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Thread: 07? GMC Sierra surging/hunting idle

  1. #21
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    Quote Originally Posted by eXo3901 View Post
    Your flow rate table is set to one value, you only do that when you have a boost/manifold referenced fuel system. This table needs a factory style slope in your situation. Google says those are factory truck injectors. Do you have any information on the approximate flow rate when they are decapped?
    The table is maxed out to the same flow rate because the injectors flow more that the table allowed with it sloped. This was done per the tuning school method using flow rate vs Volts
    The injectors flowed 68lbs at 43psi and 78lbs at 58psi

  2. #22
    Quote Originally Posted by Timothy_james07 View Post
    The table is maxed out to the same flow rate because the injectors flow more that the table allowed with it sloped. This was done per the tuning school method using flow rate vs Volts
    The injectors flowed 68lbs at 43psi and 78lbs at 58psi
    Did you confirm that the voltage multiplier even works on your computer? Either way, it is still wrong because you do not have a manifold/boost referenced fuel system. The table needs a slope so the computer can compensate for MAP changes.

    Set all the injector tables back to stock. Multiply your entire flow rate table by 1.3265. That will get the 400kpa column to about 39lb/hr (half of 78lb/hr). This will retain the required factory injector slope. Then multiply your stoich table by 2. And lastly, divide your IVT Terms>AFR Term by 2. That is the double stoich method. You will need to re-tune after this.

  3. #23
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    Quote Originally Posted by eXo3901 View Post
    Did you confirm that the voltage multiplier even works on your computer? Either way, it is still wrong because you do not have a manifold/boost referenced fuel system. The table needs a slope so the computer can compensate for MAP changes.

    Set all the injector tables back to stock. Multiply your entire flow rate table by 1.3265. That will get the 400kpa column to about 39lb/hr (half of 78lb/hr). This will retain the required factory injector slope. Then multiply your stoich table by 2. And lastly, divide your IVT Terms>AFR Term by 2. That is the double stoich method. You will need to re-tune after this.
    I don’t believe it was checked to see if the multiplier works. This was another thing I was going to attempt as suggested. Will it work with the 2 bar OS?

  4. #24
    Yes.

  5. #25
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    Since that method cuts everything in half, how does that affect any airflow or fuel changes that are made afterwards? As far as if I would normally give or take 5% would it then need to be 2.5% ?

  6. #26
    The changes will be the same.

  7. #27
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    Juice new test2.hpt
    idle scan 2.hpl

    Did everything as suggested I believe and it?s still surging. file and log attached

  8. #28
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    It's approximately 6% too lean at idle. I'd add fuel to the VE table at idle and the surrounding cells.
    The spark over/under speed tables have been zero'd. That prevents the immediate spark correction from helping to stabilize the idle. Sometimes it can even be beneficial to increase these tables from stock in order to prevent surging.

    You should also increase the maximum expected MAP estimation to 255 kPa.

  9. #29
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    Quote Originally Posted by kevin87turbot View Post
    It's approximately 6% too lean at idle. I'd add fuel to the VE table at idle and the surrounding cells.
    The spark over/under speed tables have been zero'd. That prevents the immediate spark correction from helping to stabilize the idle. Sometimes it can even be beneficial to increase these tables from stock in order to prevent surging.

    You should also increase the maximum expected MAP estimation to 255 kPa.

    Increased the map max, put the factory tables back in the over/under spark. And I?ll figured out how to add fuel In that area of the VE. If I were to increase to spark table how much at a time would you suggest? And would that be across the whole table?

    if its a true cold start the surge is there until it hits 160*, as soon as it gets there the surge is almost gone. only does it sometimes once warm but corrects itself. ill attatch a new idle/driving log

    idle scan 3.hpl
    Last edited by Timothy_james07; 01-28-2022 at 01:49 PM.

  10. #30
    Try this file.
    Attached Files Attached Files

  11. #31
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    Quote Originally Posted by eXo3901 View Post
    Try this file.
    tried the file but couldnt get it to idle, heres the scan from that one

    idletry3.hpl
    Last edited by Timothy_james07; 01-28-2022 at 01:42 PM.

  12. #32
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    if its a true cold start the surge is there until it hits 160*, as soon as it gets there the surge is almost gone. only does it sometimes once warm but corrects itself. new idle/driving log attatched above

  13. #33
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    Was able to spend some time on it myself this afternoon and I finally feel like I’m getting somewhere. Can someone tell me what my injectors pw should be at idle? The idle is almost completely smooth and I believe they are around 2.0 with the fuel trims in the 5% range. Could I clean it up even more or leave it and try adjusting timing more as suggested?
    Also the wideband is showing 21.8-22 at idle
    Last edited by Timothy_james07; 01-28-2022 at 04:57 PM.

  14. #34
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    Where is the wideband sensor located? Do you have a datalog of it idling after it has warmed up?

  15. #35
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    It’s at the end of the downpipe. It’s an AEM gauge with the connector to tie it into the hp tuners. Yes it’s a couple post above. It’s called idle scan 3

  16. #36
    Your wideband is not logging data in the logs you post. So you would want to get that working for more help. I added another revision. If it does not work hopefully someone else steps in, I am out of ideas.
    Attached Files Attached Files

  17. #37
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    Quote Originally Posted by eXo3901 View Post
    Your wideband is not logging data in the logs you post. So you would want to get that working for more help. I added another revision. If it does not work hopefully someone else steps in, I am out of ideas.
    for some reason if I try to log with it in the scanner the afr glitches around but shows a solid number on the gauge itself. thanks for the help this far ill try it in the morning, ive reached out to kevin about doing a full tune for me as well

  18. #38
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    Just wanted to bump this up to say after trying everything suggested and still not being able to get it dialed in Kevin not only got the idle cleaned up, I also went ahead and got him to do the WOT tuning and the truck is running awesome. Wish I would of reached 2 months ago when the truck started getting tuned. Thanks again kevin you killed this tune!

  19. #39
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    Quote Originally Posted by Timothy_james07 View Post
    Just wanted to bump this up to say after trying everything suggested and still not being able to get it dialed in Kevin not only got the idle cleaned up, I also went ahead and got him to do the WOT tuning and the truck is running awesome. Wish I would of reached 2 months ago when the truck started getting tuned. Thanks again kevin you killed this tune!
    You're welcome. Thanks for your business!

  20. #40
    Any chance you would share the corrections for the original issue?