Fuel pump for stage 2?

[azsun]

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?).

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

[spirited09wrx]

No, I was looking at the walbro

[starkall]

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.

[UEDan]

You mean you won't need the ziptie mods? Ehhh I'd take the extra money.

Posted from a fone.

[MainFrame]

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.

[mangostick]

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.

[MainFrame]

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.

[azsun]

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.

[Anub1s]

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.

[MainFrame]

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.

[Anub1s]

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.

[azsun]

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...