[utahphunk]

I've searched extensively on what seems like a pretty simple question, but I haven't found any definitive answers.

I'm looking to install a longer fuel hose from my stock FPR to my stock hard line (to solve the "GR stumbles at 2500-3200rpm" issue.) Everything in this area is stock. I know I need a simple fuel line tool to remove the quick-connect on the hard line end. I'm thinking the cheapie plastic ones from Harbor Freight should do the trick.

Once that's off, what else do I need on the quick-connector side? The stock connector has a crimped metal piece on it. Will I need to hack out the fuel line side of the quick connector to re-use it or should I just buy another one? I haven't been able to find a part number for the quick connector. Two different local Autozone-ish places had squat, too.

Edit: Pic:

 

[scoob r u]

Don't re-install the connectors... Bad idea.

Use a barb fitting, OR, buy new replacement quick-connects. The QCs aren't cheap though, when I last looked they were $20+ each.

 

[utahphunk]

Don't re-install the connectors... Bad idea.

Use a barb fitting, OR, buy new replacement quick-connects. The QCs aren't cheap though, when I last looked they were $20+ each.

Thanks for the reply.

So I'll use a disconnect tool to remove the connector, throw away that fuel line and that metal fitting, then just get new fuel line and use one of these in the end of it?

Dorman Fuel Line Connectors - SummitRacing.com

Basically, the black plastic Dorman quick-connector on that site will replace all the metal (and the green plastic) in my photo, right?

 

[scoob r u]

Something like that... Not sure about that brand, but if the size is right, go for it!

That's a lot less expensive than I remember...

 

[red2012STI]

IAperformance sells a kit specifically made to solve this issue. The funny thing is that my car was running perfectly smooth with just the Stage II OTS but since I added this kit(fuel pressure lines/regulator) and had the car tune with 1100cc injectors , DW 65, Grimspeed and custom tuned my car now stumbles on its face at that rpms

Subaru Fuel Pressure Regulator and Damper Kit

 

[utahphunk]

IAperformance sells a kit specifically made to solve this issue. The funny thing is that my car was running perfectly smooth with just the Stage II OTS but since I added this kit(fuel pressure lines/regulator) and had the car tune with 1100cc injectors , DW 65, Grimspeed and custom tuned my car now stumbles on its face at that rpms

Subaru Fuel Pressure Regulator and Damper Kit

There's about a 50/50 split of people that have success from that kit, and people that have no change with the kit. The simplest solution is actually extending the fuel line as I'm doing. It seems like this solution (and the 100% success rate it has so far) has just come up on here, nasioc and romraider in the past month or so.

It turns out that the problem is caused by a resonance wave (or standing wave, I'm not sure I'm using the correct term) in the fuel line at certain RPMs, for larger-than stock injectors. I believe there's also load compensation data in the stock tune indicating Subaru has done work to tune around the mechanical issue. Doubling the size of the injectors means you and I are making the mechanical problem way worse and therefore, way harder to tune around (which is what a lot of people have been working on for a while.)

Thanks for the link, though. I was pretty close to just throwing the $200 at the problem. Even with my modest 350whp 20G-XT setup, I have to very deliberately drive around the flat spot. Otherwise, the car lurches and makes me sad.

Edit for interesting trivia: The plumbing term for what is happening in the stock fuel line in this situation is called water hammer.

 

[rube23]

Are you extending both the return and supply hoses? you mentioned the hose to the FPR which should be the return. Unless im mistaken, the pic above looks like the supply line.
can you take some pics of what you end up doing and the parts? I wouldnt mind giving it a shot to see if it helps, tuning definitely took care of most of the stumbling but its not 100% as I would like it to be.

Thanks!

 

[utahphunk]

Are you extending both the return and supply hoses? you mentioned the hose to the FPR which should be the return. Unless im mistaken, the pic above looks like the supply line.
can you take some pics of what you end up doing and the parts? I wouldnt mind giving it a shot to see if it helps, tuning definitely took care of most of the stumbling but its not 100% as I would like it to be.

Thanks!

I'm definitely extending just the supply hose, which is what I've taken a pic of. It sounds like I said FPR when I was actually referring to the fuel dampener? Whatever is the stock piece that the supply line comes out of (and heads straight to the hard line, as pictured) and looks like it has a plastic jimmy hat on the top of it.

EVERYBODY SHUT UP I TOTALLY KNOW WHAT I'M DOING.

Will post pics when I'm done.

 

[rube23]

Also, i think once you get that quick connector off, you might find that you have enough hard line to install a fuel hose on it and clamp it down......negating the need for a barbed quick connect. I cant verify that though since ive never taken it off. but if its anything like the wrx one you should have plenty. Check out pics at this link.

How to remove fuel disconnect? - Ultimate Subaru Message Board

 

[rube23]

I did a little search, looks like you wont need any type of quick fitting with a barb after removing the stock inlet line, kinda looks goofy though with all that extra fuel line just coiled up. I wonder if a universal fuel filter tapped into the stock inlet line would serve the same effect to reduce the resonance wave. I might try both out...

see pic at middle of page linked below

RomRaider • View topic - How to fix the GR STi 2400-3200 stumbles

 

[utahphunk]

After buying (but not installing) the parts this morning, it does look like all I really needed was the fuel line and the same simple metal clamp that's on the other side of the line.

As for adding a universal fuel filter: I'd think a longer fuel line is a better solution because it's simpler, cheaper and will never clog. I wasn't psyched about that coil, but if it resolves most of the drive-ability issue, I'll be too busy hauling ass to even think of it.

But yeah, that RomRaider thread has been my jam. You can even see my retarded "plz help!" post at the end there. Kind of a bummer that it took a few days for the mods to approve that.

 

[rube23]

After buying (but not installing) the parts this morning, it does look like all I really needed was the fuel line and the same simple metal clamp that's on the other side of the line.

As for adding a universal fuel filter: I'd think a longer fuel line is a better solution because it's simpler, cheaper and will never clog. I wasn't psyched about that coil, but if it resolves most of the drive-ability issue, I'll be too busy hauling ass to even think of it.

But yeah, that RomRaider thread has been my jam. You can even see my retarded "plz help!" post at the end there. Kind of a bummer that it took a few days for the mods to approve that.

What size and length fuel line did you purchase?

 

[utahphunk]

What size and length fuel line did you purchase?

3 feet of this fuel injection line: NAPA AUTO PARTS which sounds like a lot of length but does end up looking like it. (TWSS)

I got the standard inner-diameter for the stock fuel lines: 5/16"

 

[rube23]

cool, im interested to see how it works out. i'll probably try it out next week or so.
Which tool are you using to remove that line? I looked up harbor freight and found this, looks like it should work.

6 Piece Fuel Line and A/C Quick Disconnect Tool

 

[utahphunk]

cool, im interested to see how it works out. i'll probably try it out next week or so.
Which tool are you using to remove that line? I looked up harbor freight and found this, looks like it should work.

6 Piece Fuel Line and A/C Quick Disconnect Tool

That's exactly what I got. Haven't used it yet, but I'm now 99% sure it's what I need. Although, I think you can just break the green plastic quick-connector thinger off if you're not going to re-use it anyways.

As you can tell, I'm figuring out things as I go along.

 

[rube23]

Im sure you already know this, but remember to release the fuel pressure before taking off that line unless you want a 93 octane bath. Pull the fuel pump fuse from under hood while the car is running and let it stall out. You should be good to go after that!

 

[Avrgmike]

OP, just a side note for you. i recently did this 4 days ago using 2' of 5/16" fuel line i bought from a local pep boys auto center. coiled it all around i believe there was 3 coils, although i left oem connection intact and just tied into oem hose w/ a barbed coupling then onto feed line dampener. beware of using the normal fuel line from generic auto places. My extra line actually burst with in 4 days. Not sure whether it was do to being coiled up and extra pressure on that hose, i had 3 zip ties loosly keeping it coiled, or just bad luck. the generic hose labeled as fuel line did not have a psi rating or anything on it. i replaced today actually when it burst on start up w/ heavy duty gates fuel line, it is the 4AN braided fuel line and rated to 300psi. and only has 2 coils between the connections.

i also read that some people have taken the oem feed dampener off and either used a inline tee for the connection of feed and balance line. and others have removed feed dampener and used barbed coupling, and capped off balance line going to return fpr.

As you stated i also heard that the kits you can buy sometimes didnt help peoples stumble issue, and i dont have the $ atm to do a complete fpr setup w/ parallel rails, which also will solve this stumble problem. Hence why i went searching all over till i found the same write up on rom raider, and went the cheaper route for the time being.

either route you go keep an eye on the fittings and fuel line coiled up, mine was very soft after i removed it almost like it had been stretched and broke the internal reinforcement.

also please keep us all posted on the route you go, and update after awhile so others can also have options and feedback on this.

and remember to pull fp fuse in the fuse box under the hood, remove fuel cap and run car till it dies to relieve as much of the pressure as u can, you will still have some so have a towel wrapped under all the lines so fuel dont spill down your motor and fuse box. but it does stop after a few seconds.. when all done replace fuse tighten fuel cap and prime the fp a few times to check for leaks b4 starting..

 

[rube23]

based on your comment that it didnt have any psi rating on it and that it was very soft when you removed it, you probably ended up purchasing something other than fuel line.....and the fuel broke it down causing it to burst.
on another note, did it have any effect on the stumbles for you?

 

[Avrgmike]

the line i originally had purchased was labeled on tag and on the hose itself as 5/16" fuel line.. yes it cured the stumble issue completely. although i do not feel comfortable leaving it that way forever, due to being a temp band aid. it does seem to work extremely well for the time being and as long as there is no other side effects all shall be ok. this is however just my opinion. i do plan on replaceing the known 08 fpr and dampener flaw after the holidays and winter..

 

[utahphunk]

OP, just a side note for you. i recently did this 4 days ago using 2' of 5/16" fuel line i bought from a local pep boys auto center.

Sounds like you bought normal fuel line/hose when what we need is fuel injection line/hose, which is rated for much higher PSI. The stuff I got and linked a few posts up is fuel injection line rated to 225 PSI.

I'm curious why you would spend $200 to swap in a FPR and fuel dampener when the extra-long fuel is actually the solution that works. The GR's FPR and dampener work fine otherwise. *shrug*