2G When to upgrade return lines?

[1000hpgsx]

If I'm right, the fuel pump runs the same all the time and tries to push the same amount of fuel no matter what. Correct? So if my return lines are too small I'll know at idle since later in the rev range the return lines will see less and less fuel?
So basically if I can get my fuel pressure correct at idle I don't have to worry about my return lines just yet?
I just upgraded all my feed lines to -8AN and installed link at the same time. Everything is great so far but I still have the stock pump and injectors.
Thanks

 

[Mauispyder]

You're fine.

 

[1000hpgsx]

So my assumptions are correct? If it's good at idle then it's good? I'm asking because I'll be upgrading the pump and injectors soon. So if you meant I'm fine now then I knew that, I'm just asking in general for when I upgrade. Thanks for your reply.

 

[FIBA M - EC17PSE]

You dont need to worry about the return for a while. you can get a double pump and then return go bigger like 6/8an but you dont need it yet and even then its way up in the nunbers before you need to consider the return being changed.

 

[Paul@RTM]

If I'm right, the fuel pump runs the same all the time and tries to push the same amount of fuel no matter what.

That's correct. The fuel pump setup on these cars is stupid simple. It's either on or off. It never pumps more or less in response to any condition. (Technically, as the voltage to the pump varies the fuel output will vary, but there's no mechanism that intentionally alters the voltage to make use this).

 

[1000hpgsx]

Awesome, that's what I was wondering. So what about my second assumption, if it's good at idle then it'll be good to go since the return lines are seeing the most fuel at idle. Is that correct?
Again, I know I'm good now and I know I'll be good for awhile.

 

[cmehlxl]

read numerous places on here and dsmtalk that the return line should last ~400hp.. what tank to rail kit did you buy or did you part your own together? cost?

 

[1000hpgsx]

I plan to be over that at some point. I pieced my own together. it's -8AN all the way to the rail. I took lots of pictures to do a write up on it later. I've seen different things posted about it but never found a complete how to on the process.
Total cost is $142.82 for the whole set up. I spent a few extra dollars because I have a wet nitrous system which T's into the feed line but obviously that isn't a necessary cost. Even that was only another $25 or so.

 

[1000hpgsx]

I've heard a lot about how my return lines are good and how they will be good but what I'm really after is my above question. If any one knows I would really appreciate it. That is, if the fuel pressure is good at idle then it'll be good to go at all RPMs since the return lines are seeing the most fuel at idle. Is that correct?

 

[Diamond Star Werks]

Fuel pumps runs according to the voltage it receives. It is switched on when the ecu sees a trigger from the crank sensor. Then the speed is determined by voltage and back pressure and wear on the pump. The older the pump gets the more wear it gets and the slower it can and will run. The older wires get the more resistance of those wires build up causing lower voltage on the receiving end resulting in slower rpms at the pump.

On the end of the fuel rail there is a fuel pressure regulator with a vacuum/boost line attached (stock wise there will be a line to the regulator's solenoid from intake and then to regulator itself.).

At idle your pressure will be lower your base pressure. Base pressure is pressure seen when there is no vacuum or boost going to the regulator.

Your pump will run faster or slower depending on the pressure its working against. Higher pressure can and will mean a slower pump.

To answer your question, NO, assumption incorrect. A good fuel pump at idle does not promise a good pump while driving and especially not under pressure. As boost increases so does the pressure on top of the fuel pressure regulator thus increasing fuel pressure. Just because it pumps fine at idle does not mean it will be pumping enough at redline or anywhere in between.

P.S. With a name like "1000hpgsx" I wouldn't think you'd be asking such a noob question. Sorry bout the other people being unable to give you the right answer. Be careful who you listen to.

 

[Diamond Star Werks]

To answer your main question, return lines are like wastegates. You need to upgrade when you are having issues lowering the pressure to the desired rate.

 

[1000hpgsx]

Thanks MJcanada for your reply but you missed the point completely. I already know everything you've said. In my posts after my original post I shorted my question so maybe that's where the confusion is.
My question is not about the fuel pump keeping up, it's about my AFPR and return lines being able to get the fuel pressure low enough.
Example: I plan to upgrade my fuel pump at some point. If I get a big enough fuel pump then the pressure in my fuel lines will be too high no matter what I set my AFPR at because my return lines will be too small.
But lets say that the pump is not too big and I am able to get the base pressure right where I want it. (done at idle) If the return fuel lines are big enough for that pump at idle, will they be big enough for that same pump at all RPM's? I think I know that the answer is yes but I've been wanting someone to confirm this.