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Discussion Starter #1
Anyone running the id1050x injectors or similar along with a better fuel pump on a 2015+ sti WITH stock rails/lines. I need to upgrade fueling system but the lines and rails are spendy. I just have a turbo back exhaust, catless, and a cobb sf intake. I'm getting protuned via e-tune rn. I'm just worried about running lean, and since adding the dp the car feels slow, much slower down low, possibly due to fueling, or I'm too early in the tuning process. Let me know if stock rails and line will work to get me by or if i need to wait and do it all together down the road. Thanks
 

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You'll be fine. You don't need a tune for rails and lines. If those mods are all you have, you don't really need to upgrade the rails or the lines.

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Injectors and upgraded fuel pump will be perfectly fine for your current set up. I dont think you need rails and lines unless you're going to power levels beyond the stock turbo capabilities.
 

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Upgrading the injectors and fuel pump certainly won't hurt and will allow for a little more power up top. However, I doubt the butt dyno slowness down low is a result of insufficient fueling. IDC typically peaks at higher RPMs with that setup on the stock injectors. Tuners can taper boost to scale back power in higher gears (4-6) to keep the IDC down. I'd talk to your e-tuner about your concerns before upgrading the fuel system. Do you have a wideband setup to monitor AFRs during your e-tuning?

Here's a post from BrenTuning comparing stage 2+ setups with & without an upgraded fuel pump & injectors:

BrenTuning;43504613 said:
We can tune Stage2+SF setups safely with IDC at a safe level even on stock fueling. With stock fueling, the power just has to be scaled back a bit. While peak number differences aren't huge, the midrange gains are 15WHP/20WTQ throughout.

IDC on the Stage2+SF stock injector setup was right around 95% at the top of 4th gear. With the ID1000 injectors and DW65C pump, the IDC was around 60%. As for tuning differences go, you have to run a leaner mixture and taper the boost on the stock fueling car, with ID1000 you can run a bit more timing and boost.

Then there's the debate on how Subaru's IDCs are calculated (based on IPW & RPM) and many tuners have gone well over 100% IDC. IDC is a calculated value (with a margin of error), not a raw counter produced by the ECU. I've seen tuners go as high as 120% IDC, but of course those tunes run a higher risk of running lean. In that case, you need to pay close attention to the AFRs, especially in colder weather and at high load in higher gears.

Edit: If you're upgrading the pump & injectors, you'll also want to look into an FPR "stumble fix" by Cobb or IAP/IATuning.
 

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You'll be fine. You don't need a tune for rails and lines. If those mods are all you have, you don't really need to upgrade the rails or the lines.

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Disagree on the tuning note, (Shocker there eh?) especially if going to a parallel delivery system.
 

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Disagree on the tuning note, (Shocker there eh?) especially if going to a parallel delivery system.
You can if you want. "Never hurts," as they say. I've data logged both setups (factory rails vs aftermarket), mind you on a ~Stage 2 setup (maybe 250whp??), monitoring knock, AFR w/ WBO2, fuel trims, etc, at idle and WOT, the differences were of little concern. Maybe higher HP setups may make a difference but I haven't had the opportunity to work with that on Subaru platforms.

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Discussion Starter #10
So i can run injectors and a aem fuel pump with stock lines and rails? I would get a re-tune for sure. Im also prolly gonna slap on an ewg up-pipe to get rid of boost creep, and do turbo inlet since the intake manifold will be off already anyways lol. Can i run an ethanol blend with stock lines on this set up or is that where i need to upgrade lines/rails?
Full set up on a 2018 sti would be, cobb intake, tomei catless downpipe, id1050x injectors, aem 340 fuel pump, prolly cobb turbo inlet, grimspeed EWG up-pipe....prolly gonna go with tial WG....oh and a 3 port ebcs....
Would it even be worth it to get an ethanol tune without the sensor kit? And then as said before, there is the question if the stock lines/rails would work or just melt haha thanks again. And do i need to upgrade FPR, what ones would work with stock lines?
 

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If you're upgrading the injectors & fuel pump.. go ahead and get the flex fuel sensor kit. You'll also need to upgrade the FPR to combat the "stumble" since you're upgrading the injectors.

The stock lines & rails are fine and ethanol safe.
 

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The injectors are what necessitate the tune.

Send me a log of your boost creep ([email protected]). I have serious doubts you're experiencing boost creep on this setup. Everybody likes to push EWGs.. I find they are rarely needed.


So i can run injectors and a aem fuel pump with stock lines and rails? I would get a re-tune for sure. Im also prolly gonna slap on an ewg up-pipe to get rid of boost creep, and do turbo inlet since the intake manifold will be off already anyways lol. Can i run an ethanol blend with stock lines on this set up or is that where i need to upgrade lines/rails?
Full set up on a 2018 sti would be, cobb intake, tomei catless downpipe, id1050x injectors, aem 340 fuel pump, prolly cobb turbo inlet, grimspeed EWG up-pipe....prolly gonna go with tial WG....oh and a 3 port ebcs....
Would it even be worth it to get an ethanol tune without the sensor kit? And then as said before, there is the question if the stock lines/rails would work or just melt haha thanks again. And do i need to upgrade FPR, what ones would work with stock lines?
 

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Discussion Starter #13 (Edited)
My tuner says i only boost creep a little around 5k rpms and not bad compared to some cars he said. If i don't have to get the up/pipe ewg, that'd save me some money for sure. I just want my car to be done with, at least for the year haha. I'm just worried about the IDC since I'm mainly about reliability since it's my daily and i dont wanna worry about it when i run it hard at autocross (i dc if i win or lose there, it's just hella fun). Would the inlet be worth it? Or just do fuel pump, injectors, FPR, and flex fuel kit, and let it be till next year....do i need the fpr as well? And do i also need an 3 port ebcs?
 

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Share a log and many of these concerns can be answered.... ;)

My tuner says i only boost creep a little around 5k rpms and not bad compared to some cars he said. If i don't have to get the up/pipe ewg, that'd save me some money for sure. I just want my car to be done with, at least for the year haha. I'm just worried about the IDC since I'm mainly about reliability since it's my daily and i dont wanna worry about it when i run it hard at autocross (i dc if i win or lose there, it's just hella fun). Would the inlet be worth it? Or just do fuel pump, injectors, FPR, and flex fuel kit, and let it be till next year....do i need the fpr as well? Or the stumble fix?
 
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