Atomic

iTrader: (42)

So given an adequate pump both systems are equivalent? Why is there a preference for one over the other?

wkdivr

iTrader: (8)

With the return system, you get more consistant fuel pressure, because you have the regulator right at the rail. With the returnless, the reg is in the tank with the pump (it's actually the same reg, just no vac hookup). You get some fluctuation with the regulator that far from the rails. As long as you're not going lean, or dropping a TON of pressure, you can tune for the slight drop, and be alright. If you're going for big boost, and big power, then you will have to bite the bullet, and switch to return style. Keep in mind, though, there's a TON of engineering in the fuel bucket to keep it full of fuel when the tank is low. Also, the buckets are not even close in size between the 03-down, and 04-up, so you can't just swap out to the 03-down, and be done with it. Also....................the evap system is different, there's more "stuff" on top of the unit, making it harder to mod. It can be done, it's not impossible, but you gotta decide if it's worth the effort.

cheyenne383

iTrader: (25)

Well I already have a couple of smaller pulley set ups I was going to try once I got the 3.4 stock set up adjusted in... but if I'm going to end up re-doing the EVAP, adding fuel lines and a lot of other BS.... it may not be worth the trouble though... ugh.

therock

iTrader: (2)

I'm getting 7 psi with a 3.4" pulley.

I like my PLX wide band and boost setup..

wkdivr

iTrader: (8)

I've pushed mine about as far as I can. Radix'd 5.3; cam; headers; trans; 3.1 pulley making about 10 pounds of boost. My new combo is going together right now (see sig), and I'm going to get it running on the current fuel system, then...........that will be addressed next.

For you........I would recommend doing a fuel pump hot wire set-up,(along with the Walbro pump upgrade), then experiment with cams, pullies, and small stuff, and have some fun. It's fun.......but addicting.

wkdivr

iTrader: (8)

You'll be ok with the returnless set-up for awhile. Get a wideband, and fuel pressure gauge first before anything else.

BigTex

iTrader: (16)

No they aren't equivalent. Since the return style raises fuel pressure above normal operating pressure to compensate for boost, it will deliver more fuel (all things being equal).

Real world: with a return style setup, you would probably see 65psi fuel pressure under decent boost. With a returnless, you wouldn't see more than 58psi even with larger lines and upgraded pump. (given that both were set for standard 58psi pressure) So the return setup can supply more fuel in an even comparison.

My 03 SSS ran just fine on the stock 42# injectors @ 7psi because they flowed more under boost. An 04 SSS would run out of fuel sooner because the fuel isn't boost/vacuum referenced, making them flow less comparatively.

Atomic

iTrader: (42)

Why does the pressure fall off when using a returnless? Just because of the physical distance between the regulator and rails?
Is there any easy way to immediately spot which system an engine is using?

Stoichiometric

iTrader: (10)

The pressure you are after is the differential between manifold pressure and fuel rail pressure. When you go into boost the return system should raise the fuel rail pressure 1:1 to compensate for the increased manifold pressure. The returnless does not do this and your differential pressure is dropping as boost increases. One more thing to note is the pump will likely deliver less volume of fuel as the pressure goes up. Less fuel pressure will allow the pump to deliver a bit more fuel, but with less pressure you will need larger injectors.

thunderwagen

iTrader: (3)

I ran my 05 return less at 8# on an lq9 and only fuel issue I had was I was maxing out the 42# injectors. My truck with a walbro 255 was getting 68psi fuel pressure and 64 under full boost.

I have run just over 500 rwhp on the turbo with the same pump and 60# injectors. For your setup you will be fine with the return less and 42# injectors.