Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: 2 bar E38 issues

  1. #1
    Lifetime Member
    Join Date
    Jan 2004
    Posts
    232

    Default 2 bar E38 issues

    Ok, I recently installed a magnacharger on my '07 GMC Sierra. I installed a 2 bar MAP sensor and properly scaled it in the computer. I also used the 2 bar Virtual VE(VVE) to update the coefficients. The MAF was also left installed.

    The issue I am seeing with this setup is that the truck will not go over .8 g/cyl until 4000 rpm. It starts out lean13:1 and gets leaner14:1 as rpms increase until 4000 rpm also. This is all at WOT. Once it passes the 4000 rpm mark the g/cyl jump to 1.10 and the AFR goes down to 11.5 or so. The jump to 1.10 g/cyl is very obvious. I am not sure what happens at 4000 rpm but, the "high speed mode rpm"(B8024) is set to 4000 rpm so I have a feeling that has something to do with it. PE was set to .80 and 40% throttle. I also tried adjusting the VVE table with no effect.

    I have went back to the stock 1 bar/MAF setup and am using PE for fueling over 40% TPS. The .8 g/cyl limit is not present with this setup. I can go WOT from a stop and almost instantly be over 1.00 g/cyl as boost rises.

    Anyone have any ideas what is up with the 2 bar setup?

    Here is the stock .tun file from the truck.
    Attached Files Attached Files

  2. #2
    Lifetime Member swingtan's Avatar
    Join Date
    Jul 2007
    Posts
    1,589

    Default

    First observation is that 4,000 RPM is the default "High Speed Mode" setting for air flow measurements. I believe that this is where the MAF is used solely for air flow measurements. Below this RPM, the MAF is used in conjunction with the VVE table to determine the air flow. Do you have any log files showing problem?

    Simon

  3. #3
    Lifetime Member
    Join Date
    Jan 2004
    Posts
    232

    Default

    The attatched log file shows a few different WOT blast where this happens. I know the fuel trims are wacked out but, am almost positive that it's a MAF placement/orientation issue. The MAF was located very close to a bend in the blower intake tube. I relocated it temporarily inline with the TB and it seems to work much better. Anyone else ran into these MAFs being sensitive to placement?

    Anyway, the log file below has a couple good instances of my described issue.

    One quick question. Do you have to do a FULL flash of the OS and Cal or just a Cal flash when you use the VVET to update the coefficients. I don't remember reading that in the instructions.

    Also, a couple of observations you might notice. INJPDELTA_DMA would not read below 400 kPa and E38.AFRATIO_DMA reads 0 all the time. Could it be a crazy OS causing these issues?

    Thanks
    Attached Files Attached Files
    Last edited by XLR8NSS; September 3rd, 2008 at 05:43 AM.

  4. #4
    Lifetime Member GMPX's Avatar
    Join Date
    Apr 2003
    Posts
    13,148

    Default

    Cal flash only to update the VVE.

    Can you please list a couple of frame numbers in that log where your problem shows.

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

  5. #5
    Lifetime Member
    Join Date
    Aug 2005
    Posts
    710

    Default

    This is very similar issue as trying to run MAF with a COS3 2 bar tune. Airmass calcs are limited to the 105kPa column when in boost, ignoring both the MAF and boost VE at that point til MAF is used exclusively.

  6. #6
    Lifetime Member
    Join Date
    Jan 2004
    Posts
    232

    Default

    Hey Ross

    Sorry not to list some frames, I am used to looking at my own files and know what to look for. Below are some frames range that have WOT blast with the problem. I have AFR logged over the serial connection.

    3944-3975

    4262-4318

    11637-11682

    19375-19417

    Thanks

  7. #7
    Lifetime Member
    Join Date
    Jan 2004
    Posts
    232

    Default

    3375-3440 has a pretty good shot too. That is from a stop rolling into it a bit then going WOT.

  8. #8
    Lifetime Member GMPX's Avatar
    Join Date
    Apr 2003
    Posts
    13,148

    Default

    What you could do is this.

    Put the 2bar MAP back on, rescale to suit.
    Force the MAF to fail (whilst leaving it in place) by setting C0301 to 1500 Hz and C0303 to 10.
    Fix the Virtual VE table for 2bar, because in stock form it's horrid. Also, you will need to make some changes to fix a bug in GM's VE lookup code see this thread -
    http://forum.efilive.com/showthread.php?t=8888

    Now you will be in SD mode you should be able to tune the VVE table as requried without MAF influence.
    If the problem goes away then the problem lies with running the MAF, maybe it's where it's located? I don't know, majority of the shops here is Aus doing 2bar E38 tuning are doing it Mafless.

    Also, before you get too far reshaping the VVE tables, consider bumping up the MAP Boundary 5 column in B8021 to maybe 130 KPa, it will help you shape the table in boost. I say do this before you make too many changes to the VVE table as it will alter quite a number of things once you make the change.

    Cheers,
    Ross
    Last edited by GMPX; September 3rd, 2008 at 04:14 PM.
    I no longer monitor the forum, please either post your question or create a support ticket.

  9. #9
    Lifetime Member
    Join Date
    Jan 2004
    Posts
    232

    Default

    Ross I will give that a shot but, probably won't be until this weekend. I'll report back

    Thanks

  10. #10
    Lifetime Member MN C5's Avatar
    Join Date
    Mar 2005
    Posts
    376

    Default

    Let us know what you find out... My motor is coming out tomorrow...

Page 1 of 3 123 LastLast

Similar Threads

  1. What have the issues been with LMM'S?
    By LBZoom in forum Duramax 06 LLY / 06+ LBZ & LMM
    Replies: 4
    Last Post: September 22nd, 2009, 01:06 PM
  2. A/C issues
    By Naf in forum Gen III V8 Specific
    Replies: 0
    Last Post: June 14th, 2009, 11:07 PM
  3. KR log issues
    By pullincrazy88 in forum Vortec V6/V8 Specific
    Replies: 3
    Last Post: October 3rd, 2008, 10:58 AM
  4. Still have IAC issues...
    By LS1_Dragster in forum Gen III V8 Specific
    Replies: 19
    Last Post: June 12th, 2008, 04:19 AM
  5. Ok some serious issues
    By Highlander in forum FlashScan V2 BB Logging
    Replies: 8
    Last Post: March 23rd, 2008, 04:45 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
  •