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Injector calculations

Discussion in 'A4/S4 forum(B5 Chassis)' started by jamie226bhp, Jul 6, 2011.

  1. jamie226bhp

    jamie226bhp Member

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    Right need some help or conformation think my injectors are about 280cc min at 4 bar which gives a total of 1120 cc min for 230 bhp I need 1679cc min I think so fitting 440 and a 3 bar reg should see 1680 cc min is this the righ calculation or am I way off, sorry if it sounds silly but I'm not a tuner or guru
     
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  3. aragorn

    aragorn "Stick a V8 in it!"
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    Mark is using Vauxhall C20LET injectors, which are rated at 304cc/min @ 3 bar and is running them at 4 bar (iirc) which pushes them up to ~350cc.

    His car made ~245 at MRC with no issues with fuelling.

    I've heard of C20LETs running 280ish hp on their stock injectors with silly fuel pressure.
     
  4. Bradderz_1988

    Bradderz_1988 Dont replace it, Upgrade it !!

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    Is marks car mapped or stock and what turbo Is he running ??
     
  5. aragorn

    aragorn "Stick a V8 in it!"
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    Its mapped, ish.

    Hes running a scroll hybrid, which is a little smaller than an FT.
     
  6. Bradderz_1988

    Bradderz_1988 Dont replace it, Upgrade it !!

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    What would the stock ecu run hp figure with FT, MAF, FMIC and injectors or would it need a slight tweak to fuel correctly ??
     
  7. bmarshall

    bmarshall Member

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    You would need a remap with a FT or it will run lean
     
  8. jamie226bhp

    jamie226bhp Member

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    Does anyone know what duty cycles the injectors are running when they quote 440cc min at 3 bar
     
  9. aragorn

    aragorn "Stick a V8 in it!"
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    They're rated at 100%.

    Bradderz: If you installed the Frankenturbo, MAF, and (properly sized) injectors on a standard ECU AJL you'd end up with around 220hp, however the ignition timing would end up quite far advanced, and you get a lot of timing pull even on 99octane fuel.

    Obviously this isnt particularly desirable, so if you did that it would be best to drive the car gently until you get it properly mapped.
     
  10. jamie226bhp

    jamie226bhp Member

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    So only 356cc at 80% cycle or about 470cc at 4 bar
     
  11. Bradderz_1988

    Bradderz_1988 Dont replace it, Upgrade it !!

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    But on the stock ecu/MAF/injectors I wouldn't see any of this with the FT fitted ?? Would only need to look at getting it mapped when I upgraded the MAF and injectors to sort out the Timing advance ?? Sorry for all the questions I'm young and still learning :)
     
  12. aragorn

    aragorn "Stick a V8 in it!"
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    Yes if the MAF and injectors are kept standard the fuelling and timing will be as stock, and you wont have a problem.

    The MAF upgrade effectively fools the ECU into thinking there is ~35% less air, so it turns up the boost trying to get back to what it thinks is the correct value. The timing issue occurs because its then running the timing for 10psi and 180hp when its actually running 14psi+ and 220+ hp.
     
  13. jamie226bhp

    jamie226bhp Member

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    So who does a 3" TIP to bolt to the maf or could I just use a reducer to fit to my standard size silicone one
     
  14. aragorn

    aragorn "Stick a V8 in it!"
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    reducer i guess.

    FT comes with a 3" tip, and i think perhaps 034motorsport do one.
     
  15. jamie226bhp

    jamie226bhp Member

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    Is it the same size on the turbo end though as mines only the standard size and not the bigger that I think the ft has, what dry cone filter do people run when they do the big turbo conversions as I might just loose the air box now
     
  16. aragorn

    aragorn "Stick a V8 in it!"
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    No idea, Ask mark what hes done, as hes running a 3" maf with an SP51.
     
  17. jamie226bhp

    jamie226bhp Member

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    Cheers I'll ask him
     

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