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Discussion Starter #1 (Edited)
People have been asking for my version of the fuel return so here it is:


So today even though I’m busted up from surgery I decided I would finally finish my fuel system. I had pretty much been done and just awaiting some new parts from Hybrid Racing.


There are a lot of parts involved in doing a full fuel system with return line. This process is not cheap. I’ve seen people spend up to $1k in just their fuel setup. I believe I spent almost $600 myself. Here are some of the parts.. I know I’ll be missing some misc…

After Market Fuel Rail
Fuel Pressure Gauge
Fuel Pressure Regulator
Inline Fuel Filter
Aftermarket Fuel Pump
30ft -6an Fuel Line
3/8” and 5/16” submersible fuel hose
lots of AN fittings (I’ll explain all I used in the DIY steps)
Hose clamps
Zip Ties


Here is what I can remember for the fittings I used...

Straight -6an fittings [4 Total]
-Pump (1x)
-Filter (2x)
-FPR (1X)

45* -6an fittings [2 total]
-Rail (1x)
-FPR (1x)

90* -6an fittings [1 total]
-Rail (1x)

-10an to -6an adapter [2 total]
-Filter (2x)

-8an to -6an adapters [4 total]
-Rail (2x)
-FPR (2x)

90* male to male fitting [1 total]
-pump (1x)

-6an to 3/8th nipple [1 total]
-pump (1x)

-6an plug [1 total]
-FPR (1x)




So lets get started…. The first thing you need to do is install your new fuel pump. I already have a DIY on installing a pump without a return. So start with this DIY to take out the pump and modify the cage
http://forums.clubrsx.com/showthread.php?t=738511



Now lets start the new process!
So I started my new fuel setup today.

Basically I pulled the pump back out. I already had a 255lb pump installed. But now I'm adding a new feed and return setup. So first I dismantled the fuel pump assembly



Then I went and place the nut on the bottom where I will be drilling. You will need this nut. You will also need a 90* male to male 6an fitting to go through the pump. Also I used a 6an to 3/8” barb fitting inside the pump. You can see the fittings in the picture above.


Then I drilled out the hole. I used a blade to clean up the burrs and etc


Now I placed my new fitting threw the hole





Now I attach the barb connector and redo the hoses. I use the stock feed nipple as the return now and the pump goes to the new added barb fitting.




And put the pump back in the tank. Now to start the lines....

First thing I did was mount my inline fuel filter. First I wanted to wrap it in hose so it doesn't vibrate





The using wire I mount it under the car where I wanted it



Now start by putting your line from the pump. Here is the first straight -6an fitting used. Run the hose down to under the car to the fuel filter.
 

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Discussion Starter #2
and make a marking where to cut the hose to the fuel filter. Then make a cut



Now put your other end on


and now put your first half of the fuel line up and tighten it down. You will need -10an to -6an adapters if you use the same aeromotive fuel filter.


Then using the hose clamp I secured the hose down.


I decided to stop using stainless braided hose and bought russells black braided hose.


I started with the longest distance. So I began by adding a straight -6an fitting on the hose


and then connected it to my FPR. If you want to put your FPR where I did here is my FPR bracket DIY
http://forums.clubrsx.com/showthread.php?t=759243

So anyways, connect another straight -6an fitting to the hose and start from the bottom of the FPR which is the return



Then used clamps and started routing it down and around the header back over to the passenger side




and wrapped it behind some of the wiring harness. I also zip tied the fuel line every chance I could just ass added protection
 

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Discussion Starter #3
Then I cut the stock feed line back where you can't see it and zip tied the return line to it all the way down the frame...




Then put the hose through up to the pump and measured and cut where needed


You also need to remove the quick release clip


I then clamped it down to the stock feed output. It fit extremely tight and I could barely get it on so I have faith.... also this is the return so it has a lot less pressure.



then I attached another AN fitting and started from where I had left off at the fuel filter



I then brought it up towards the transmission and moved it up towards the rail.





Now I put the rail on and fittings so I can mark where to cut the line. Now I make my mark on the hose and cut.


Because this is going to be seen I don’t want to scratch the fittings. So I blue tapped them


 

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Discussion Starter #4
Now I attach the line to the first side of the rail.


and now I attach the FPR fitting and measure up the next cut





cut and add the fitting… almost done!


attach the line



BAM!!! Now you are done!





here is a small diagram



**I probably missed some things and I’ll edit the thread if needed**
 

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Boosted Goose
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Nice D.I.Y.
 

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61 ci now
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stock RSX fuel system uses a single fuel line to the stock fuel rail, it pressurizes this rail to stock fuel pressure of 43-47PSI. It has an un-adjustable FPR in the stock fuel cage in the tank.

When you add boost to any engine, you need to be able to increase fuel pressure to match what the intake manifold/supercharger manifold is seeing. For example, if you put 15PSI into an engine, the stock fuel system is pushing fuel at 43psi. So the engine side of the fuel injector is seeing 15psi, so now you're down to 28psi on the fuel rail. 43-15=28psi. The less fuel pressure provided to the injector, means the injector needs to stay open longer to provide the needed fuel to the engine. More boost = larger fuel requirement. You can start to see the problem here.

your injectors will run a much higher duty when in boost with the stock fuel system. Even with an upgraded pump you won't get around this.

when you add a return line and a 'full fuel system' you provide much more fuel to the fuel rail at all times, also the fuel pressure regular will increase fuel pressure at 1:1 rate. You run a boost line from the intake manifold into the fuel pressure regulator and as intake pressure rises, the outlet hole in the FPR gets smaller, thus making the fuel trying to escape become more pressurized. Any excess fuel that the pump is pumping from the tank returns back into the tank to make the trip again.

I hope this better explains it for everyone.

nice DIY :)
 

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Discussion Starter #9
stock RSX fuel system uses a single fuel line to the stock fuel rail, it pressurizes this rail to stock fuel pressure of 43-47PSI. It has an un-adjustable FPR in the stock fuel cage in the tank.

When you add boost to any engine, you need to be able to increase fuel pressure to match what the intake manifold/supercharger manifold is seeing. For example, if you put 15PSI into an engine, the stock fuel system is pushing fuel at 43psi. So the engine side of the fuel injector is seeing 15psi, so now you're down to 28psi on the fuel rail. 43-15=28psi. The less fuel pressure provided to the injector, means the injector needs to stay open longer to provide the needed fuel to the engine. More boost = larger fuel requirement. You can start to see the problem here.

your injectors will run a much higher duty when in boost with the stock fuel system. Even with an upgraded pump you won't get around this.

when you add a return line and a 'full fuel system' you provide much more fuel to the fuel rail at all times, also the fuel pressure regular will increase fuel pressure at 1:1 rate. You run a boost line from the intake manifold into the fuel pressure regulator and as intake pressure rises, the outlet hole in the FPR gets smaller, thus making the fuel trying to escape become more pressurized. Any excess fuel that the pump is pumping from the tank returns back into the tank to make the trip again.

I hope this better explains it for everyone.

nice DIY :)


wow that was very impressive. I'd rep you if I could :bow:
 

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Ok I understand that the engine needs more fuel pressure under boost. But I don't see how adding a return line increases pressure. Stock system pumps from tank and dead ends at fuel rail correct? Wouldn't the dead end build pressure? I'm not arguing here just trying to learn, I don't see how creating an exit for the fuel helps increase pressure.
 

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Registered
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Adding the return line didn't increase pressure, spaz's aftermarket fuel pressure regulator is doing that. The stock one was bypassed and the return line was added to bring unused fuel back to the tank. You are correct in saying the stock fuel rail builds pressure, but its pressure in the wrong direction, everything behind the rail would have high pressure, but the engine would not see that as the stock rail is an obstruction at this point.
 

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61 ci now
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correct, the stock system cannot be adjusted by boost pressure to add more pressure. That is what we are doing when we install a full return fuel system in the RSX.
 

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correct, the stock system cannot be adjusted by boost pressure to add more pressure. That is what we are doing when we install a full return fuel system in the RSX.
Oohhh ok. That makes sence to me now.
 

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NooB Sibot
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455 Posts
NICE write up dude...
I need to do this while am going supercharge....
- just a noob question: did you change your fuel rail as well?
 

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Super Moderator
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Discussion Starter #19
NICE write up dude...
I need to do this while am going supercharge....
- just a noob question: did you change your fuel rail as well?
I've changed my fuel rail 4 times...

stock -to- BDL -to- Ktuned -to- Hybrid Racing :rotfl:
 
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