Whats the Deal w/ the return line???
06-15-2008, 01:32 PM
#1
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Whats the Deal w/ the return line??? If the stock Camaro T/A style fuel pump has a built in regulator, why does it have a return line that goes to a T fitting in the feed line? I don't understand how this could possible work. Can someone please explain?
06-15-2008, 03:16 PM
#2
My understanding is the regulator is on the return side of the pump hat assembly, so the fuel go through the pump, through the filter, through a T, and the remainder gets returned to the tank, through the regulator, and dumped back into the tank,.
the "T" allows fuel to go to the rails, without pumping it all the way to the front of the car, to go back.
Ryan
the "T" allows fuel to go to the rails, without pumping it all the way to the front of the car, to go back.
Ryan
06-15-2008, 05:05 PM
#3
My understanding is the regulator is on the return side of the pump hat assembly, so the fuel go through the pump, through the filter, through a T, and the remainder gets returned to the tank, through the regulator, and dumped back into the tank,.
the "T" allows fuel to go to the rails, without pumping it all the way to the front of the car, to go back.
Ryan
the "T" allows fuel to go to the rails, without pumping it all the way to the front of the car, to go back.
Ryan
06-15-2008, 09:15 PM
#4
This was done so that the system compensates for the fuel filter restriction. Since no hot fuel is returned from the rails, there is less evaporative emissions to deal with. I'm sure this, plus the cost savings from eliminating a fuel line, was the major reason to do this.
Unfortunately when you increase power output, the added restriction of the factory fuel line is not compensated for & pressure starts to drop at the engine.
When in doubt, add a front mount regulator. You will start to see the pressure drop at the engine with over 600rwhp, but it really starts to be a problem over 700rwhp, with a rear mount regulator. The place to put the regulator is where you intend to control the pressure... at the engine.
Unfortunately when you increase power output, the added restriction of the factory fuel line is not compensated for & pressure starts to drop at the engine.
When in doubt, add a front mount regulator. You will start to see the pressure drop at the engine with over 600rwhp, but it really starts to be a problem over 700rwhp, with a rear mount regulator. The place to put the regulator is where you intend to control the pressure... at the engine.
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06-19-2008, 10:16 AM
#9
Lonnie, you say it becomes a problem at 600rwhp, but I'm having problems with only 525 rwhp. Is it because Im fi? I'm still using the factory lines and only upgraded the fuel pump (walboro 340). At this point its hard to say if its a bad fuel pump, the heat of the 9 inch and hooker catback, or the fact that I'm the unluckiest person when it comes to cars.
06-19-2008, 07:01 PM
#10
A single intank pump is your problem in the 500-550rwhp range depending on the brand/type of kit. Above this power level, the pump is insufficient to support the flow.
Once you get enough pump, the line/rear mount regulator will be the next hurdle. Typically the pressure will drop due to the line restriction even though the pump(s) can flow enough. This is noticeable around 600rwhp & becomes a problem around 700rwhp. Then you really need a front mount regulator. This way the pressure can remain stable & the injectors can perform at their full potential. At this power level, it is usually best to do the lines at the same time.
Once you get enough pump, the line/rear mount regulator will be the next hurdle. Typically the pressure will drop due to the line restriction even though the pump(s) can flow enough. This is noticeable around 600rwhp & becomes a problem around 700rwhp. Then you really need a front mount regulator. This way the pressure can remain stable & the injectors can perform at their full potential. At this power level, it is usually best to do the lines at the same time.
08-04-2008, 03:40 PM
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I'm hijacking this thread since it's been idle for a little over a month... 
What would happen if you were to hook a vacuum/boost line up to that nipple on the regulator in the picture? Just curious because I stumbled across THIS while searching for boost dependent FMU info. Scroll down to "Free FMU" and see what that guy found when hooking a vacuum/boost line to his stock FPR nipple by accident. That'd be pretty cool if the stock FPR worked that way!
Also, I have a cartech 20005i boost referenced FMU that I was wondering about integrating into my STS setup. Would I be able to disconnect the return line coming off of the T block and plumb my FMU in between the block and the stock FPR to raise fuel pressure under boost but maintain stock pressure in vacuum?
What would happen if you were to hook a vacuum/boost line up to that nipple on the regulator in the picture? Just curious because I stumbled across THIS while searching for boost dependent FMU info. Scroll down to "Free FMU" and see what that guy found when hooking a vacuum/boost line to his stock FPR nipple by accident. That'd be pretty cool if the stock FPR worked that way!
Also, I have a cartech 20005i boost referenced FMU that I was wondering about integrating into my STS setup. Would I be able to disconnect the return line coming off of the T block and plumb my FMU in between the block and the stock FPR to raise fuel pressure under boost but maintain stock pressure in vacuum?
08-06-2008, 09:31 AM
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Hey, I just noticed you're in Pittsburgh too...neat.
There's a serious lack of performance places in this town. 
08-06-2008, 02:55 PM
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Hmmm...perhaps I should just stick with the idea of using a rising rate FMU. Nate or Lonnie...do either of you know if plumbing in a rising rate FMU like I mentioned would work or not? Thanks.