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Old 09-03-2011, 11:07 AM   #126
gabedude
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Quote:
Originally Posted by newblue View Post
For everyone who did this with top feed and needed an adapter, how did you route the line from the adapter to the rail? I have an gimmick silicone inlet and It seems to route the injection hose I will have to have a very long hose go above the inlet to the line so that it doesnt kink. Anyone have some insight on this? Will the extended hose be a problem?
Over the top of the intake manifold. I zip tied it to stay in place with proper hood clearance. I have rails now and run a long line to the distro block and relocated FPR (on top of the dogbone) for the air pressure line (which stock is right next to the fpr on the rail). It seems like a long line to reference 1:1 rising rate fuel pressure, but it works just fine. Also, the return line is rather long from the FPR because it has to take a U turn over the turbo. Still, it works just fine.
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Old 09-03-2011, 03:00 PM   #127
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Perfect, appreciate the feedback gabe!
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Old 03-30-2012, 10:28 PM   #128
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Im doing this now, but converting to top feeds and topfeed tgv's in the process, stock wrx rails, sti fpr.

A note, make sure the total length, ie metal line on fuel rail and soft fuel line, is the same for feed and feed on both sides and return an ld return on both sides, 02 wrx rails the passenger rail has a significant ammount of extra metal fuel line to run through than any of the others. Ill take measurments when im done for an easy diy
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Old 04-16-2012, 11:48 AM   #129
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Thank you very much for the detailed pics and your work. It's much appreciated!
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Old 05-08-2012, 06:13 PM   #130
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bump! any update for how the fpr is done and connected for a WRX?
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Old 10-03-2012, 03:06 PM   #131
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bump for my own reference :P
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Old 11-16-2012, 10:16 PM   #132
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What size line is on the fpr. It's never mentioned and I doubt the stock one is long enough?
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Old 07-12-2013, 06:27 PM   #133
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After much reading I'm still confused so maybe an Internet engineer can explain this to me. As far as fuel lines to/from the rail (parallel setup), I have read that some believe that they need to be equal length. It seems that the fpr will create the same amount of pressure for each return line regardless of length so long as the line doesn't run dry, but in that case the motor would be well past blown up. Someone drop some knowledge.

Edit: I realize there will be no hard data unless someone has a 4 wideband setup but hopefully someone knows a sound and proven engineering theory that would apply.

Last edited by Ishart; 07-12-2013 at 06:35 PM.
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Old 10-07-2015, 02:54 PM   #134
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Quote:
Originally Posted by DuckStu View Post
*And roughly 7 feet of 5/16" fuel injection hose. (About $1.29 a foot, or $9.00)
I just want to point out, there is no way you got 5/16" fuel INJECTION hose for 1.29 a foot. Maybe transfer hose, good to about 50-80 psi depending on quality, but not high pressure injection hose.


anyways, doing this today on my 08 sti, should be interesting with the routing...
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Old 10-19-2017, 08:17 AM   #135
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I Hate Photobucket!!!!
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Old 10-20-2017, 12:16 AM   #136
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No kidding. They've made it pretty hard to repair the busted images, too. I have a few dozen pics in threads elsewhere and I've tried to download my images so I can host them elsewhere but their site is always slow or broken.

I even get the "upgrade your account to enable third-party hosting" fail images when I try to view my pics on THEIR web site, which is just ****ing asinine.
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Old 11-03-2017, 02:28 PM   #137
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Update your photos..
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Old 01-10-2018, 02:11 AM   #138
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so i will be attempting this on my 2008 wrx as i already have my manifold off for other reason, figured it cant hurt for a pretty low $$ investment.
I figure going parallel will be very beneficial as i run e85 a lot, but i do not want to fork over the money for fuel rails.

My question to you guys is, will running my lines this way cause any issues, i plan to use the stock solid lines and run a small amount of FI hose to make the setup parallel.

In the following pics, red is 5/16 FI hose, black are hard OEM lines, and yellow are the tees i plan to use.

here is the car stock series fuel routing


and here is my plan, as simple as i could think to make it, and i have the room for the extra FI hose under the intake manifold as well as routing it out to the tee after the filter directly between the plenum as the stock lines run, will also keep stock FPR.



i am not too familiar with how flow works, so does using a tee where the return lines meet create an issue with pulsation, should a dampener be added, or is this setup ok to run?

I plan to use these tees as they are the smallest i could find, the barbs are 5/16".
Also just cause it was brought up a few years back, 5/16" e85 compatible FI hose is running me $4.44/ft.

Last edited by rubmetoasty; 01-10-2018 at 02:35 AM.
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Old 01-10-2018, 07:05 AM   #139
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That's pretty close to how I ran mine. I kept the stock dampers in place and tee'd the lines under the manifold just keep them all equal length as possible. I might recommend flaring or scuffing up the ends of the hard line to keep the hose line from leaking. Over all it worked great for a few years for me until I needed to buy fuel rails anyways.
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Old 01-10-2018, 12:29 PM   #140
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Originally Posted by TyranosaurusWRX View Post
That's pretty close to how I ran mine. I kept the stock dampers in place and tee'd the lines under the manifold just keep them all equal length as possible. I might recommend flaring or scuffing up the ends of the hard line to keep the hose line from leaking. Over all it worked great for a few years for me until I needed to buy fuel rails anyways.
sweet thanks for the reply, i have the car at about 320 hp to the wheels and only plan to get to about 350max on a dyno, so i should be more then ok on the stock rails.

I was actually planning on flaring out every hard line end i plan to use just in case, thx for the heads up.
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Old 01-10-2018, 03:08 PM   #141
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Quote:
Originally Posted by rubmetoasty View Post
i am not too familiar with how flow works, so does using a tee where the return lines meet create an issue with pulsation, should a dampener be added, or is this setup ok to run?
Your mass flow is choked by the diameter of the single supply diameter (i.e. the smallest orifice in the entire system).

The only time parallel lines are necessary (or even beneficial) would be if the rails themselves caused a choke point in the system (i.e. rails are drilled to -6AN dia. and you want to run -8AN supply and return lines).

I think a quick search on Google will reveal two things:

- 75% or better of the parallel vs. series stuff grew out of the Subaru community.
- 99% or better of the discussions on this topic (Subaru or otherwise) are all people throwing random theories out about pressure drop at the 'end of the rail'. Fluid systems *can* get complex... but we really don't need to get complex to see how parallel lines don't help you.

(Let's come back to the issue of damping the system in a second, because this *is* a Subaru specific thing due to the placement of the filter and the later 2008+ system)

Given an adequate rail diameter, explain to me why the last injector in the series would receive a lower pressure than the first one with these two details in mind:

1. You aren't running batch injection - all modern fuel injection systems have injectors firing in-order, one-by-one.
2. Your fuel pressure regulator is the last thing in the system and works with the pump to increase or decrease demand based on need.

You will have frictional losses in pressure between the first injector and last injector, yes - but when the entire system friction loss is approximately 2-5 psi along the whole 15-20 ft. length from TANK to REGULATOR... how much do you really think you're losing in 12 in. or so of plumbing?

A few other reasons you might not want parallel lines:

- Greatly increased chance of leaks due to many, many more connection points.
- If one line experiences a restriction, the other line will flow more; (path of least resistance).
- Added cost without added benefit.

All that in mind, I'd ask yourself if you need to run larger lines than the diameter of your fuel rails. If the answer is no, we can move on to the issue of fuel damping.

Why does the USDM 04-07 WRX/STI (and all market 2008+ models) have fuel damping concerns?

Because US requirements forced the filter from it's original location (on the LH strut tower) to the fuel tank and added dampers to the lines near the regulator and rails as a 'quick fix'. This applies to 04-07 models which didn't really see much of a problem. Moving the filter from the tank to the original location still provides damping effects and simplifies the system greatly.

In 2008+ models, Subaru decided to let owners beta-test their fuel system that bypassed fuel in a different way (bypassed fuel was split between tank return and supply line - as a simplified explanation... basically Subaru tried to supply fuel to the rails in two directions). Why anyone would run parallel lines to fix this rather than just return the system to a simpler state is beyond me. Using a simple manifold referenced regulator is easy enough to do and I know of at least one manufacturer that makes a plug-and-play kit that requires only minor tuning housekeeping afterwards.

Last edited by mrsaturn7085; 01-10-2018 at 03:18 PM.
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Old 01-10-2018, 07:24 PM   #142
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Quote:
Originally Posted by mrsaturn7085 View Post
Your mass flow is choked by the diameter of the single supply diameter (i.e. the smallest orifice in the entire system).

The only time parallel lines are necessary (or even beneficial) would be if the rails themselves caused a choke point in the system (i.e. rails are drilled to -6AN dia. and you want to run -8AN supply and return lines).

I think a quick search on Google will reveal two things:

- 75% or better of the parallel vs. series stuff grew out of the Subaru community.
- 99% or better of the discussions on this topic (Subaru or otherwise) are all people throwing random theories out about pressure drop at the 'end of the rail'. Fluid systems *can* get complex... but we really don't need to get complex to see how parallel lines don't help you.

(Let's come back to the issue of damping the system in a second, because this *is* a Subaru specific thing due to the placement of the filter and the later 2008+ system)

Given an adequate rail diameter, explain to me why the last injector in the series would receive a lower pressure than the first one with these two details in mind:

1. You aren't running batch injection - all modern fuel injection systems have injectors firing in-order, one-by-one.
2. Your fuel pressure regulator is the last thing in the system and works with the pump to increase or decrease demand based on need.

You will have frictional losses in pressure between the first injector and last injector, yes - but when the entire system friction loss is approximately 2-5 psi along the whole 15-20 ft. length from TANK to REGULATOR... how much do you really think you're losing in 12 in. or so of plumbing?

A few other reasons you might not want parallel lines:

- Greatly increased chance of leaks due to many, many more connection points.
- If one line experiences a restriction, the other line will flow more; (path of least resistance).
- Added cost without added benefit.

All that in mind, I'd ask yourself if you need to run larger lines than the diameter of your fuel rails. If the answer is no, we can move on to the issue of fuel damping.

Why does the USDM 04-07 WRX/STI (and all market 2008+ models) have fuel damping concerns?

Because US requirements forced the filter from it's original location (on the LH strut tower) to the fuel tank and added dampers to the lines near the regulator and rails as a 'quick fix'. This applies to 04-07 models which didn't really see much of a problem. Moving the filter from the tank to the original location still provides damping effects and simplifies the system greatly.

In 2008+ models, Subaru decided to let owners beta-test their fuel system that bypassed fuel in a different way (bypassed fuel was split between tank return and supply line - as a simplified explanation... basically Subaru tried to supply fuel to the rails in two directions). Why anyone would run parallel lines to fix this rather than just return the system to a simpler state is beyond me. Using a simple manifold referenced regulator is easy enough to do and I know of at least one manufacturer that makes a plug-and-play kit that requires only minor tuning housekeeping afterwards.
Really thank you for taking the time to explain that.
I do a lot of research before i attempt any kind of project like this, and this was one i only decided on because i have the manifold off, and like you just mentioned, i was going off forum posts stating that "someone did some testing and found pressure fluctuation at the end of the second rail in the series. My thought process was elementary, i am an aerospace welder, and in my head running parallel made sense, but i did not consider that the injectors never fire in a batch, but as you stated, one by one.

At this point i have not run the lines yet as im still waiting on a few new vacuum lines to replace while i have everything off, but your post is making me double think whether it is worth it. I know at my power levels fueling should not be an issue on the stock setup, with a aeromotive 340 stealth pump and removed stock fuel filter, running 10 micron Golan under the hood.
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Old 01-10-2018, 09:02 PM   #143
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also for anyone else that runs into this, i originally did not find the following thread when searching around on my phone, but Maxwell Power explains even better why going parallel on these engines is not ideal.

I will definately be keeping my fuel lines stock, just replacing the old brittle hoses with new line i bought for this project.

https://forums.nasioc.com/forums/sho...2162858&page=2
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Old 01-11-2018, 05:38 PM   #144
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This sums it up.

Quote:
Originally Posted by Maxwell Power View Post
Pressure differential is moot and frankly I'm surprised anyone thinks it exists.

Here's why:

1. From the first injector to the last, the amount of fuel being used is less and less in steps. So from the beginning, you have less flow which lowers any potential for pressure drop. The largest demand on the fuel system is the line in the frame rail. Once it hits the first injector, the demand is less, which means flow rate is less, which means pressure drop is less.
2. The fuel system does not flow ONE flow rate through the whole system evenly.
3. The fuel pressure regulator is at the end. So if it sees a drop in fuel pressure at the last injector, it's going to bypass LESS fuel, which therefor keeps the pressure more balanced from beginning to end.


Lastly:
Nobody has ever had misfire issues from Series lines.
Many people have had misfire issues with Parallel lines.
Nobody has been able to prove any benefit with Parallel.
Many people have experienced uneven fueling from cylinder to cylinder with parallel.
The first year subaru implemented parallel rails, TONS of misfire issues. Just look up any 08+ STi.

Parallel fuel rails result in large differences in rail temperature and fuel temperature. Fuel temperature is a very important part of fueling (how important? 50C is over 6% fueling. 6% is a lot when we're concerned over 1 or 2% see the last article http://www.injectordynamics.com/NewsletterFeb2013.html). Someone mentioned that by going parallel you lower the speed of the fuel in the rail by half. This is true, in fact in extreme cases it's more than half. HOWEVER, that's not ideal. You want the highest velocity you can get away with without creating a back pressure and pressure drops. Higher velocity means you do a better job of balancing rail temps. Balanced rail temps means balanced fueling. Nice fat rails with a large quantity of fuel going through them would be nice too, but too big and fuel have such a slow fuel flow that you'd once again establish large changes in fuel temp from rail to rail.

So what you guys are doing is creating a problem while trying to prevent a problem that doesn't exist.

If you go series with injectors in the wrong order, you could have issues. However, our firing order is linear down the fuel rail. Subaru H4 is the only engine ever created to do this. The order of fuel feed should be opposite of engine firing order. This means that the fuel injectors are always firing towards the source of fuel. That means that you aren't going to get any lack of fuel from the load on the rail.

In V8's, I4, I6 etc, the firing order is not in a linear fashion down the rail and it is absolutely important and correct to go parallel with your fueling. Subaru isn't like any other engine out there.


Any lack of fuel is from a pump that is too small or from a rail system that is too small to handle the flow rate. It isn't from being series.
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