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Super Moderator
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Discussion Starter #21
Were did you get all the fittings and the hose from?

I personally don't like buying fittings online until I know exactly what I need. So I actually just bought all the fittings and the line from a local machine shop. I must of swapped and returned and re-bought fittings several times.

But summit and jegs are a good place to get fittings.
 

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Vendor
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I had the chance to put one of our DW301s in the RSX fuel pump assembly we have here at the shop.

The pump flowed around 20-25LPH less @ 40psi flowing through the OE fuel pump assembly and the internal pressure regulator opened at 48psi and the flow was reduced significantly to ~200LPH.

This really shows the limitations of the OE fuel system, as any boost over 8 psi is really going to hurt your fuel flow.

200LPH @ 40 psi should be good enough to supply 800cc injectors but they will flow just a little less as they are rated at 43.5 psi. @40 psi (8psi boost) 600cc injectors only flow 575cc, good for about 300hp and 800cc injectors flow ~760cc, a little over 400hp.
 

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:dontknow:
i did this today and i dont know what s the problem the car dont start tomorrow i gonna cheak everything but i dont put the regulator that was conected i only left the cable that was together with the fpr that is in the tank???
i dont put it beacuse i think u have to remove, rigth????:dontknow::dontknow::dontknow:
 

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Discussion Starter #32
:dontknow:
i did this today and i dont know what s the problem the car dont start tomorrow i gonna cheak everything but i dont put the regulator that was conected i only left the cable that was together with the fpr that is in the tank???
i dont put it beacuse i think u have to remove, rigth????:dontknow::dontknow::dontknow:


What?! English please. I left my stock FPR in the fuel pump housing because you are bypassing it.
 

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No i removed the FPR in the tank put and aftermarket FPR and did the return line and the car start rigth now i have other problems error code p0134 its say sensor 1 no activity detected i am searching for the sensor here BUT THANKS FOR THE REPLY!!!!!!!
 

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Addicted Tuning Tweaker
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A few issues

So, 20' is about 5' too short for a return line system. Also, in a turbo car you need more like 30' because you need room to route around the hot parts under the hood.

I put mine in and there is a problem that I wasn't expecting. Depending on your fuel cage configuration you will either A) Not be able to run an upgraded (higher flow) fuel pump any less than about 60psi OR B) you will starve your motor of fuel under heavy accelleration and your car will run out of gas when it gets to a quarter tank.

Here's the explaination:

1) The original (in tank) fuel cage/pump assembly:
a) The pump sits in a plastic container "bowl" that has an opening at the rear bottom.
b) The cage is inside the tank and when you add gas the gas enters the hole and fills the cage. Thus surrounding the fuel pump with gasoline.
c) The fuel pump sucks up the fuel and pumps up through a short in tank hose to the bulk head. (The Plastic "top" of the assembly that you can see under your seat).
d) The bulkhead fills with pressurized fuel from the pump and has two outlets. 1) the quick connect fitting for the fuel supply (to engine) line that you can see from the top and 2) an outlet that allows fuel to flow back into the cage.
e) It is this return that is the culprit. It allows fuel from the pump to make its way up the the bulkhead, then when there is too much fuel (pressure) the excess "over flows" back to the tank. It doesn't go straight back into the tank. First it goes into a pressure regulator where it pushes on a spring loaded valve. If the pressure is too low to overcome the resistance of the spring no fuel flows back to the tank. When the engine is running the fuel pump is always supplying more fuel than the engine can consume so there is always an overflow. When you are at idle the engine is consumming only a very small amount of fuel so almost all of the fuel from the pump is going back to the tank. When the engine is under heavy load and requests a lot of fuel more fuel flows to the engine so the spring pushes the valve closed a little. In this way the valve maintans a constant "pressure" relative to the spring force. This does not allow the fuel pressure to fluctuate with air pressure changes (or anything else for that matter).

2) Post fuel system install:
a) You have disconnected and removed your original fuel pump->to->bulkhead line and added a new fuel feed fitting.
b) You have connected your new pump to your new fitting so the bulk head has been "bypassed" in that it does not fill with fuel and therefore fuel does not get split between the tank and fuel supply line any more. Instead the fuel goes straight from the pump to the fitting to the NEW supply line to the motor.
c) As the fuel goes straight to the motor we must provide a way for the excess fuel to get back to the tank. After the fuel gets to the motor we have installed another fuel line that goes back to the tank. Somewhere in this line we put the fuel pressure regulator which acts as a fixed resistance.
d) The new fuel pressure regulator works the same way the old one did. It has a spring that prevents fuel from passing it. Once enough fuel (pressure) has built up it begins opening and allowing fuel to pass back to the tank. Once fuel has passed the regulator it is a straight shot (there is no resistance) back to the fuel tank bulkhead.
e) This DIY connects the return fuel line to the connector on the bulkhead that was previously as the fuel feed for sending fuel to the motor (and back to the cage). Since we are now "backflowing" fuel into the bulkhead it has two paths to take. 1) Out the in-tank connector that used to connect to the fuel pump. It is now connected to nothing. 2) Out the in-tank connector that goes to the old fuel pressure regulator. Once the fuel returns from the engine and fuel pressure regulator to the fuel tank bulkhead it must take one of these two paths.
e.1) If the fuel tries to go through the old fuel pressure regulator it will hit the spring valve and be stopped. Since the fuel has another outlet (dumping out from the top of the tank) that has no restriction, the fuel will take this path instead.

The problem:
- The original in-tank fuel pressure regulator/return was designed so that all excess fuel was shot at high velocity straight back into the fuel pump cage. As the fuel tank fuel level drops below the cage (below the pump) the excess fuel that was returned is shot back into the cage which keeps it full and the pump completely submerged even when the tank is empty. You can run your car all the way to empty because the design of the nozzle on this return "grabs" any nearby fuel (like the small puddle left at the bottom of the tank) and shoots it into the cage along with the returned fuel. If you do run like this your can will sputter and run terribly lean as the cage runs dry at half a tank in a turn or under accelleration or braking. I logged 18.9:1 for a quarter second the other day in a fourth gear accelleration before I figured out what was going on! That is just asking for serious engine damage.

- If you don't use the original return system your pump won't stay submerged when you are low on gas (like a third of a tank). You can remove the spring from the old pressure regulator and plug the original fuel supply connector on the bulk head to force the fuel to use the original return path.

The other problem:
- The original nozzle is designed to create high velocity at a much lower flow rate than an upgraded fuel pump (like my walbro 255lph). Thus it is too small for my new pump. The fuel is ejected at too high a velocity and the nozzle is too restrictive which has the unintended side effect of creating back pressure all the way up the fuel system. In my car this meant that at idle there was nothing I could do to drop my fuel pressure below 60PSI!

The only solution:
- Custom make a bigger return nozzle and plug the original fuel feed connector.
 

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Breast inspector by appt.
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So, 20' is about 5' too short for a return line system. Also, in a turbo car you need more like 30' because you need room to route around the hot parts under the hood.

I put mine in and there is a problem that I wasn't expecting. Depending on your fuel cage configuration you will either A) Not be able to run an upgraded (higher flow) fuel pump any less than about 60psi OR B) you will starve your motor of fuel under heavy accelleration and your car will run out of gas when it gets to a quarter tank.
good info if I ever decide to add a return line (probably not). I did replace my fuel pump with a walbro, but I went with the 190 as I was also concerned about the extra pump pressure with the 255 that I don't need with my set-up.
 

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I'm using this same set up basically but I'm confused on how to set the FPR, should it just be set at around 50 psi, then just hook your boost line up from the manifold and your good? Or is there more than that to set it up?
 

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Discussion Starter #40
I'm using this same set up basically but I'm confused on how to set the FPR, should it just be set at around 50 psi, then just hook your boost line up from the manifold and your good? Or is there more than that to set it up?
I would start around 60psi. Hook the FPR vacuum up to any vacuum line from the manifold.
 
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