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Discussion Starter #1
Whats up yall. Im really torn if i should do the iag/cobb rails and pre made lines along with cobb V2 inlet before i retune for E85, or am i totally fine with the stock rails/lines for now? I am not upgrading the turbo anytime soon. Also, if i would get premade fuel lines, should i be getting the iAG or cobb? the iAG comes with the adjustable aeromotive 1000 FPR which future proofs the build, while if i go with cobb, i can retain the cobb fuel pressure regulator since im using the base fuel pressure anyway. I daily the car and usual canyon runs(not all the time). need opinions if im wasting money on the rails/lines.

Cobb Intake With Box
Cobb 1050x Injectors
Cobb Aem 340 F.Pump
Cobb Fuel Pressure Regulator
Cobb Fuel Pressure Sensor
Cobb EBCS
Grimmspeed Catted Downpipe
Grimmspeed V2 Heatshield
Cobb Air Oil Seperator
4th cylinder cooling mod
ETS Quiet Exhaust
Iwire Xseries Stealth Wideband
Protuned by Josh Dank @danktuned
 

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no reason to upgrade lines or rails for stock turbo E85

I run stock lines/rails and am running a bigger turbo and ID1300s with no issues.
 

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Discussion Starter #3
no reason to upgrade lines or rails for stock turbo E85

I run stock lines/rails and am running a bigger turbo and ID1300s with no issues.
Thanks for the reply! i am getting carried away with people saying i gotta get the rails and lines for equal distribution of fueling for e85
 

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Thanks for the reply! i am getting carried away with people saying i gotta get the rails and lines for equal distribution of fueling for e85
Obviously discuss with your tuner, but when I asked this same question to my tuner(who is on here, Yamahasho) he told me there was no need for it.
 

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The big thing at your point in the build is whether you get the dreaded stumble. The stumble is caused by the unequal length of lines, and the reverberation of the injector pulses causing waves of slightly lean conditions. In stock form your fuel lines have pressure dampeners, and for the size of the injectors and fuel flow it covers it. It MAY become known with larger injectors. I know before I went equal length fuel lines that I did solve it by putting 3 feet of additional fuel line in the engine bay( But I obviously it is a patch type fix as I don't think you like having any more fuel/ lines in the engine bay than what is needed.
 

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Discussion Starter #6
The big thing at your point in the build is whether you get the dreaded stumble. The stumble is caused by the unequal length of lines, and the reverberation of the injector pulses causing waves of slightly lean conditions. In stock form your fuel lines have pressure dampeners, and for the size of the injectors and fuel flow it covers it. It MAY become known with larger injectors. I know before I went equal length fuel lines that I did solve it by putting 3 feet of additional fuel line in the engine bay( But I obviously it is a patch type fix as I don't think you like having any more fuel/ lines in the engine bay than what is needed.
Hey! thanks for the reply! hmm , im looking at the cobb fuel rails and lines and it does look like they split it in 2 Y blocks, therefore equal length lines along with the “oem” cobb pressure regulator and they have said that this is the only kit that really takes out the “stumble” getting their cobb fuel pressure regulator by itself, only band aids the “stumble”. Also on the other hand, the iag ptfe rails and lines kit(premade) are ran differently? are you also recommending doing lines n rails or not at all. i have my mods on the above. i have a 2018
 

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Hey! thanks for the reply! hmm , im looking at the cobb fuel rails and lines and it does look like they split it in 2 Y blocks, therefore equal length lines along with the “oem” cobb pressure regulator and they have said that this is the only kit that really takes out the “stumble” getting their cobb fuel pressure regulator by itself, only band aids the “stumble”. Also on the other hand, the iag ptfe rails and lines kit(premade) are ran differently? are you also recommending doing lines n rails or not at all. i have my mods on the above. i have a 2018
ANY equal length lines will do it. I also know that the IAG rails have a provision to put fuel dampeners in them (and can be configured to equal length). For a stock turbo you DON'T need lines and rails. I ran 850cc injectors on a stock turbo (vf48) with stock lines and had plenty of pressure/ fuel... but I also did experience the stumble. But then I did the fuel line extension and that took it out.

Were I in your situation I'd go with e85 and no modifications to the fuel rails and lines... and only upgrade if you notice the stumble. You have enough pump and big enough injectors. But if you need to do injectors again; then I'd run lines and rails since you will have the intake manifold off. I ran mine under all that so you don't see it.
 

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Hey! thanks for the reply! hmm , im looking at the cobb fuel rails and lines and it does look like they split it in 2 Y blocks, therefore equal length lines along with the “oem” cobb pressure regulator and they have said that this is the only kit that really takes out the “stumble” getting their cobb fuel pressure regulator by itself, only band aids the “stumble”. Also on the other hand, the iag ptfe rails and lines kit(premade) are ran differently? are you also recommending doing lines n rails or not at all. i have my mods on the above. i have a 2018
The Cobb pressure reg kit is the right direction for removing the stumble, but what is most important is a capable tuner. I have basically the same setup as you suggested by who I thought was the best local STI tuner and still had the stumble. Took it back for him to rework the tune since it had other issues, as well and he said I would not be able to get rid of it without aftermarket rails. This from the guy who suggested my configuration to get rid of the stumble. His response was that some cars just need the rails.

I did some more research and found another tuner, a little further away. After speaking with him, he was confident he could smooth everything out. Sucks because it was now going to cost me another $1100 tune. But after he was done, the car was perfect. Super smooth clean power delivery. No more on/off notchiness and all the power was still there.

Make sure you work with a good tuner.
 

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I've had two identical cars where one will stumble and need work, and the other won't stumble at all. I have had cars where as I was working on the stumble, the owner put in rails/regulator/damper and the stumble went away. I've also had some where people don't listen and it's a shit show and a waste of time. Some cars like to do it more than others. I also recommend stock, series routing in most cases.

What I would do... Do the basics. Injectors, pump, and tune (on top of the "stage 2" stuff). If you experience the stumble, go from there. From a fuel delivery stand point, you don't need to go big on anything other than the basics mentioned above.

Subaru boards will sell you on all kinds of stuff you don't need. If it isn't broke, don't fix it and apply the "bang-for-buck" approach.
 

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Discussion Starter #10
The problem is, most people dont even know how the “stumble” feels like. so how does it even feel like? at the moment im protuned with 1050x/340aempump/cobbfpr/intake/dp/turboback/fuelpresssensor/wideband/4thcylcoolingmod/AOS. i still dont know how it feels like. maybe i have it? maybe i dont? but based on my research with stock turbo on flex, rails and fuel lines are not needed at all. some told me its not for gains, but its for effiency. im still kinda lost tho. my goal is to run with stock turbo and not to use ACN91 gas.
 

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If you don't feel, its nothing to worry about. Sometimes it so subtle, that only the tuner can feel it when sitting in a car that's strapped down. Typically, its a stumble that occurs somewhere around 3K RPM. Mine was in between 2500-3000 where the car would kind of fall on its face. Sometimes is very subtle, sometimes its a bit violent. Like YamahaSHO said above, it's not a rule that it's there, but it's likely when you start modifying.

It's more of a nuisance, than a concern...
 
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