lq4gp

I am new to the turbo world so I am hoping someone out there can answer my fuel delivery questions. I have a 1987 Grand Prix with a lq4 that is currently carbed. I will be going to a fuel injection system out of a 2001 chevy truck. My question is, is it necessary to boost reference a fuel system? I was planning on running a gsl392 walbro fuel pump, but have been told that it is only capable of 60psi. Aren't the factory fuel systems on ls equipped vehicles set to 60 psi? Is the reason people boost reference a fuel system is so that they can run a smaller injector and still get the fuel flow needed when under boost? If I can maintain 60 psi and have the properly sized injector to make the horsepower I want to make, will I have any problems? Any help would be appreciated.

ws6fitz

It isn't something you need but is highly recommended. Its a safety factor that makes it safer to run boost. You have a much higher chance of going lean and going boom if you don't have a boost referenced system. The way I look at it is if you are spending the money to run high horsepower on the car don't cheap out on it now. It will cost you a lot more for a new motor than it would to but boost referenced regulator, return line if you don't have one and a bigger fuel pump.

lq4gp

What do you suggest then for a different pump? Aeromotive A1000 sounds like it will deliver, my only reservations are that I read I have to install a voltage control module if I run the car on 10 gallons or less or if I run the car for more than 30 minutes at a time. This is a street car so both of those things will happen. The other thing is I will either have to put a different pickup in the stock tank or install a fuel cell. Is this my best option?

parish8

iTrader: (6)

it depends on your hp goals. if your running big injectors like 160lb units it helps with tuning to lower the fuel pressure at idle and raise the fuel pressure at max boost. in reality you are just keeping the pressure across the injector the same.

compare that to a non return set up where you see the most pressure at idle and the least at max boost. that large injector is going to be flowing a ton of fuel at idle when you do not need it and tuning for it might be difficult and at wot it will be flowing the least when you could actually use it.

with lower hp goals where the mildly modded fuel system(drop in pump and even a boost a pump) can flow enough fuel i see no reason to change to a return system. it does not make it any safer or less likely to blow up.

parish8

iTrader: (6)

i just read your first post closer. do you plan on running the factory truck fuel bucket with the built in regulator? i just want to make sure you know there is a regulator with a "return" it is just all located right in the gas tank. you cant just run that 392 pump without any kind of regulator.

lq4gp

No I will not be running the truck bucket. This fuel system will have to be completely redone as the car has the fuel lines all set up for a non return low psi carb application. I know I will need a regulator to run it, now im just concerned that a gsl392 wont deliver enough to make my horsepower goal of 600rwhp. Do you run higher than 60psi usually when your under boost? Or is it a matter of if you can maintain 60psi so your flow stays adequate?

parish8

iTrader: (6)

the exact fuel pressure doesn't matter it just happens that the factory regulator is set to ~60psi.

since you are not starting with anything you might as well build a traditional fuel system with a front mounted regulator and a return line. i would go with a little more pump too. i really like the holly twin pump. it might be a little more than you need but it is quiet, pretty, flows a ton of fuel, reliable. it is unlikely you will stop at 600hp.

parish8

iTrader: (6)

there are other considerations. how do you plan on tapping into the tank? with a carb it isn't as big of a deal if it sucks a little air every now and then. with fuel injection at can be a very big deal especially on a boosted set up. even when not floored lets say braking at the end of the track the car could die or a sharp corner it could die.

lq4gp

Does anybody ever run two pumps in parallel to the regulator? My initial plan was to run two of the gsl392 pumps out of the stock sending unit (modified of course) and run separate lines all the way to the regulator. Of course if you can run a single holley twin pump or an a1000 that will flow enough it wouldn't make much sense. I just thought it might be an alternative.

lq4gp

I was just going to pull out of the factory sender that just has a pickup tube placed in the bottom of the tank. What are your suggestions?

parish8

iTrader: (6)

multiple 392's were very common. i have done it several time. the biggest reason was the large pumps were not reliable and made a lot of noise. i still do not trust an a1000.

i dont know what other large pumps kick *** but i have used the holly one a couple of times now with lots of hours with no issues at all. it is nice to be able to stage the pumps. it reduces aeration, fuel heating.

twin 392's would get you where you want to be. i would y them right after the pumps. put the pumps right at the back and have a separate feed to each pump. the holly pump would not need any y's and not cost much more.

parish8

iTrader: (6)

i dont know what you are working with so it is hard to say. i just know it sucks having to worry about the pick up getting uncovered.

lq4gp

Explain what you mean by staging. What my plan was if I ran twin 392s was I would check valve both pumps and then run one off of a microswitch, either based off fuel pressure or throttle posistion. Then only one pump would run the all of the time. It would also allow me to get home if one pump failed.

HexenLord

If you're going to check valve them, you wouldn't need to run another one off of a hobbs switch as it wouldn't backflow if it failed.

parish8

iTrader: (6)

Staged is just what you are taking about. Typically on a boosted set up you run one all the time and one is triggered at a certain boost level often with a Hobbs switch. Those pumps have a one way valve in them so you do not need to add one.

95bowtie

I've been using a magnafuel 4303 on my setup for two summers now. I've ran a good 500 gallons of e85 through it without issue.

You can hear the pump but I wanna say it's about half as loud as a a1000 and you don't need a speed controller for it. My gas tank will get slightly warm to the touch after a good beating on a 90*+ summer day but I haven't had any issues with it so I guess it is at an acceptable temp.

Like others said just build a normal fuel system with return and a 1:1 ref. Regulator.

I've never messed with a pickup tube like you are thinking of using but I know I weld on sump pickup for the stock gas tank would be a better option I would think. Should cost less than a fuel cell for the trunk but work just as well.

The Alchemist

iTrader: (19)

Just a personal experience, I'm running twin in tank walbro 255s, and have ID1000s, and I'm still using the stock regulator. I made 740rwhp and maintained fuel pressure without an issue. True, you have to biased the VE table due to the decreased overall pressure (Rail pressure - manifold pressure), but I was still only at 78% injector duty cycle, and was extremely rich, ie, sub 11.0:1 afr. Before anyone screams that being that rich isn't good, I know, I was in process of tuning it, then the winter hit, and we've had snow mutliple times already. I will slowly lean it out when the spring hits and get afr's back into the mid to high 11s.

Point is, I'm still on the stock regulator, and doing fine.

9sectruck

iTrader: (9)

I have my car set up to run on a 255 in the stock tank bucket then a sump off the bottom of the tank to a 4703 magnfuel pump.

the car runs and drives off the factory set up, at 5psi the big pump comes on along with the factory pump still running,

all ran through a after market 1:1 regulator,

just put a check valve in the feed line to the rails before the t from the stock fuel line.
works like a charm