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Thread: Do s15 need hard wiring and relay for fuel pump upgrade?

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    Do s15 need hard wiring and relay for fuel pump upgrade?

    Hi im on s15 . My question is that , i am upgrading to 320 lph fuel pump . Do i need hard wiring (12 guage wire) and 12 amp relay. Or does s15 have oem hardwiring and relay beside the foot pedal.?
    Whats the procedure if needed?


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  2. #2
    Guest speedingmofa's Avatar
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    *Need* is a big word, but it is usually advised.
    The 320lph pump would surely use a higher amperage than the stocker. Not sure if the stock wiring can cope... So to be certain, most just hard wire it to ensure (more than) sufficient power is provided to run the pump.

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    Guest norfy's Avatar
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    i would swap the fuel pump and make notes of the voltage and current on both, then test the voltage coming down the feed wire to the pump with the ignition on to see what voltage is being delivered. Then see if you need to uprate the fuel circuit wiring.

    For reference, the wiring mod is usually done on vehicles such as the S13 due to the stock circuit only being able to supply around 11v where pumps such as the Walbro GSS341 data sheet shows it delivering full flow at 14.3v

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    I <3 BBS LM Actual_Ben_Taylor's Avatar
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    As above, test the voltage at the standard pump, I'll bet you find it's way lower than 14.3v

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    320 lph pump will likely over come your stock FPR if its hard wired too so I would check fuel pressure at idle and get an adjustable one if needed.

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    Thanks mates for replies... just checked 13.4 v is the current and aem installation manual suggests 13.2 to 14.3 v . Do i need to change the stock fpr too? Fpr was working fine till 1 bar.


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    Quote Originally Posted by sair View Post
    Thanks mates for replies... just checked 13.4 v is the current and aem installation manual suggests 13.2 to 14.3 v . Do i need to change the stock fpr too? Fpr was working fine till 1 bar.


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    When I fitted my 280lph pump I had a base pressure of 2.7 bar but it should of been (3 bar - vacuum at idle), which on my car should equal 2.3. So I bought a nismo adjustable fpr.

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