Subaru sti/wrx injectors fitment?

Discussion in 'ENGINE' started by gorganl2000, Jan 10, 2018.

  1. gorganl2000

    gorganl2000 Registered User +

    does anyone know if Subaru sti/wrx new style injectors are a direct fit to our fuel rails?...or if any modification is required, exactly what needs to be done?

    also, is the injector electrical connector the same as stock?

    are these high impedance injectors

    sizes --- 565cc pinks and 565cc dark blues

    has anyone ran Subaru injectors in their starlet? if so, how do they perform (spray pattern, idle, ease/difficulty of tuning, etc)?
  2. Jay

    Jay Admin

    Haven't any experience of these being used unfortunately, the usual favourites are generally borrowed from Toyota models but I think Phil toyed about with RX8 units at one point.
  3. Rev

    Rev Registered User +

    Not sure on that but checking the max boost some time ago on Subaru injectors I found ratings of 15psi max which was a little limiting for the 1.3L potential.
  4. gorganl2000

    gorganl2000 Registered User +

    after a fair bit of searching on the two sites...seems they may fit, but you have to remove two spacers on the fuel rail?? (see gilly2006 post)
    Last edited: Jan 11, 2018
  5. gorganl2000

    gorganl2000 Registered User +

    on starlets, you can get around 15psi on a td04l with almost stock 295cc injectors....many people upgrade to 360cc/460cc/550cc and run way in excess of 15psi

    i'm not sure what subaru injectors are capable in a subaru engine,,,but dont they run around 14psi/15psi from the factory?
  6. Rev

    Rev Registered User +

    I have lost the original Subaru post but some figures I had say the fuel pump/rail limitation is around 65.25psi after that flow can decrease . With injector rating, a fuel pump rating and a fuel rail rating to consider.

    Injectors at 43.5psi base pressure would hit the limit 21.75boost +43.5 = 65.25psi limit. with everyone concentrating on fuel economy finer spray and higher fuel pressures get used, I remember being surprised some subaru injectors were only quoting 15psi boost max
    and about 60psi max. injector fuel pressure but this I think is not necessarily the injector maximum pressure differential possible. Yes 15psi boost as you say agrees with the post below for a Stock set up fuel pressure of 55psi (with stock fuel rail) through the injectors at wot. (40psi idle+15psi wot)

    Further the old link says these same STI Injectors attained 60psi fuel pressure with modded fuel rail.

    It also mentions injector dead times which are very different to our starlet injectors.
    Last edited: Jan 15, 2018
  7. gorganl2000

    gorganl2000 Registered User +

    well let me see if i can add something here..and this is just off the top of my head, i could be very wrong...lolol
    565cc injectors should in theory give around 360/400bhp at around 90.0% duty cycle depending on the formula you use, which on our small displacement engines will take quite some boost to achieve , maybe 25++psi

    now on a subaru sti engine which is maybe stock 280bhp at 15/17 psi and is 2000cc/ would use up this same injector flow much faster, given the need to fuel those bigger bores to achieve the same power 360hp, maybe 20+psi...also, a lot will depend on the other parts of the fuel system (engine efficiency, fuel pump, fuel rails etc)...the boxer engine is quite a different set up
  8. Rev

    Rev Registered User +

    The hks fcon way was to use stock fuel pressure with 550cc injectors so they became became 515cc.

    As far as I can tell when picking the injector size you take the worst case for the calculation and the actual power will be much less.
    eg 5 degC Intake Temp, inter-cooler efficiency say 90%, you allow injectors at a safe 80%DC , VE90% or depending on turbo , 4E revs maybe 8000 to match the aftermarket ecu, with fueling for performance at max lean torque say 13.2afr, flow margin for lower voltage situations, then and boost for desired power and to suit your fuel system and check you have enough fuel if the ecu goes to limp mode eg 10afr at wot.

    Injector spray I would think is idle related and over 8000rpm related apart from the spray pattern suiting the bore size. The stock injector spray has been proven in this range but i remember reading there were two 550cc injectors types one gave lumpy idle the other was smooth I guess the 565cc's have got this better now but my experience is the bigger injectors can draw more current, especially at idle this power to stay closed and deliver less fuel for our smaller engine strains the electrical system if not properly compensated by idle up corrections.

    Definitely like the power figures you are aiming for I was thinking of running 2 boost levels for weather to get a safety margin, increase cooling or push the safety limits but manufacturers can't do that so have to compromise.
    Last edited: Jan 16, 2018
  9. gorganl2000

    gorganl2000 Registered User +

    my research indicated a variety of injectors in the 540cc/565cc range
    some old rx7 550cc (old design like stock starlet 295cc)...some new model rx8 540cc...and new model subaru sti pink/dark blue 565cc
    idle and cruise control issues have been noted with regards to both types of rx7/8 injectors mentioned above........i've not read any cases, as yet, with the subaru injectors

    i'm not aiming for anywhere close to those power figures, of my goals has always been good drive-ability though
  10. Rev

    Rev Registered User +

    Cant really add a lot on particular Subaru injectors but have some observations on the early injectors that may interest you. eg For the early STI the Subaru injectors sites report maxing out their 560cc at 515cc at their stock pressure which was similar to the Starlet stock fuel presure. Again 515cc is also the max I remember the old hksfcons 550cc injectors at stock pressure. Then there are also early 560 evo injectors we get here that also run similar pressure and report maxing at 515cc.

    How setup effects injectors - That brings me to Muz_zz who posted on AU starlet site his Evo 560cc injectors were at 98% at 6200 rpm at 26lb / 26psi Well you can understand this when you look at his setup ( from his sale page ) -

    4e turbo
    Heads has had a 3 angle valve job new upgraded valve stem
    Stock cams
    Evo 560cc injectors
    Scat rods 74mm Wiseco pistons and rings
    WEPR Godzilla manifold HPC coated
    New Garrett GTX 2863r turbo with billet wheels .64 rear housing welded closed
    3inch exhaust
    Fuel rail and inlet manifold have been polished
    Standalone EMS 8860 ECU
    Alloy pulleys
    Adjustable cam timing gear
    Walbro 255 fuel pump

    So with this setup 560's (515ccPlus extra cc from the walbro raising stock fuel pressure ) hit their limit at 26psi 95%DC.
    Last edited: Jan 22, 2018
  11. AndrewDorasamy

    AndrewDorasamy Fresh Recruit

    hi there.

    I have purchased a set of denso subaru injectors and they do fit provides those spacers are removed as mentioned.

    There not much hassle they quick to go on and they good for spray pattern idling and tuning as well.

    I ran a Td04l turbo on 1.2bar boost and they coped well. Unfortunately my boost tap pipe cut off. Boost ran to 2.0bar and I ended up shooting the rod through the block.
    Calum122 and Jay like this.
  12. gorganl2000

    gorganl2000 Registered User +

    thanks for the confirmations on the subaru plug fitment

    sorry to hear of the engine/boost mishap
  13. AndrewDorasamy

    AndrewDorasamy Fresh Recruit

    Its ok lol I guess we gotta experience to learn. And I believe everything happens for a reason. After the mishap I ended up with 2 engines and a gearbox for a bargain. Blessing in disguise
    Jay likes this.

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