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Thread: 7427 upgrade tuning help understanding

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  1. #1
    Fuel Injected!
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    7427 upgrade tuning help understanding

    I am using tunerpro rt, been using the forum for years and modifying bins when it was 7747 computer and had it running pretty good. But since I went to the 7427 I have been in the learning curve and trying to understand how things work. I have a 357 ATK bottom end, 9.7:1, vortec heads, comp cam 218/224 @ .50 114 lsa, edelbrouck eps performer, carb to tbi big block adaptor, bored 50mm tbi, cop car injectors at 21psi,vortec fuel pump msd 6al,700r4 with tcc lockup, running on 93 octane.

    I copied over my timing tables and ve from the 7747. Drivibility is pretty good lower rpm up to 3200, sounds clean, smooth, butt detection feels smooth, but I get 1000's of knock counts in a 9-10min drive(last test was 3867 knocks and only 5 had lowered the timing). maybe 5-10 drop the timing and only maybe 2 degrees which is good but why am I getting so many false knocks, I have changed to the 95 knock sensor got it from the truck I got the computer from.

    2nd questions is and I had the same thing on the 7747, unless I add 4-6 degrees at the distributor and then put it in as initial timing the truck just dosent have that extra umph. but once I do this the timing shown in the log is 4 degrees lower than what it should be, so am I basically giving the motor 4 degrees of timing it does not know about?

    I have added my wbO2 into the computer for datalogging and reads great. I also made a quick disconnect for my 3-wire heated o2 and the analog 0-1v output on the wbo2 controller. The 3 wire o2 is in the midtube headers I have and the wideband is aproxx 26in from the cylinder head. (about 10-12 in after the header) Which O2 is better to use for the motor, and how do I correct the values for the O2 because it is further down stream than the stock one would be?

    The learning curve is major over the 7747, thanks in advance for any help.

  2. #2
    Fuel Injected! brian617's Avatar
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    I would start with a new known correct 94-95 AUTO knock sensor. It would be hard for me to trust a used one since they made different knock sensors in the 94-95 truck depending on manual ECM and auto PCM.
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

  3. #3
    Fuel Injected!
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    ok slowly getting some of these fake knocks down, I say fake cause they do not pull timing. Is there a parameter in the data log that tells you if you are on open throttle or closed throttle SA table, would like to know if it is using that table or not. been using the 7427 wbo2 excel sheet dave w. made and really helping out.

    Been running in open-loop and runs really good, still looking for what to change for the narrowband o2 since it if further down stream than stock. Do I need to make corrections since I am in open-loop and it just shows 128 blm?

  4. #4
    Fuel Injected!
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    Quote Originally Posted by brian617 View Post
    I would start with a new known correct 94-95 AUTO knock sensor. It would be hard for me to trust a used one since they made different knock sensors in the 94-95 truck depending on manual ECM and auto PCM.
    Knock sensor.

  5. #5
    Super Moderator dave w's Avatar
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    Link I posted to the Stock 1998 Vortec L31 Timing Table: http://www.gearhead-efi.com/Fuel-Inj...-Throttle-ONLY!

    There might be other gearhead-efi posts with better performing (NON STOCK) L31 timing tables??? Perhaps those members will post in this thread with a READABLE L31 Performance Vortec timing table??? A copy / paste version of a L31 performance timing would be best for ALL members!

    dave w

  6. #6
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    Thanks dave. I have seen the thread you linked. with the 7747 I started with the vortec bin you posted and changed the timing table to fit my motor, I had it running without knocks. So when I swapped over to this computer I copied the timing table and VE for the starting point. Just wondering about these what I want to call false knocks since there is no timing removed.
    I just ordered a standard ks6 knock sensor will have it tuesday.
    Here is my SA table right now. I started in wot high kpa in the 30-32 range and have slowly brought it down from knock. I could run 30 degrees around 3400-3600 on the 7747 but seem to get knocks with this 7427. vortec_sa.PNG

  7. #7
    Super Moderator dave w's Avatar
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    Timing tables can be challenging. Most of the time, I start tuning with a factory timing table, like the Vortec L31 table I posted a link to and tune from there. Once the stock timing table has been tuned for a good fuel table, then I adjust the timing table for optimal spark advance / optimal fuel tables / optimal performance.

    Depending on the engine modifications, it might take several or even dozens of data logs to get achieve optimal performance.

    Tip, sometimes adding spark advance will reduce knock retard.
    Tip, sometimes spark advance changes of 1 degree or less will have a significant change in performance / knock.

    I authored an Excel WBO2 spreadsheet to help others tune the 16197427: http://www.gearhead-efi.com/Fuel-Inj...g)-Spreadsheet

    dave w

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