Fuel pump for stage 2? - Page 2
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This is a discussion on Fuel pump for stage 2? within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Originally Posted by Impreza2.0 I have a modification path you don't want to follow, but I found out the hard ...

  1. #16
    Registered User azsun's Avatar
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    Quote Originally Posted by Impreza2.0 View Post
    I have a modification path you don't want to follow, but I found out the hard way in a sad attempt at a stage 2 tune, and WOT in 3rd at 6500rpms on the stock gear ratio is enough to make the ECU freak out. I assume that is what happened, there was a severe fuel cut and the car stuttered, stalled, restarted due to already-present fuel, and was OK again. Upon asking my mechanic what that was being caused by, he reminded me about our previous conversations about injectors/pump/tune and that all 3 should be done at once, that 550cc injectors are just over the ability of the stock pump once an tuning is up for the doing. You CAN do it, but for headroom as stated, and safety as stated, basically the same thing stated two different ways, it isn't a foolish 45 minutes and under $200 investment in the durability of the fueling system. This is one of those "don't cheap out" things, since it isn't something you can just whip back together on the side of the road without tools. My opinion, your car. Anything that breathes better is going to need to drink more. Especially if you put more fire under it's butt.
    Understood, def agree. Love putting fire under butt's...

    Alright thanks for the replies guys. Will give them a call back and see what pump they'd be installing (he quoted be ~$125 for the pump I believe?).


    Quote Originally Posted by spirited09wrx View Post
    not exactly a thread jack since it affects the OP...

    I was looking online at the walbro and it said 02-07 and 08+ with modifications...what are those modifications or is the site I was looking at have wrong info?
    Is this the pump?
    HFP 255LPH Intank Fuel Pump Subaru WRX Sti 2001 - 2009
    -Corey

    2011 WRB WRX - Stage 2+
    Invidia TBE, AEM CAI, PW TMIC
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  3. #17
    Cheeky Bastage! spirited09wrx's Avatar
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    No, I was looking at the walbro
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  4. #18
    Registered User starkall's Avatar
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    Quote Originally Posted by MainFrame View Post
    No, the stock ECU is more than capable of handling far beyond simple stage two modifications..






    I'm not sure of the logic behind this, considering the Walbro 255lph pump is more than adequate for half the price.
    Because you don't have to mod the basket for the DW 65c fuel pump. It drops right in.

  5. #19
    Registered User UEDan's Avatar
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    You mean you won't need the ziptie mods? Ehhh I'd take the extra money.

    Posted from a fone.

  6. #20
    Subaru Newb MainFrame's Avatar
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    Quote Originally Posted by starkall View Post
    Because you don't have to mod the basket for the DW 65c fuel pump. It drops right in.

    Meh. . If the price difference was <$20 then it might be worth it.

  7. #21
    The Fruit mangostick's Avatar
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    I dont see how fuel pump has anything to do with injector duty cycle... the pressure and volume delivery are where the fuel pump chimes in.

    That said, you can NEVER have enough fuel delivery on tap. The less the pump has to stress to deliver on demand the better. Run the walbro, especially if you plan to go further with your mods down the line. Its cheap insurance.

    If you want to reduce duty cycle though, only a bigger injector will do that.. and they're not necessary for stage II.
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  8. #22
    Subaru Newb MainFrame's Avatar
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    Quote Originally Posted by mangostick View Post
    I dont see how fuel pump has anything to do with injector duty cycle... the pressure and volume delivery are where the fuel pump chimes in.


    The fuel pump has everything to do with injector duty cycle once you start maxing out it's flow and the pressure drops. When the pressure falls IDC must increase to maintain the same AFR.

  9. #23
    Registered User azsun's Avatar
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    So consensus is that it at the least is kinda cheap and will help the safety of the car/performance? Does kinda make sense now.
    -Corey

    2011 WRB WRX - Stage 2+
    Invidia TBE, AEM CAI, PW TMIC
    295whp/305w torque

  10. #24
    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Quote Originally Posted by mangostick View Post
    I dont see how fuel pump has anything to do with injector duty cycle... the pressure and volume delivery are where the fuel pump chimes in.

    That said, you can NEVER have enough fuel delivery on tap. The less the pump has to stress to deliver on demand the better. Run the walbro, especially if you plan to go further with your mods down the line. Its cheap insurance.

    If you want to reduce duty cycle though, only a bigger injector will do that.. and they're not necessary for stage II.
    Like Mainframe pointed out, you're a bit wrong there. With a high flow pump, you can push your injectors closer to their max without worrying about starvation. There is a point where max IDC is just max IDC, where you've reached the end of what the injectors can actually flow. However, if your injectors are large and the pump you have is not sufficient to keep the flow of fuel at the needed constant, the injectors will have to remain open longer to keep up with demand, hence increased IDC. In that instance, a higher flowing pump will reduce IDC. It's one of those relative things.

    Like you said though, it's cheap insurance and for the price point the options it opens up for modifications down the line makes it a pretty easy decision early on. Especially on the newer generation cars where stage 2 very nearly or entirely maxes out the injectors and the pump.
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  11. #25
    Subaru Newb MainFrame's Avatar
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    I would get it, especially if your tuner recommends it (much less requires!). Even if you won't technically max out the OEM fuel pump at stage two, overly sufficient flow is necessary for a safe tune. If you're at the limits of your fuel pump and something goes wrong [cold weather/up hill over boost, vacuum like pops off, etc] then you're going to hit high load super lean, which can kill an engine all at once. If you have extra pump and your tuner has taken the time to make a safe tune then you will overboost, but the fuel will be there and potentially save your ass. It's good tuning practice to go overkill on the fuel system at least a little.

  12. #26
    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Quote Originally Posted by wrxtreme06 View Post
    he said GOODspeed, not GODspeed. lol

    i've never heard of anyone requiring an aftermarket fuel pump for stage II. my tuner protuned mine on the OEM one.
    Just wanted to point this out: there is a fair bit of difference between your (our) generation and the newer generation with regards to fuel demands and engine capabilities. Notably that the turbochargers are leagues better on the newer cars.
    Cody
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  13. #27
    Registered User azsun's Avatar
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    Quote Originally Posted by MainFrame View Post
    I would get it, especially if your tuner recommends it (much less requires!). Even if you won't technically max out the OEM fuel pump at stage two, overly sufficient flow is necessary for a safe tune. If you're at the limits of your fuel pump and something goes wrong [cold weather/up hill over boost, vacuum like pops off, etc] then you're going to hit high load super lean, which can kill an engine all at once. If you have extra pump and your tuner has taken the time to make a safe tune then you will overboost, but the fuel will be there and potentially save your ass. It's good tuning practice to go overkill on the fuel system at least a little.
    Yup! Am just waiting for a quote now...
    -Corey

    2011 WRB WRX - Stage 2+
    Invidia TBE, AEM CAI, PW TMIC
    295whp/305w torque

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