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Old 01-16-2013, 03:03 PM   #1
rshoop
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Member#: 99383
Join Date: Oct 2005
Default fuel pressure regulator

I'm doing upgrades on my 06 sti. walbro 255 fuel pump, 800cc injectors,3" intake and inlet,fmic, garrett gt3582 turbo,up pipe with 44mm external wastgate,3" turbo back exhaust, hks ak005 boost control and cobb access port. the question is do I need to change the fuel pressure regulator or will the stock one work? thanks
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Old 01-16-2013, 03:54 PM   #2
the suicidal eggroll
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2012 WRX

Default

Whether or not you need to change the FPR depends on two things

1) your fuel pump, and whether or not it flows too much for the FPR to bypass to keep the pressure down
2) you need a higher base fuel pressure (not enough injector for your power requirements)

You don't meet either of these criteria, so you're fine with the stock one. That is assuming your 800cc injectors can keep up, but even if they can't you won't be able to bump up the pressure much at all before hitting the limits of the fuel pump, so it doesn't really matter.
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Old 01-16-2013, 04:03 PM   #3
Zackbo
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Kinda Silver-ish

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Ditto with the eggroll. I'm running a similar setup and those injectors will max out around 24psi. Go SD with the accessport. It will make life much easier in the long run.
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Old 01-16-2013, 06:34 PM   #4
rshoop
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sorry, what does SD mean?
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Old 01-16-2013, 07:06 PM   #5
the suicidal eggroll
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Speed Density - It's a fueling method in which the ECU calculates the amount of air entering the engine using the current manifold pressure, air temperature, RPM, engine displacement, and a 2d volumetric efficiency table in the ECU.

This is instead of the stock fueling method which uses a mass air flow sensor located in the intake pipe to measure the velocity of the air near the middle of the pipe and extrapolate that information to estimate the total mass flow rate of the air entering the engine.

SD is much more stable and reliable at high air flow rates where traditional MAF setups can encounter turbulence. SD is also immune to air leaks anywhere in the intake tract (at least from a fueling perspective). The downsides are that the VE table will need to be re-tuned for even the most minor of modifications, such as a new intake manifold, TGV deletes, valve job, header install, EWG, etc. SD can also be a little finicky at very low air flow rates, such as idle and very light cruise. Some engine management systems allow you to run a hybrid setup that utilizes the MAF at low flow rates, and transitions to SD at medium/high flow rates. I'm not sure if the accessport has this ability though.
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