Strange fuel/ignition Cut

Discussion in 'Modification/ Technical Questions' started by suzieboy, Mar 14, 2019.

  1. suzieboy

    suzieboy Fresh Recruit

    Hi gents

    Need some assistance. Ive got a built bottom end 5e ,550cc injectors with a gt30 managed by E-Manage ultimate.
    Ive been gettin this fuel cut lately. No check engine light no knock. car drives fine but occasional i get some sort of fuel cut at around 4k rpm for 10 sec and the the power comes back on. Sometime i wont be on boost at all an i get this fuel cut. AFR are ok. the car doesn't break up. just this random fuel cut.
    Changed fuel pump
    changed FPR
    Changed king lead
    Changed fuel filter
    The emanage shows voltage from the map sensor.

    any ideas what could be possibly wrong? thanks.

  2. Skalabala

    Skalabala Registered User +

    What happens to the fuel pressure reading when it cuts?
  3. suzieboy

    suzieboy Fresh Recruit

    There is pressure still in the line. I checked it on the dyno. Injectors like they dont open.

    So i got an opinion that the high imp rx7 550cc injector my be tripping with the emanage ultimate.

    Theoretically the emu could only support injectors that are 150% the stock size. Stock starlet injectors are 295cc. Therefore the max that is recommended is 442.5cc

    Practically people are using over 442cc and getting away with it i assume. Seems like a hit and miss.

    Do i need an inject box/attachment to solve this issue?

    I would try another set of high imp injectors and report back.
  4. SKINY

    SKINY Registered User +

    Going down the injector route, is there an injector solenoid on these cars ? I know on gt-fours there is one and sometimes they go bad ?
  5. gorganl2000

    gorganl2000 Registered User +

    i've ran mazda gtx 360cc and madza rx7 460cc injectors on emu over the past decade which were 99.9% good-----on the odd 0.1% occasion i'd get a slight judder at low rpm when the car was cold (not yet to operating temperature) which would last all of a split second, felt like a quick "miss". for the most part, i was able to sort this out by a slight adjustment in the fuel and ignition map as it seems the stock ecu and emu were having a "fight" at that point in the map. These" old style" injectors with a single hole/port don't atomize fuel as well as the newer style injectors.

    since last year, i run subaru 565cc subaru injectors with emu, no issues at all...the subaru injectors are much nicer spray/atomization pattern (12 holes i think) and apparently easier to tune too, the drive on and off throttle is very smooth

    my emu has had the additional injector black box connected since it was installed in 2007/2008
  6. Rev

    Rev Registered User +

    The older black box was hks fcon piggyback but it runs 550cc low impedance at stock fuel pump pressure which gives fueling of 477.37 cc injectors ( both the hks 550cc and hks480cc matched the starlet inj lag etc,) plus it had a gcc to trim down to 420cc if needed.
    The electrical load is huge with larger injectors especially if fuel pressure is too high as they work harder and sometimes beyond there limits trying to stay closed to get the right AFR.
    I really like @ gorgan's solution of a modern injector that is easy to control at idle and is capable at max torque fueling.

    I would add I have heard some subaru injectors are limited on max. boost probably the smaller pinitle adds to back pressure? Also if you are lifting the rev limit substantially injectors have to be considered for that situation also.
    Last edited: Mar 18, 2019
  7. suzieboy

    suzieboy Fresh Recruit

    Haven't gotten another set of injectors. Mind you when the car was initially tuned to 400hp i wasnt having any issues with the same injectors.
  8. gorganl2000

    gorganl2000 Registered User +

    this is the reason i also run a genuine walbro fuel pump,,,given the age of our wiring, it flow is comparably better for the amperage it draws based on some high flow aftermarket fuel pump comparisons i found online
    my initial fear was the noisy reviews i've read about, but i must admit my walbro pump is not that noisy----but that may be due to the fact my gas tank is usually kept 1/4 and full
    with subaru 565 or 440cc injectors, i think they would satisfy the fuel needs of maybe 90%/95% of starlet projects out there.... unless going for some insane power levels
  9. suzieboy

    suzieboy Fresh Recruit

  10. suzieboy

    suzieboy Fresh Recruit

    Update: see attached log. So i realize the injector inputs are at 0%. but even before it happens fluctuates to 100%. Could it be electrical?

    Attached Files:

  11. gorganl2000

    gorganl2000 Registered User +

    isn't your car on the stock rev limiter at that rpm? the stock rev limiter a fuel or ignition cut?--i can't remember at the moment
  12. suzieboy

    suzieboy Fresh Recruit

    reving to stock limiter

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