (1)

This maybe a Dumb question but........ did you try adjusting your " Adjustable fuel pressure regulator " it is adjustable for fuel pressure. Sorry if it's a dumb question.

mitsuguy

iTrader: (2)

stock lines should be ok for 500 hp, not ideal, but ok...

I would look into possible issues with the pump itself, maybe wiring to it (not sure the gauge of the stock wiring), or possible the seal between the pump and the fuel line...