Page 1 of 3 123 LastLast
Results 1 to 10 of 22

Thread: injector flow rate table

  1. #1
    Senior Member
    Join Date
    Feb 2005
    Posts
    126

    Default injector flow rate table

    Just wanted some clarification. The injector flow rate table is a correction for the injector flow rate as a function of pressure (MAP). This correction is because injectors are calibrated at atmospheric pressure but in the engine, they are under varying levels of vaccum?

  2. #2
    Lifetime Member
    Join Date
    Jul 2004
    Posts
    640

    Default

    That would be correct.

    Ira

  3. #3
    Senior Member PSWired's Avatar
    Join Date
    Jan 2005
    Posts
    109

    Default

    I am guessing IFR tables are only used on returnless fuel systems where there is no vacuum references FPR?
    1995 GMC Yukon 4WD 4DR
    5.3 "LMG" engine: E85 with AFM
    6L80e 6 speed automatic transmission

  4. #4
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default

    My understanding of this subject (...ha...)...

    The IFR table tells the PCM how much fuel mass the injector flows as a function of vacuum (i.e. BARO - MAP).

    Injector flow rate depends on the pressure difference accross the injector: on one side of the injector there is manifold pressure (MAP), and
    on the other side is [constant] fuel pressure plus atmospheric pressure (since fuel pressure is measured relative to atmospheric pressure);
    i.e. diff = FP + BARO - MAP, where FP = constant

    At WOT, injector flow rate is less (MAP is high), and to spray a specific mass of fuel, the PCM needs to keep the injectors open longer;
    At idle, injector flow rate is more (MAP is low), and to spray a specific mass of fuel, the PCM needs to keep the injectors open shorter;
    i.e. time(s) = mass(g) / flow_rate(g/s)

    Since the pressure regulator is not MAP referenced (in our case, "returnless system"), the PCM uses the IFR table to compensate
    for the variation in injector flow rate caused by the variation of MAP;

    But, if the pressure regulator were MAP referenced, the regulator would increase fuel pressure as MAP increased, causing the pressure
    difference across an injector to always be constant regardless of MAP variation, and in this case the IFR table would be flat with no slope;
    i.e. diff = FP + BARO - MAP, where FP = constant + MAP, so diff = constant + BARO
    :?

  5. #5
    EFILive Distributor dfe1's Avatar
    Join Date
    Jan 2005
    Posts
    837

    Default

    The IFR table is simply the electronic equivalent of a vacuum line running between the intake manifold and the pressure regulator. Trucks have a vacuum referenced pressure regulator so the IFR table is a straight line.

  6. #6
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default

    dfe1 wrote:
    The IFR table is simply the electronic equivalent of a vacuum line running between the intake manifold and the pressure regulator.
    Spot on, that's the best summary I've seen.

  7. #7
    Junior Member daveb's Avatar
    Join Date
    Feb 2005
    Posts
    40

    Default

    I am wondering why the configs only go from 0-80 Kpa in the ifr tables, which is less than 1 bar.

    What do you do when using forced induction?

  8. #8
    Lifetime Member
    Join Date
    Apr 2003
    Posts
    379

    Default

    Quote Originally Posted by daveb
    I am wondering why the configs only go from 0-80 Kpa in the ifr tables, which is less than 1 bar.

    What do you do when using forced induction?
    Thats 0-80kpa of vacuum , for forced induction the whole maps need to be rescaled.

  9. #9
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    28,403

    Default

    VAC = BARO - MAP

    where
    VAC = vacuum
    BARO = barometric pressure (1 ATM, 1 bar, 100kPa approx, 15psi approx)
    MAP = manifold absolute pressure

    and since when MAP goes below 20kPa (VAC goes above 80kPa) the PCM cuts fuel (...correct me if I'm wrong...) so the PCM does not need the the injector flow rate below MAP 20kPa (which is VAC above 80kPa).

  10. #10
    Junior Member daveb's Avatar
    Join Date
    Feb 2005
    Posts
    40

    Default

    Thanks, I thought that might be the case.

    I assume injectors come with these ratings so the ifr table can be altered to suit.

    If we have a 2bar FI setup, I assume we scale this table as the 2 bar MAP sensor will report to the PCM the same voltage range as a 1 bar although it is covering 2 bar of pressure. Is that correct?

    Thanks,

Page 1 of 3 123 LastLast

Similar Threads

  1. B4001 Injector Flow Rate table help
    By kwhiteside in forum Gen III V8 Specific
    Replies: 14
    Last Post: June 30th, 2009, 10:45 AM
  2. injector flow rate table
    By stripes in forum Gen III V8 Specific
    Replies: 2
    Last Post: May 18th, 2008, 04:44 AM
  3. Injector Flow Rate correction of VE Table
    By oztracktuning in forum General (Petrol, Gas, Ethanol)
    Replies: 30
    Last Post: February 12th, 2006, 02:14 PM
  4. Injector Flow Rate Table
    By WicketMike in forum General (Petrol, Gas, Ethanol)
    Replies: 23
    Last Post: December 31st, 2005, 06:21 AM
  5. the injector flow rate table..
    By ZL1Killa in forum General (Petrol, Gas, Ethanol)
    Replies: 5
    Last Post: August 10th, 2005, 01:17 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •