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Old 08-26-2005, 11:55 AM   #1
suby53
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Default fuel system mod?

I have a tdo4 on my 1.8 impreza and was reading about a fuel system mod on northursalia.com ( series to parallel ). Has anyone tried this with aftermarket forced induction? if so, how did it work out for you? Worth it?

[url=http://www.northursalia.com/modifications/drivetrain/fuelrail/fuelrail.html]
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Old 08-26-2005, 08:07 PM   #2
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I am going to give the same answer i give everyone. This mod is BS.
-Jake
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Old 08-26-2005, 10:52 PM   #3
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Agreed.
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Old 08-26-2005, 11:02 PM   #4
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i had a td04 on the 1.8, but i switched to turbo legacy rail and injectors. But this required an safc to control as i felt. Unless you plan to get a better rising rate fuel pressure regulator, doing a parallel will not raise your fuel pressure through the regulator... correct me if error
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Old 08-27-2005, 10:36 AM   #5
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I believe the mod is just to try and balance the fuel delivery to all the cylinders. It has nothing to do with increasing fuel pressures, in fact, I believe that it may lower the fuel line pressures, if only a little bit and a for short period of time.
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Old 08-28-2005, 02:00 PM   #6
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NO NO NO NO, and NO.

The mod is meant to to distribute fuel evenly to all 4 injectors. The thought was that the injectors are fed inline, so the 4th injector doesnt recieve enough fuel because the other 3 are somehow using the fuel pressure before it gets to the last one. The parallel fuel rail mod, would run the fuel parallel instead of inline, thus fuel pressure would be even to all injectors. However, this idea is fundamentally flawed.


___________________________________
Consider this:

A garden hose. The faucet is turned on, and the nozzle at the end is shut off. There is pressure in the hose that is not moving, correct?

Now, Poke 4 holes in the hose. Water starts spraying out, assuming the 4 holes are the same size, equal amounts of water will flow from each one, no matter how far away from the faucet the hole is.

If pressure in the hose drops, it will drop evenly to each hole.
___________________________________

This principle is the same in the fuel system, therefor the is no problem with the 4th injector being starve, this is a myth. Im amazed at how many people CONTINUE TO FALL FOR THIS.

-Jake

I really think a moderator should sticky this.
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Old 08-28-2005, 02:22 PM   #7
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also there should be no point in getting fuel rails too
people get them thinking theyre going to do miracles
truth is though if youre feeding a 1" dia. hole with fuel through a .25" dia line...youre only gonna get .25" of flow
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Old 08-28-2005, 06:46 PM   #8
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Quote:
Originally Posted by White 2.5rs
also there should be no point in getting fuel rails too
people get them thinking theyre going to do miracles
truth is though if youre feeding a 1" dia. hole with fuel through a .25" dia line...youre only gonna get .25" of flow
w3rd!
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Old 08-29-2005, 08:41 AM   #9
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Thanks for all your help guys. I had the turbo legacy injectors and fuel rails on my last set up. It was worlds better than this set up with the blox fmu and stock injectors an the same 9 psi.
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Old 08-29-2005, 02:36 PM   #10
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Not to mention the potential danger of rubber lines on top of a hot block- there's a reason the factory ones are metal. It is more likely the intake manifold design or the design of the coolant passages that causes the $4 to run hotter.
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Old 08-29-2005, 02:41 PM   #11
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a little side track again but what about the rumors of disconnecting the hose that connects to your egr port on the intake manifold? Has anyone actually gotten lower temperature results on their aftermarket system?
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Old 08-30-2005, 10:00 AM   #12
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Quote:
Originally Posted by Unsung Boxer
Consider this:

A garden hose. The faucet is turned on, and the nozzle at the end is shut off. There is pressure in the hose that is not moving, correct?

Now, Poke 4 holes in the hose. Water starts spraying out, assuming the 4 holes are the same size, equal amounts of water will flow from each one, no matter how far away from the faucet the hole is.

If pressure in the hose drops, it will drop evenly to each hole.
___________________________________

This principle is the same in the fuel system, therefor the is no problem with the 4th injector being starve, this is a myth. Im amazed at how many people CONTINUE TO FALL FOR THIS.

-Jake
OK. So, let me ask this. And this is nothing more than a question.

I understand your analogy but, why then are there apparently so many people having the 3rd and/or 4th piston burnt, supposedly due to a starved piston, supposedly due to the failure of the stock Suabru fuel rails to properly supply fuel to all 4 cylinders.

Presuming that the fuel rail/starved piston is nothing more than a myth, the issue of the burnt piston supposedly lends credence to the fact that it is not a myth.

Couldn't there be something is the way the fuel flows through the rails, something to due to the internal rail design, that causes some type of restriction? I've never cut open the fuel rail.
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Old 08-30-2005, 01:11 PM   #13
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Quote:
Originally Posted by Samurai Jack
OK. So, let me ask this. And this is nothing more than a question.

I understand your analogy but, why then are there apparently so many people having the 3rd and/or 4th piston burnt, supposedly due to a starved piston, supposedly due to the failure of the stock Suabru fuel rails to properly supply fuel to all 4 cylinders.

Presuming that the fuel rail/starved piston is nothing more than a myth, the issue of the burnt piston supposedly lends credence to the fact that it is not a myth.

Couldn't there be something is the way the fuel flows through the rails, something to due to the internal rail design, that causes some type of restriction? I've never cut open the fuel rail.
First of all, im a Subaru Technician, and I really dont know where this "common knowledge" that 3rd and 4th pistons become burnt often.
EJ25 engines do have have a problem w/ #4 cylinder going out of round, and causing piston slap primarily due to its skirtless pistons. Yet, that is the only trend Ive really noticed. I think someone got their facts crossed somewhere along the way.

Furthermore, the fuel rails seem to have a solid design, If this was a real problem, dont you think that Subaru would have re-engineered them for such a simple fix?

Lastly, no one has shown any of this evidence:
1. The injectors flow unevenly.
2. The Rails are the culprit
3. The Fuel Rail mod causes the injectors to flow evenly.

Neither the problem, the action, or the solution can be verified, so until proven otherwise, this is all just Theory, and a pretty BS one at that!.

-Jake
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Old 08-30-2005, 07:18 PM   #14
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someone needs to steal the CAD file for the intake manifold..put it in Flow Works...and see what happens
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Old 08-30-2005, 07:37 PM   #15
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Unsung Boxer
First of all, im a Subaru Technician, and I really dont know where this "common knowledge" that 3rd and 4th pistons become burnt often.

I don't either. But, from time to time there are threads here, and on other WRX forms, that the issue of a burnt 3rd and/or 4th piston has happened. From there, the issue turns into one of the starved piston thing. And then, there is some poll on here about the number of WRX people who have had a burnt piston, w/ the #4 piston being the largest number.

Unsung Boxer:
EJ25 engines do have have a problem w/ #4 cylinder going out of round, and causing piston slap primarily due to its skirtless pistons. Yet, that is the only trend Ive really noticed. I think someone got their facts crossed somewhere along the way.

Could be where it started from.

Unsung Boxer:
Furthermore, the fuel rails seem to have a solid design, If this was a real problem, dont you think that Subaru would have re-engineered them for such a simple fix?

One would think so, unless it only shows up under specific circumstances, which are hard to repeat. Of the 10s of thousands of WRXs/STis Subaru sells, it may be such a small thing that it doesn't seem worth the effort, if it's true.

Unsung Boxer:
Lastly, no one has shown any of this evidence:
1. The injectors flow unevenly.
2. The Rails are the culprit
3. The Fuel Rail mod causes the injectors to flow evenly.

Well, I would throw out #1 and stick w/2 & 3 since the issue is directed at the rails.

Unsung Boxer:
Neither the problem, the action, or the solution can be verified, so until
proven otherwise, this is all just Theory

And you can't argue with that
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Old 08-30-2005, 07:57 PM   #16
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intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold intake manifold
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Old 08-30-2005, 08:45 PM   #17
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Good thing I never went through with this mod - I was thinking about it but it was quite involved plus I would be having the shop doing this work and they had no experience other than what was documented. I guess as long as I have good fuel pressure and no clogged injectors I should be fine
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Old 08-30-2005, 10:28 PM   #18
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Quote:
Originally Posted by Samurai Jack
Unsung Boxer:
Lastly, no one has shown any of this evidence:
1. The injectors flow unevenly.
2. The Rails are the culprit
3. The Fuel Rail mod causes the injectors to flow evenly.

Well, I would throw out #1 and stick w/2 & 3 since the issue is directed at the rails.
LOL.

If the fuel rails dropped in pressure the injectors would flow unevenly as a result of it...

/boggle
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Old 08-31-2005, 10:40 AM   #19
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Perhaps, but not according to Unsung Boxer's analogy, which I am taking at face value for the purpose of the discussion.

Quote:
Consider this:

A garden hose. The faucet is turned on, and the nozzle at the end is shut off. There is pressure in the hose that is not moving, correct?

Now, Poke 4 holes in the hose. Water starts spraying out, assuming the 4 holes are the same size, equal amounts of water will flow from each one, no matter how far away from the faucet the hole is.

If pressure in the hose drops, it will drop evenly to each hole.
Which brings it back to the fuel rails, which is the subject being discussed.

Or, maybe the intake, right White 2.5rs?
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Old 08-31-2005, 11:44 AM   #20
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has anyone disconnected their egr port hose from the intake manifold, capped it (aftermarket turbo car) and noticed results?
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Old 08-31-2005, 01:16 PM   #21
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Playing Devil's Advocate.

Using stock fuel pump and regulator. After market turbo on a normally aspirated engine.

As we all know, when you increase boost you must also increase fuel. This is done by increasing the duty cycle of the injectors.

Imagine a river that flows at a constant rate, with four gated channels off of it's left side. Normally, the gates are open a modest amount. As more water is needed in each channel (under boost)the gates are opened farther and farther (duty cycle). Eventually the open gates will have more demand than the river can keep up with and the river will start to dry up before it gets to the fourth channel. Hence it starts to starve for water.

The purpose of this mod is to put one channel on the left and one directly across from it on the right. With another set of channels down stream. If the demand on the river starts getting too great the second set might start getting less water BUT they're sharing the loss equally. The fourth channel comes out ahead.

I don't even begin to have a clue if you can boost to the point of leaning out the #3 cylinder using the stock fuel pump and regulator.

However, as with any mod, you have to mod everything. Many people just slap on a turbo and call it good. By putting in a high flow fuel pump and a rising rate regulator you increase the ability of the fuel system to keep up with the demand. In other words, you give the river the ability to increase it's flow as the four channels demand more water.

I don't see a need for this mod if you upgrade your fuel system along with the turbo. On the other hand, I don't see how it can hurt other then it's work that probably doesn't need to be done and the very good point made earlier in this thread about rubber hoses on a hot block.

For what it's worth, my two cents.

Resbum
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Old 08-31-2005, 03:08 PM   #22
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rrfpr/fpr solves lack of flw probs assuming the pump can keep up
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Old 08-31-2005, 09:28 PM   #23
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Quote:
Originally Posted by Resbum
Playing Devil's Advocate.
For WIW, I like the Devil's Advocate approach
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Old 08-31-2005, 10:23 PM   #24
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Quote:
Originally Posted by Resbum
Playing Devil's Advocate.

-snip-

For what it's worth, my two cents.

Resbum
Ah, but doesn't your river analogy involve a system with flow, but virtually no pressure (at least at the surface)? For something like this to happen in the fuel rail, fuel pressure would first have to drop essentially to zero. I can't recall seeing any threads where someone with an adequately-large fuel pump managed to pull down their pressure enough to burn a piston.

...just playing Devil's Advocate to your Devil's Advocate.

FWIW, I DID do the fuel rail mod. I really doubt I'll do it again if I work on another manifold.

_Jeff
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Old 09-01-2005, 02:23 AM   #25
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Thanks Portly,

The river analogy was just an attempt to explain the purpose and thinking behind this mod.

At the end of my post I stated that if you put in a larger fuel pump and rising rate regulator with the turbo, this mod wasn't needed.

A point my river analogy and the garden hose analogy didn't take into account is that only one of the gates/holes will ever be open at a time. Just like the injectors on your engine. That throws a whole new twist on the subject.

Resbum

PS - I bought my 99RS with this mod already done on it.
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