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Old 04-10-2011, 12:54 AM   #26
dorian291
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Default hope this helps

will send pics, as soon as I get time.
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Old 05-25-2011, 09:56 AM   #27
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lets say keeping the stock lines from trunk to engine bay...

600Lph pump, just adding aftermarket RAILS and keep engine bay to engine STOCK with the stock in line system, what will be the loss???

or adding the FULL FUEL RAIL SYSTEM, kepping trunk to engine bay stock, adding aftermarket parallel fuel lines to rails, all after market... the loss will be?
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Old 05-25-2011, 10:57 AM   #28
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Quote:
Originally Posted by xandi911 View Post
600Lph pump, just adding aftermarket RAILS and keep engine bay to engine STOCK with the stock in line system, what will be the loss???
You can't do that, the stock lines will not attach to aftermarket rails. With aftermarket rails, you must use aftermarket lines in the engine bay, otherwise you will never be able to connect it together.

Quote:
Originally Posted by xandi911 View Post
or adding the FULL FUEL RAIL SYSTEM, kepping trunk to engine bay stock, adding aftermarket parallel fuel lines to rails, all after market... the loss will be?
That's why I made this:

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Originally Posted by the suicidal eggroll View Post
With the recent trend of series/parallel rail discussions and the new batch of high flow drop-in pumps available (and with everybody wanting to get the highest flowing pump available, regardless of what they actually need), I decided to add the equations for calculating pressure loss through the fuel lines, including the pressure drop between the first and last injector given line size, rail setup, etc. to my turbo/fuel calculator.

http://forums.nasioc.com/forums/show....php?t=2158062

(tab 4)

It's currently set up for a stock line/rail config on a single Walbro 255, so you can adjust as necessary, see the effect of going to a Bosch 044, DW300, or dual Walbro 255 on the stock lines, etc.

There are references at the bottom of the table to give you the values for the density and viscosity of gasoline and E85, and example line roughness values for stock lines (grossly approximated, though it doesn't make a huge difference) and aftermarket teflon lines.
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Old 05-25-2011, 11:37 AM   #29
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I do know that Maxwell Power will not sell you a parallel kit. They told me that the will not run parallel on their cars. And they won't sell anything that they would not run on their own cars.

I think that says lots for series set-ups.
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Old 05-25-2011, 11:54 AM   #30
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Originally Posted by 03WRXWagon View Post
I do know that Maxwell Power will not sell you a parallel kit. They told me that the will not run parallel on their cars. And they won't sell anything that they would not run on their own cars.

I think that says lots for series set-ups.
so you are telling me ,even flowing 600lph at E100, Maxwell Power will keep STOCK SERIES LINES AND STOCK RAILS???

and what about the LOSS SUICIDAL EXPLAINED US?


d@mn im confused...
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Old 05-25-2011, 12:00 PM   #31
the suicidal eggroll
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Originally Posted by xandi911 View Post
so you are telling me ,even flowing 600lph at E100, Maxwell Power will keep STOCK SERIES LINES AND STOCK RAILS???

and what about the LOSS SUICIDAL EXPLAINED US?


d@mn im confused...
They don't keep it stock, they keep it in series. You can still plumb aftermarket rails and aftermarket lines in series instead of parallel. You'll need to go with larger lines to keep the pressure drop low though, and you'll still never get the pressure differential as low as with a parallel setup.
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Old 05-25-2011, 12:15 PM   #32
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They don't keep it stock, they keep it in series. You can still plumb aftermarket rails and aftermarket lines in series instead of parallel. You'll need to go with larger lines to keep the pressure drop low though, and you'll still never get the pressure differential as low as with a parallel setup.
MMM just understood! and what should be the best after market kit, with the lines and rails BOLT ON??

any experience with after market KITS? perrin, agency power... i dont wanna change FPR now.. my stock one my handle...
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Old 05-25-2011, 02:58 PM   #33
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Quote:
Originally Posted by xandi911 View Post
so you are telling me ,even flowing 600lph at E100, Maxwell Power will keep STOCK SERIES LINES AND STOCK RAILS???

and what about the LOSS SUICIDAL EXPLAINED US?


d@mn im confused...

I have no idea about the pressure drop. Suicidal knows way, way more about this stuff than I do and is a better resource.

Just stating what I was told by a very reputable engine builder/tuner. It is not to say that parallel won't work or even has less pressure drop. I was hoping that maybe they (maxwell power) would chime in.
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Old 10-17-2013, 06:04 PM   #34
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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.

Last edited by Maxwell Power; 10-17-2013 at 06:10 PM.
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Old 10-27-2013, 05:29 PM   #35
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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.
Interesting points and what you have stated does make sense. I may just try a series setup this time around since my car is all apart right now anyways, my previous setup was parallel with equal length lines (all 6an) from the y splitter to the rails on the feed size and also equal length lines from the rails going to each side of my Weldon FPR directly, instead of joining the lines again and running a single line to the FPR. I assume this would be the best way to do parallel setup since a nice Aeromotive Y block would keep velocity up better then a T splitter and keeping both lines from each rail exactly equal and also each side ran back to FPR separately.

One other way I think you could possibly better this parallell setup would be to run a bigger volume, lets say 8an, feed line directly off the fuel pump hanger then use a 8an to 6an nice Aeromotive Y block in the engine bay, which (I think) would come close to matching the fuel velocity on both 6an split feed lines now going to the rails with the main velocity on the bigger volume 8an main feed line, which would then also keep the main line fuel temperature pretty much the same temperature as the fuel going to rails even after being split by the Y block. Does this theory seem correct?

I could be completely wrong as I have not done any real testing and im defiantly not an engineer lol. Either way this is an interesting subject to discuss and I think the main problems people report after doing parallel setup is caused by a half-assed setup. Seems like its much easier for the average person to screw up putting together proper parallel setup and just end up making matters worst like you said.
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Old 10-27-2013, 06:14 PM   #36
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I have a friend here who has a 04 wrx wagon stock 2.0 stock engine with an upgraded intake, downpipe and 3 inch exhaust coupled with a custom tune done by him. The maf is the stock used one. Everything else is stock.

He had bought a set of perrin equal length parallel fuel rails and lines and wants to put them on his engine. After reading this thread and the info that Dom shared which I understand the basic concept of, I believe that my friend had wasted his money in a round about way.

He is putting out probably around 255 hp maybe? At this point, would the stock lines and rails still be fine, or can he upgrade his lines but keep the rails?
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Old 10-27-2013, 11:14 PM   #37
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He in no way needs any fuel system upgrades for that power level.
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Old 10-29-2013, 02:39 PM   #38
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Stock rails are good to 500whp.
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Old 10-29-2013, 02:54 PM   #39
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Stock rails are good to 500whp.
I believe stock rails are good to 500hp but from reading, aftermarket rails get rid of the infamous stumble on the GR. I tried just about everything other then rails. That being said......rails going in this week.
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Old 10-29-2013, 03:33 PM   #40
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My understanding is the stumble can be tuned out adjusting the fueling compensation tables. Also reroute how the hoses run to and from the stock rails. Another is a older style sti, or aftermarket fuel pressure regulator.
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Old 10-29-2013, 04:09 PM   #41
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My understanding is the stumble can be tuned out adjusting the fueling compensation tables. Also reroute how the hoses run to and from the stock rails. Another is a older style sti, or aftermarket fuel pressure regulator.
Well tuning it out couldn't be done. I tried the 3' fuel line mod, ams fpr kit, and the Lucas. The Lucas has been by far the best. The other two didn't do ****. Ams fpr kit came w a fuelab aftermarket fpr. Didn't work. The true solution is rails. I been talking w NOMORESHANKS. he did rails and boom! It was gone
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Old 10-29-2013, 06:05 PM   #42
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I believe stock rails are good to 500hp but from reading, aftermarket rails get rid of the infamous stumble on the GR. I tried just about everything other then rails. That being said......rails going in this week.
That's great. However, I was talking to the other guy about his 255hp car with upgraded fuel rails.
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Old 10-30-2013, 12:14 AM   #43
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Originally Posted by Maxwell Power View Post
That's great. However, I was talking to the other guy about his 255hp car with upgraded fuel rails.
I knew that you were

So, basically I need to tell him to sell his kit that he bought... I'll try though.. lol

Last edited by subi400; 10-30-2013 at 12:20 AM.
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Old 10-30-2013, 12:16 AM   #44
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I see no advantage at all. I've taken apart engines running over 500whp for years on all stock lines and had no differences in anything on any cylinder. I just don't see what kind of advantage you think you'd get... if it isn't a restriction or limitation in any way, what can you possibly gain?
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Old 10-30-2013, 03:48 AM   #45
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I see no advantage at all. I've taken apart engines running over 500whp for years on all stock lines and had no differences in anything on any cylinder. I just don't see what kind of advantage you think you'd get... if it isn't a restriction or limitation in any way, what can you possibly gain?
There isn't any gain once the whole system is recognized as being sufficient up to the 500 whp mark as you stated. I'll talk to my friend more about this and see what happens.

Thanks
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Old 10-30-2013, 12:28 PM   #46
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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.
Just out of curiosity, does the same apply to the Subaru H6 in your opinion? With a firing order of 1-6-3-2-5-4
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Old 10-30-2013, 01:47 PM   #47
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I just want to say thank you to maxwell power for chiming in on this and dropping some serious knowledge that honestly everyone should know.
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Old 10-31-2013, 05:21 AM   #48
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Id rather run the proper sized lines to keep pressure drop to a minimum, it will allow your whole fuel system to run more consistent and efficient, especially when using an intank pump because they drop off in flow significantly as the pressure demand goes up.

Notice how some people can magically make ~50whp more before "running out of injector" on the same size injectors,fuel, and pump? Sure there could be alot of other factors involved but pressure drop from total line size could be a big part.
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Old 10-31-2013, 04:23 PM   #49
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Originally Posted by dragoontwo View Post

Just out of curiosity, does the same apply to the Subaru H6 in your opinion? With a firing order of 1-6-3-2-5-4
No. It does not. Parallel would be appropriate, but every step should be taken to maximize flow though the rails evenly and quickly to help control temperature.
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Old 10-31-2013, 04:26 PM   #50
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Originally Posted by NA STI View Post
Id rather run the proper sized lines to keep pressure drop to a minimum, it will allow your whole fuel system to run more consistent and efficient, especially when using an intank pump because they drop off in flow significantly as the pressure demand goes up.

Notice how some people can magically make ~50whp more before "running out of injector" on the same size injectors,fuel, and pump? Sure there could be alot of other factors involved but pressure drop from total line size could be a big part.
The only difference I see is when comparing before and after 08. The fuel pump hanger design in the new cars impedes flow and results in less overhead
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