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Thread: Trimming too much fuel in closed loop

  1. #1
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    Trimming too much fuel in closed loop

    427 DART block with a 244/254 cam.

    Open loop is pretty good but in closed loop it trims too much fuel off both banks and causes a bad stumble under load and the car goes super lean on the wideband.

    Ideas? I'm attaching the scan file and tune.

  2. #2
    Senior Tuner Lakegoat's Avatar
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    Your tune shows that it is running in SD mode. You probably need to adjust your VE table so that it runs correctly. I see that your idle spark is way into the 30's. I ran that 244/250 cam in a smaller motor with only 19 degrees. Maybe cut back on the timing a little.
    When it goes into closed loop, it shows that it is pulling fuel---rich. That could be your stumble.
    Last edited by Lakegoat; 1 Week Ago at 07:52 AM.
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  3. #3
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    Quote Originally Posted by Gripenfelter View Post
    427 DART block with a 244/254 cam.

    Open loop is pretty good but in closed loop it trims too much fuel off both banks and causes a bad stumble under load and the car goes super lean on the wideband.

    Ideas? I'm attaching the scan file and tune.
    Your channel list is very limited. Are you running an ETC? Brand of 95lb/hr injectors and did they come with Data? Are you running a FPR fuel rail or returnless? Would you try these channels to get a better idea of what's going on? There are 2 sets. 1 for Idle and another for working on Fuel trims. Let's see what each can tell us.
    Idle (and include LTFT if you would enable that in tune):
    Engine Run Time
    Fuel System #1 Status (SAE)
    LTIT Gear/ACoff
    Idle Adapt (STIT)
    Idle Base Gear Airflow
    Idle Startup Airflow
    Idle Desired Airflow
    Dynamic Airflow
    Idle Air Control Position
    Idle Air Control Desired Position
    Engine Coolant Temp (SAE)
    Mass Airflow (SAE)
    Mass Airflow Sensor
    Engine RPM (SAE)
    Cylinder Airmass
    Timing Advance (SAE)
    Throttle Position Sensor (volts)
    Throttle Position (SAE)
    Vehicle Speed (SAE)
    Intake Manifold Absolute Pressure (SAE)
    Intake Air Temp (SAE)
    O2 Voltage B1S1 (SAE)
    O2 Voltage B2S1 (SAE)
    Short Term Fuel Trim Bank 1 (SAE)
    Short Term Fuel Trim Bank 2 (SAE)
    Long Term Fuel Trim Bank 1 (SAE)
    Long Term Fuel Trim Bank 2 (SAE)
    Fuel Trims:
    Engine RPM (SAE)
    Vehicle Speed (SAE)
    Idle Air Control Position
    Idle Air Control Desired Position
    Idle Cracker Airflow
    Idle Follower Airflow
    Cylinder Airmass
    Mass Airflow
    Mass Airflow Sensor
    Dynamic Airflow
    Intake Manifold Absolute Pressure (SAE)
    Timing Advance (SAE)
    Torque Mgt Advance
    Knock Learn Factor
    Injector Flow Rate
    Injector Pulse Width Avg. Bank 1
    Injector Pulse Width Avg. Bank 2
    Knock Retard
    *Accelerator Pedal Position (IF ETC installed)
    Throttle Position (SAE)
    Equivalence Ratio Commanded (SAE)
    Air-Fuel Ratio Commanded
    Fuel System #1 Status (SAE)
    Short Term Fuel Trim Bank 1 (SAE)
    Long Term Fuel Trim Bank 1 (SAE)
    Short Term Fuel Trim Bank 2 (SAE)
    Long Term Fuel Trim Bank 2 (SAE)
    Last edited by Hondaeater; 1 Week Ago at 09:27 AM. Reason: more info request

  4. #4
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    Thanks guys. I?ll do a new log tonight with more channels.

    The car has a 244/256 cam.
    Return style fuel system -8AN feed -6AN return running at 58 psi.

    SD 80 injectors. All motor. Speed density only no MAF.

    The motor put out 698 hp on an engine dyno before I dropped it in.

    Someone else had suggested to me that I run a hybrid closed loop system where the car doesn?t go into closed loop until above 2000 rpm and 165 F. Not sure how I would do that. He said it was because the cam is so big and wants to run rich at idle and the O2 sensors are set so far back because of the long tube headers.

  5. #5
    Senior Tuner Ben Charles's Avatar
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    Is this the same gentlemen from camaroz28 boards years ago from the lt1 days?
    Hit me up, I’m sure I can help on your setup

    Email Tunes, Bencharles_10@hotmail.com
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  6. #6
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    Sent u an email Ben

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    Would you still post some progress tune and scans for review here for our benefit?

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    Quote Originally Posted by Hondaeater View Post
    Would you still post some progress tune and scans for review here for our benefit?
    Absolutely.

    Here is what I found on another forum too that I would like to share.

    Disable closed loop at idle and part throttle by setting PE TPS vs. RPM to 0 from 0RPM to 1200RPM inclusive. This forces Pe mode at idle (and subsequently Open Loop) and ignores the O2’s
    Is he referring to the HOT and COLD tabs under Power Enrich>Throttle?
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.

  9. #9
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    Here is the rest of it:

    Big Cam (lots of overlap) tips, tricks and discussion:



    After I had my base airflow pretty well dialed in, fueling appropriate and timing where it should be and re-enabled my LTFT?s? it all went to hell. My fuel trims would just dump the max amount of fuel (+25); the motor would shudder, misfire and smell very rich with heavy soot on the exhaust openings. Keep in mind that positive fuel trims are dumped on top of your Power Enrichment at WOT as well and I certainly didn?t want all that extra fuel at WOT. I should have figured this however I didn?t realize it would be this bad. After refusing to believe just the overlap and the headers would cause this bad of a false lean condition (and subsequent maxed + fuel trims), I confirmed I had no air/exhaust leaks. Now I needed to find a way to keep my fueling stable during idle. I figured I had the choice of going full on Speed Density or do a Hybrid Open Loop approach. Here is what I did, as I chose the ?Hybrid Open Loop/Closed Loop? approach:



    With a big cam (lots of overlap) and long tube headers, O2 sensors (including widebands) are worthless at idle. I had two approaches that I tried. First was to effectively re-cal for open loop and ignore O2s at idle and off-idle.





    Disable closed loop at idle and part throttle by setting PE TPS vs. RPM to 0 from 0RPM to 1200RPM inclusive. This forces Pe mode at idle (and subsequently Open Loop) and ignores the O2?s[/b]



    Set Pe enrichment to 1.0 from 0RPM to 1200RPM inclusive. This ?prevents? any Pe mode fuel enrichment to occur.



    Set columns 68*F through 230*F in your OL F/A vs. Coolant Temp vs. Map to 1.00 (one) up to the Map value you saw during your idle scans. For me I have a 1.00 in all cells from column 68*F ? 230*F and 20-80 kPa inclusive. (HPT > Engine > Fuel Control > OL/CL > Open Loop > Eq Ratio).



    Set Pe enable to a value lower than what you see at idle (look at your previous idle scans), I set mine to 50kPa and see 75-76kPa at idle (HPT > Engine > Fuel Control > Power Enrichment > Power Enrichment Pe Enable tables). In the same group of tables, set the Delay RPM and Enable Torque to Zero. I also made sure there was no ?adders? adding fuel such as ?Add vs. ECT? and ?Add vs. IAT?. Doing all of this ensures you will actually be in Pe Mode and subsequently OL at idle.



    Disable STFT Open Loop (HPT > Engine > Fuel Control > OL/CL > Open Loop > STFT Open Loop).



    This is optional however did help me out for off idle transitions:

    Set Closed loop proportional O2 error to (left to right):

    0.06250 0.06250 0.06250 0.06250 0.06250 0.06250 0.06250 0.15479 0.18750 0.21484 0.24023 0.27002 0.27979



    Disable DTC codes P0131 and P0151 by setting the code to ?3- no error reported? and be sure to have the SES box checked. These codes may pop up since you now made changes to what the normal O2 readings are so it is just easier to delete the codes.



    Save the changes and Flash the PCM with the new settings.
    Last edited by Gripenfelter; 6 Days Ago at 08:51 PM.
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.

  10. #10
    Senior Tuner Ben Charles's Avatar
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    I would honestly run this setup OL and not even use 02 sensors.. dial in the fuel with a WB and will quality injectors will stay perfect

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  11. #11
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    Quote Originally Posted by Ben Charles View Post
    I would honestly run this setup OL and not even use 02 sensors.. dial in the fuel with a WB and will quality injectors will stay perfect
    You're probably right. Here is the latest tune and data logs. Less stumbling under load but car wants to stall more. I sent you an email Ben if you're able to help me with the tune.

    Anything else you guys think I should change?

    Not sure why the wideband isn't working. Might be a broken wire somewhere. Gauge works fine. I'll take a look tonight.

    It stumbles a bit when you first hit the gas and the wideband jumps to 17 but half a second later it's fine.
    Attached Files Attached Files
    Last edited by Gripenfelter; 5 Days Ago at 04:57 AM.
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.

  12. #12
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    I think it needs more base airflow.
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.

  13. #13
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    You need to get the IAC down to the 40-60 range. It's at 100-110 now. Open the TB blade a bit more.
    I agree 100% with what Ben said, OL SD tune is the way to go on this combo.

  14. #14
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    Quote Originally Posted by kevin87turbot View Post
    You need to get the IAC down to the 40-60 range. It's at 100-110 now. Open the TB blade a bit more.
    I agree 100% with what Ben said, OL SD tune is the way to go on this combo.
    I'm going to play with the TB tonight and open it slightly. This weekend I'm going to see what I can do to keep closed loop. Otherwise I'll go open loop.
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.

  15. #15
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    Cracked the TB screw open slightly. No more surging or stalling.

    Drove "ok" for 15 mins and then all of a sudden went pig rich with the AFR reading 8.8. I think I have a bad coil, plug, or wire. Not a tuning issue. I'll take a look this weekend.
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.

  16. #16
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    Quote Originally Posted by Ben Charles View Post
    I would honestly run this setup OL and not even use 02 sensors.. dial in the fuel with a WB and will quality injectors will stay perfect
    agreed this is far too much cam for narrow bands.
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  17. #17
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    This information is for educational purposes only, tune at your own risk. Now that's out of the way.
    You started driving before the operating temp came up, the results are inconclusive. Even at op temp it would engage stall saver and go into OL. If all the Channels from post list were reporting it would be easier to sort out.
    Focusing on idle scan, delete the Accelerator Pedal- it's a cable driven TB but add % for the Throttle position (SAE) keep the TPS volts too. Delete fuel tank level, Baro pressure, Knock retard ( not needed tuning the idle), and add those channels in the post for better resolution of what is going on.
    As mentioned the IAC count is too high and in tune the Effective area has been altered but the Idle IAC count is still too high 100-110 Not sure why they were changed, it's the last thing to do. You do not adjust the Effective area to lower the IAC count if that is what was done. There is a throttle stop under the cable driven TB that a setscrew is adjusted to lower the IAC count in Scanner when at operating temperature. You can watch the steps drop live as you adjust the screw but you may want to kill it for safety since the setscrew is hard to get to while running. You may want to start over (recommended) with factory Effective area steps and adjust your idle setscrew to get down to about </=40 steps like kevin87turbo mentioned.
    The O2 switching voltages are adjusted too but the airflow isn't sorted out yet to know if they are on target. The Mode can't be determined where to make those O2 adjustments with your airflow so far off and recommend setting O2 back to stock for now.
    How do you eat an elephant... 1 bite at a time.
    So much of the tune is adjusted yet the idle portion isn't sorted out and I have no idea what/how those changes are going to effect the idle calibration. I would start over because adjustments have probably been made to fix some issues (causing others) but they effect the airflow representation which is still way off and those issues may resolve themselves if the airflow was represented properly in the first place. Idle adaptives are altered.... too much to list.
    Would you post log of progress with the setscrew adjustment? I would tighten up the overspeed = -10* /underspeed +10* from +/-100rpm to +/-300rpm. You can use special functions in scanner to set an RPM and adjust for best vacuum to find what to set the idle spark in geatr table. It looks a little high. You may want to 0 out the ECT in spark correction table from 50* up it is pulling timing out and then over/ under is correcting for Idle Base RPM deviation at cooler temps. The engine loses torque with a cam and that table is reducing the timing that is needed to get the torque back.

    The injectors are 80lb/hr at (3 Bar) 43.5psi right? Using the VCM Editor in tools.. unit conversion I calculated current inj = 80 , current fuel psi 43.5 (do you know what your FP is or is it 58psi?) New FP 58psi = 92.xxlb/hr it looks like yours is scaled to 60.85 FP @ 94.62lb/hr? odd fuel pump psi number but if that is what you have. Everything matters.
    01 Trans Am 5.7M P01.hpt stock 01 TA file if you do not have your original.
    Last edited by Hondaeater; 4 Days Ago at 11:48 AM.

  18. #18
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    Thanks Hondaeater.

    I started over with the tune.

    I'll post the tune and log files later this week.

    I adjusted my throttle body screw and opened it 1/16 of a turn. No more stalling issues.

    A local shop is letting me use their dyno. So far with 21 degrees of timing it's at 575 rwhp. Should finish WOT runs on the dyno in the next day or so. Then go back to closed loop tuning.

    Mods: 427 Dart block. 245cc TFS trick flow heads ported by TEA. FAST 102 intake. 102 Throttle Body. 1 7/8" headers. 3" true duals. Tremex T56 Magnum (TR6060 in a T56 case) Moser 9" rear end.

    I'll post a video of the dyno and dyno sheets.
    2001 Pontiac Trans Am
    427 DART block.
    TEA ported Trick Flow 245 heads.
    244/256 cam
    698 hp 647 tq on engine dyno.