Results 1 to 4 of 4

Thread: '7060 to '7427 conversion - remaining fuel trim issues

  1. #1
    Fuel Injected!
    Join Date
    Apr 2017
    Posts
    124

    '7060 to '7427 conversion - remaining fuel trim issues

    In a previous post, I mentioned I was taking a break from spark advance tuning and 10s of thousands of fake knock counts. Now have knock retard turned off and am running stock L31 timing tables which are more conservative than what I had before. I'm now working on getting all fuel trim related items right before I go back to tackling spark and knock. Remaining issues are below. Any help or advice on any of these would be much appreciated!

    1. Cold start issues. Actually starts fine, minimal cranking. But after a couple of seconds of normal operation I get a swinging idle and it will almost stall. WBO2 pegs lean when it wants to die, then swings rich when it recovers. I haven't verified, but I think stall saver is kicking in? I can resolve this a little by raising the idle with my foot, but until it warms up it will go through these cycles. In drive is worse and reverse is by far the worst. All these problems are resolved when it goes into closed loop EXCEPT reverse. Even fully warm, reverse with zero TPS it will want to die.

    2. Hesitation at slow takeoff from stop. If I punch it from stop, no issues. But a slow gradual take-off will produce a noticeable (even to passengers) hesitation. I'm guessing this is due to a problem in transition from idle VE table to off idle table, but I'm struggling with how to resolve it.

    3. Rich Deceleration. Most of the time taking my foot off the gas completely results in AFRs on the WB in the 11s or even high 10s. This continues all the way to almost full stop, but at 5 mph and slower AFR is going back up to 13s and 14s. At full stop it idles nicely in the 14s usually. As far as DFCO is concerned it's either never coming on or it's very seldom. I will play with DFCO but it seems like I should be resolving the rich decel first, without DFCO.

    4. And now a general question for a NOOB to WBO2 tuning. I have the spreadsheet that works with the '7427 (Dave W) and I understand the general principal of making adjustments to get AFRs around stoich across the board. But the part I don't understand - we're making the changes to the VE table and we're using CL to tune. Won't the computer be making adjustments all the time based on the NB and theoretically the WB would just be seeing the the already corrected values? It doesn't seem like it would be capturing much to adjust? Would using OL to WBO2 tune work? It seems like you'd zero in on the corrections needed to the VE tables much more quickly that way.
    Last edited by Daveo91; 1 Week Ago at 08:58 AM.

  2. #2
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    5,593
    Interesting Pictures Below.

    Same data logs BLM vs. AFR

    Approximately 170,000 data points!

    dave w

    BLM - Near Idle.jpg

    BLM - Off Idle.jpg

    Near Idle.jpg

    Off Idle.jpg

    PE Active.jpg

  3. #3
    Fuel Injected!
    Join Date
    Apr 2017
    Posts
    124
    Quote Originally Posted by dave w View Post
    Interesting Pictures Below.

    Same data logs BLM vs. AFR

    Approximately 170,000 data points!

    dave w

    BLM - Near Idle.jpg

    BLM - Off Idle.jpg

    Near Idle.jpg

    Off Idle.jpg

    PE Active.jpg
    Thanks for the comparisons, Dave. I think what I'm supposed to be seeing is the wider range of info the WB data logs are providing? I guess what I'm still not understanding is if we adjust the VE tables based on that info, will the NB closed loop system just wash them out and do what it thinks is correct? Another thing I'm not understanding is: how do we make adjustments to the areas that we DON'T want AFR to be 14.7, like decel, highway cruise, and PE? Aren't the adjustments we're making skewing everything towards 14.7?

  4. #4
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    5,593
    Quote Originally Posted by Daveo91 View Post
    Thanks for the comparisons, Dave. I think what I'm supposed to be seeing is the wider range of info the WB data logs are providing? I guess what I'm still not understanding is if we adjust the VE tables based on that info, will the NB closed loop system just wash them out and do what it thinks is correct? Another thing I'm not understanding is: how do we make adjustments to the areas that we DON'T want AFR to be 14.7, like decel, highway cruise, and PE? Aren't the adjustments we're making skewing everything towards 14.7?
    I look at AFR's and BLM's as measurements. I consider AFR's more accurate then BLM's. Adjusting closed loop with AFR's is " same / same" as adjusting closed loop with BLM's. AFR's and BLM's are measurements. When closed loop AFR's are lean, add fuel to the VE Table When closed loop BLM's are lean, add fuel to the VE Table.

    Course Tune / Fine Tune. Course tune is basically correcting the VE Tables. The computer bases the areas that we DON'T want AFR to be 14.7, like decel, highway cruise, and PE on an accurate Course Tuned VE Table. Fine Tune adjusts the areas that we DON'T want AFR to be 14.7, like decel, highway cruise, and PE.

    dave w

Similar Threads

  1. upgrade to '7427 from '7060 - ready to pull the trigger
    By Daveo91 in forum GM EFI Systems
    Replies: 22
    Last Post: 08-30-2021, 07:32 PM
  2. Replies: 18
    Last Post: 07-13-2021, 09:46 AM
  3. BLM- Long term fuel trim?
    By rudder2fly in forum GM EFI Systems
    Replies: 32
    Last Post: 07-11-2018, 10:50 PM
  4. Replies: 5
    Last Post: 01-27-2016, 05:03 AM
  5. 7060 MPFI Conversion?
    By 1BadAction in forum GM EFI Systems
    Replies: 4
    Last Post: 04-27-2013, 01:50 AM

Bookmarks

Posting Permissions

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