Results 1 to 9 of 9

Thread: Main Injection Fuel Flow Rate Question

  1. #1
    Junior Member
    Join Date
    Nov 2005
    Posts
    20

    Default Main Injection Fuel Flow Rate Question

    I finally got to the track to do some tuning with EFILive. One thing I noticed was that the Main Injection Fuel Flow Rate was only going to 79.7 mm3 for the entire run. And since this is one of the values it uses to calculate Main Injection On Time I wasn't getting the amount of fuel I thought I should. Anyone have any ideas?

  2. #2
    Lifetime Member GMPX's Avatar
    Join Date
    Apr 2003
    Posts
    13,148

    Default

    Unfortunately that has been an issue for all Diesel tuners, TechII suffers the same problem, however, we fixed it :-)
    Choose the PID "Main Injection Fuel Flow Rate 2" GM.FUELQ_MAIN_DMA
    This will give you values beyond the 79.7 limit, however, it uses 2 channels of data. Remember to unselect the standard GM mm3 PID if you are logging this one.
    Same problem occurs for boost, you are better off logging GM.BOOST_DMA

    Also, the 79.7mm3 limit you saw is just a scantool issue with the ECM, it is still processing numbers higher than that for the fuel calculations.

    Cheers,
    Ross
    I no longer monitor the forum, please either post your question or create a support ticket.

  3. #3
    Junior Member
    Join Date
    Nov 2005
    Posts
    20

    Default

    Thanks I will try that.

  4. #4
    Junior Member
    Join Date
    Nov 2005
    Posts
    20

    Default

    The other issue I was seeing was that in 5th gear, top end of the track, I felt the truck start to lay over. Looking at the data I noticed that the fuel delivery decreasing, the EGTs proving that. At the end of the track my EGTs were only 1050 degrees F. The main rate started decreasing and in turn so did the on time. Any thoughts?

  5. #5
    Lifetime Member GMC-2002-Dmax's Avatar
    Join Date
    Dec 2005
    Posts
    1,294

    Default

    If you did not set any codes then the truck is running out of fuel pressure because you may have commanded too large of a main rate pulse width and if so then the truck will lay over.

    Try adding a lift pump to help supply the low pressure side of the CP3 which is the high pressure pump for the injectors.

    There are several options available and if you need help just send me a PM or Trippin.

    Good Luck,

    T NY
    Last edited by GMC-2002-Dmax; August 25th, 2006 at 11:19 AM.
    www.mscservices.net


    Tuner of many, many Duramax and Cummins Diesels.


  6. #6
    Junior Member
    Join Date
    Nov 2005
    Posts
    20

    Default

    There were no codes set and I have a lift pump setup. I just reviewed my log from my last run and when the EGTs starting dropping the the desired fuel pressure was 159 Mpa and my actual was in the 140's. After the EGTs had dropped to 1200 and below the calculated fuel rate was dropping and the actual fuel pressure actually spiked to 180 Mpa. The main injection on time was dropping drastically due to the calculated fuel rate dropping I would guess.

  7. #7
    Lifetime Member GMC-2002-Dmax's Avatar
    Join Date
    Dec 2005
    Posts
    1,294

    Default

    If you can send me your email I can send you a PID for logging.

    It appears that the mm3 rate is being reduced for some reason, if you would like I can look over your log file and see if I can help you diagnose the problem.

    Just let me know and I will PM you my email for the log file.

    T NY
    www.mscservices.net


    Tuner of many, many Duramax and Cummins Diesels.


  8. #8
    Junior Member
    Join Date
    Nov 2005
    Posts
    20

    Default

    PM sent.

  9. #9
    Senior Member
    Join Date
    Mar 2006
    Posts
    103

    Default

    how bout doing a bottle test?
    2017 Trailblazer 2.5L Dmax
    07 LBZ rc lb EFI - Sold
    05 lly cc lb, EFI 80hp tune-Sold
    01 lb7 rc lb EFI & Road Runner,1000+hp -Sold
    Duramax power

Similar Threads

  1. Injector flow rate maxxed out fuel gauge error
    By hymey in forum E37, E38 & E67 PFI ECM's
    Replies: 19
    Last Post: December 10th, 2010, 04:01 AM
  2. injector flow rate question
    By EVI in forum E37, E38 & E67 PFI ECM's
    Replies: 2
    Last Post: May 29th, 2009, 04:40 PM
  3. ** Main Injection ** n00b Help **
    By Nemo in forum Duramax LLY
    Replies: 3
    Last Post: December 21st, 2008, 02:43 PM
  4. Injector Flow Rate question
    By Perdieu in forum Custom Operating Systems
    Replies: 5
    Last Post: April 1st, 2007, 11:31 AM
  5. injector flow rate question
    By 9secVette in forum General (Petrol, Gas, Ethanol)
    Replies: 2
    Last Post: May 24th, 2006, 01:04 AM

Posting Permissions

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