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Discussion Starter · #1 ·
The CIS is now gone. :woowoo: On to the plumbing.
I bought an FPR that is made to work between the pump and the rail. Is there any advantage to having regulated pressure running to both ends of the rail, or should I just plug the end of the rail down by the TB?
 

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Are you sure that thats the design implementation of the fpr? Most I have seen go between the rail and the return line. This eliminates the FPR having to suddenly flow more fuel when needed, and also eliminates the chances of trapped air in the rail (though I suppose once it's been purged there wouldn't(shouldn't) be any air entering the rail. I've heard of some designs with a closed rail though.

Do you have any info/part numbers or such that we could look at?
 

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Discussion Starter · #3 ·
The destructions that came with it state that it is designed to work between the pump and the rail. I called the manufacturer/distributor this morning to ask a different question about it and actually remembered to ask about this as well. The guy on the phone said that I should just hook up to the rail after the FPR and plug the other end of the rail, otherwise I will have all kinds of problems. He did say that most FPRs are made to work after the rail.
It won't give you a ton of info, but here is the page it is on: http://www.injector.com/fuelregulators.php I got the 643, which is a nice part for the money. It is overkill, but I will take that over the other extreme.
 

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I can't see how the regulator would even know where it's located. I mean hello Marren, is it a regulator or not? :wtf: You can install it like they say, but if it were me, I'd run a feed to both sides of your fuel rail so that you're injectors at the far end doesn't see any pressure drop. Then if you're going to do that and have two lines, you might as well do it right and go fuel pump -> rail -> regulator -> return.
 

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Is your return line capable of handling high pressure?

I always thought that the regulator not only keeps the right pressure for the rail, but also allows a "cheaper" return line. In my case I have all SS braided, but I'm not sure in your case.

Cheers,

Carlos.
 

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What return line are you refering too? The one from the rail to the FPR, or from the FPR to the tank?

Rail->FPR is gonna be a high pressure line, as all the fuel after the pump and before the FPR outlet is gonna be the same pressure.

The return line to the tank should never see much of any pressure, unless there's a blockage/crushed section somewhere. :eek:
 

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The one from the FPR to the tank.

That's why one might want to have to FPR after the rail or how are you going to reduce the pressure on this return line???
 

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Huh?? How would pressure ever develop in that line though??

Putting the FPR before the rail doesn't mean that the return line is pressurized. The system is just plumbed a lil different

Bad ASCII art ahead, you have been warned....

Traditional plumbing:
Code:
**High pressure lines** +--->Fuel pump-->fuel filter-->fuel rail-->Fpr --+
**Low Pressure lines**  +-Fuel Tank<-------------------------------------+
Pre-rail plumbing:
Code:
**High pressure lines** +-->Fuel pump-->fuel filter-->Fpr-->fuel rail
**Low Pressure lines**  +-Fuel tank<-------------------+
Does that help, or make things worse? :p
 

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My fuel rail has 50 psi at idle which seems to be correct
If you use model #2 the return line will be pressurized to 50 psi. Can it handle it?

Cheers,

Carlos.

ps. Fuel tank to Pump is low pressure. At least here on Earth (1 atm).
:wink:
 

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CS_Rally said:
My fuel rail has 50 psi at idle which seems to be correct
If you use model #2 the return line will be pressurized to 50 psi. Can it handle it?
No. it's not pressurized at all. The return from the fpr just dumps back into the tank. what restriction is on the other end of the line (at the gas tank) to cause a pressure increase???

Think of it this way, the fpr return line doesn't _have_ to go back to the tank, you could connect a garden hose to it and let it pour out onto the ground, but there would still be 50psi of fuel pressure behind the fpr outlet. Sucks for gas mileage tho :p

ps. Fuel tank to Pump is low pressure. At least here on Earth (1 atm).
:wink:
You guys live on Earth?? :?
 

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:D
 

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Two notes:

There shouldn't be a dP/dx (assuming steady state conditions), as the injectors are connected in "parallel" with the rail....I'd have to dig out an example problem from my old Fluid Dynamics book to provide a more in-depth answer.

Fluid exiting an open line/pipe almost always has the same pressure as the ambient conditions. Now, it can get tricky if the line outlet was submerged, but even then we would just assume that it had the same pressure as the fluid body.
 

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Discussion Starter · #15 ·
Well this has certainly answered any and all questions I had. :) Thanks to all for the lessons in hydrodynamics.
 

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Here are a bunch of links to pages on fuel systems:

http://www.dune-buggy.com/turbo/fuelsystem.htm

http://www.rotaryextreme.com/fuelreserv ... system.jpg

http://www.2gnt.com/www/corbin/8inj.html

http://www.icarumba.com/includes/conten ... Fig22.html

http://forums.probetalk.com/showthread.php?t=1701087590

Personally I would have the FPR after the rail, to make sure that each injector is seeing "exactly" the same fuel pressure. "Exactly" is in quotes, because you will see some pressure drop because the injectors are firing, but it should be negligible.

Lucas
 
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