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Thread: Idle - TPS Voltage Threshold

  1. #1
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    Idle - TPS Voltage Threshold

    I am reading conflicting information regarding the maximum TPS voltage required to remain within the "Idle" parameters and would really appreciate some clarity. Most state the threshold exists at .6 V, but I am not sure how to verify this... maybe log the Idle spark tables and see if it populates itself...? Mabe log STIT and LTIT?

    Currently my IAC counts are maxed out on a cold start with my TPS voltage set at 0.57 V at idle with a 65* F ambient conditions, and the IAC counts stay that way for a long time while warming-up the engine; Desired RPMs at the ECT/ambient temperature is 950 RPMs, and the RPMs gradually step down to 800 RPMs at operating temperature. Once the engine is at operating temperature (~180-190 *F), the IAC counts still only drop down to the high 100s. If I turn the throttle adjustment screw just a hair more, the voltage jumps to .59 V, but there isn't enough of an airflow gain with such a small adjustment to justify being that close to the threshold value IMO. I recall being able to really dial this in back when I had a HCI 5.7L setup, but I am running a 402ci motor now. FWIW, I am running the same intake and TB as before, and both setups had a catchcan.

    I am just trying my best to keep myself from having to alter the TB blade in order to receive more airflow so any advice would be greatly appreciated. I can post a log and the tune, but I am not sure this will necessarily help answer my basic question.

    Thanks!




    PS - Yes, I am followng the TPS reset procedure after every adjustment.

  2. #2
    Moderator mowton's Avatar
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    My understanding is you can go to 1.25V. That being said I try and stay at .8/.9 max and that is predicated on the size of the cam. If more is needed, then you have to open the hole drilled in the throttle blade. You should set the blade at about 40-60 counts with a cam at operating temperature. Stock is like 60-80....Now if you are running an LS2 throttle body (90 MM) then you need to move the IAC effective area table to compensate for the larger closed throttle area, but it sounds like you retained the stock 78mm so this doesnt apply. After you reset the set screw, unplug the TPS connector, key on for 20-30 seconds, key off, reattach connector and s/b good to go.

    Log the IAC counts, desired counts, IAC Desired Air, STIT, LTIT, MAF air, Dynamic air, advance etc to monitor your progress. Monitor the Fuel Trim Cell PID to make sure you are staying in the idle mode. Another good indicator is the timing is jumping about due to adaptive idle mode as well.

    Ed M
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  3. #3
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    Quote Originally Posted by mowton View Post
    My understanding is you can go to 1.25V. That being said I try and stay at .8/.9 max and that is predicated on the size of the cam [and flow through other sources of air supply post-TB, right? Ex. Catchcan]. If more is needed, then you have to open the hole drilled in the throttle blade. You should set the blade at about 40-60 counts with a cam at operating temperature. Stock is like 60-80....Now if you are running an LS2 throttle body (90 MM) then you need to move the IAC effective area table to compensate for the larger closed throttle area, but it sounds like you retained the stock 78mm so this doesnt apply. After you reset the set screw, unplug the TPS connector, key on for 20-30 seconds, key off, reattach connector and s/b good to go.

    Log the IAC counts, desired counts, IAC Desired Air, STIT, LTIT, MAF air, Dynamic air, advance etc to monitor your progress. Monitor the Fuel Trim Cell PID to make sure you are staying in the idle mode. Another good indicator is the timing is jumping about due to adaptive idle mode as well.

    Ed M
    See comment above.

    Thanks for the reply! I am not sure why people keep posting .6 V shouldn't be exceeded in order to remain in the Idle tables. It is good to know that you have been able to accomplish this at much higher TPS voltage values. Yes, I have always targeted sub-100 IAC counts during idle at operating temperatures since it allows sufficient room during cold starts through various seasons/much lower ambient temperatures. Yes, that is the same TPS reset procedure I always follow; thanks for clarifying.

    If forgot to mention - I am running a NW 102 TB (no hole in the TB blade, and I'd like to keep it that way ) with a FAST 102 TB on a 2004 GTO (DBC, not DBW). No MAF; CLSD w/only STFT.

    I wasn't aware there was a PID that stated it was in idle or not, but I do log the remainder of the parameters in addition to a PID that notifies me of OL/CL; maybe this is the "Fuel Trim Cell" and I don't recognize the name right now. The adaptive timing is definitely occurring since it does jump around a good bit; I am commanding 30*, and I have seen it go from high teens to 34-ish*.

    FWIW, the car still actually idles great, but it bothers me that the IAC doesn't have the room to "help" during a cold start. I will try raising the TPS voltage a bit more to give the IAC more room on the cold start then try to track whether it is in the idle mode or not. I will also log the RAF at this same time to see if it needs any further changes since I've only been through 1 iteration thus far.

    Thanks for the reply!

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    Something else worth noting is that while tuning the RAF, I noticed the LTIT cell was populated from the beginning even though I cleared out the fuel trims through the VCM controller. This value also didn't change throughout the entire idle tuning log. Weird.

    I haven't ever seen a straight answer for this - am I supposed to do anything with the STIT values that get populated in the log, or do I only just copy the desired airflow averages then paste them directly into the RAF within the tune? I've seen where some people add the STIT and LTIT together then add them to the logged desired airflow, and they will paste this new value to the RAF table within the tune. It just seems odd that you would take a fueling measurement and add it directly to an airflow measurement... then again, maybe I am misinterpreting what each is measuring.

    Nevermind, I am an idiot -

    http://www.ls1.com/forums/f9/tuning-...33/#post690564

    http://www.ls1.com/forums/f9/tuning-...33/#post690567
    Last edited by LaTechGTO; 05-06-2015 at 11:21 AM.

  5. #5
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    Ed M
    2004 Vette Coupe, LS2, MN6, Vararam, ARH/CATs, Ti's, 4:10, Trickflow 215, 30# SVO, Vette Doctors Cam, Fast 90/90, DD McLeod, DTE Brace, Hurst shifter, Bilsteins etc. 480/430

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    I just realized I actually had a copy of the config and the log file on my flash drive. Any idea on the lingering LTIT?

    IDLE-Airflow.cfg

    Idle Tuning 20150504.hpl

  7. #7
    Moderator mowton's Avatar
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    MAP is 180+ kPa??????

    Ed M

    Update -- got it figured out....new .cfg
    Last edited by mowton; 05-06-2015 at 04:38 PM.
    2004 Vette Coupe, LS2, MN6, Vararam, ARH/CATs, Ti's, 4:10, Trickflow 215, 30# SVO, Vette Doctors Cam, Fast 90/90, DD McLeod, DTE Brace, Hurst shifter, Bilsteins etc. 480/430

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  8. #8
    Moderator mowton's Avatar
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    Post your tune, with the 102 TB the IAC effective area table will need updating. Also add the TPS volts PID please to your .cfg

    Ed M
    Last edited by mowton; 05-06-2015 at 07:26 PM.
    2004 Vette Coupe, LS2, MN6, Vararam, ARH/CATs, Ti's, 4:10, Trickflow 215, 30# SVO, Vette Doctors Cam, Fast 90/90, DD McLeod, DTE Brace, Hurst shifter, Bilsteins etc. 480/430

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  9. #9
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    Quote Originally Posted by mowton View Post
    MAP is 180+ kPa??????

    Ed M

    Update -- got it figured out....new .cfg
    Good deal... You had me scratching my head there haha

    Quote Originally Posted by mowton View Post
    Post your tune, with the 102 TB the IAC effective area table will need updating. Also add the TPS voly PID please to your .cfg

    Ed M
    I'll post the tune here later when I get to a computer with internet. The IAC Steps vs Effective Area is same as a stock car. What's the advantage there? I've heard mixed comments about altering that table. FWIW, only the last few cells in the IAC Park Position have been modified as well.

  10. #10
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    Here is the log from the idle run I did today. I added the TPS Voltage to the config (as a reference in case it was overlooked earlier, the previous voltage was 0.57; I added the PID to this config before, but I must have forgot to save it). I am MUCH happier with the new IAC counts, and I lucked up and got it on the first try at adjusting the TB blade.

    I added the Fuel Trim Cell also, but even after doing some reading on the "20" cell, I am still not sure how this corresponds to telling whether the car is reading out of the idle cells.

    The last changes to the config file from before was that I made sure the Desired Airflow, LTITs, and STIT all had consistent units. I am not logging the STIT vs ECT in the histogram as well to make the addition easier.

    I still have questions:

    1) What might be causing the lingering value in the LTIT cell? I guess when I reset the trims in the VCM controls, it doesn't reset this number. The maximum value as noted in the tune is 3 g/s, and the scanner holds it at 1.67 g/s.

    2) The AFR seems a bit rich throughout the tune, even in CL. Should I go about adjusting the OLFA and VE tables? I might should recalibrate my WB again just to make sure. I've also heard the preloaded NGK AFX transfer function might be a shade off, but I've never had a quick enough eye to watch both the computer screen and the WB screen.

    3) If I add the Desired Airflow (positive number) to the STIT (negative numbers), it would make the overall value negative. How's this possible?

    At the end of the day, I really do think the car idles great, but the numbers don't align with what I feel like I am experiencing. If there is room for improvement, which I believe there is, I would like to reach that goal. I've attached the latest log and config file.

    Idle Tuning 20150506.hpl

    IDLE-Airflow.cfg

  11. #11
    Moderator mowton's Avatar
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    Quote Originally Posted by LaTechGTO;382331

    I added the Fuel Trim Cell also, but even after doing some reading on the "20" cell, I am still not sure how this corresponds to telling whether the car is reading out of the idle cells. [COLOR=#FF0000
    -- 20 is idle with EVAP Closed and 17 is Idle P/N AC off....
    [/COLOR]

    1) What might be causing the lingering value in the LTIT cell? I guess when I reset the trims in the VCM controls, it doesn't reset this number. The maximum value as noted in the tune is 3 g/s, and the scanner holds it at 1.67 g/s. -- Is it an automatic or a stick, the 17 says Auto. The 1.76 for IG wont change if you are in P/N. Now that LTIT is stuck at 0 so I will need to see the tune file to see what the limits are set to.


    2) The AFR seems a bit rich throughout the tune, even in CL. Should I go about adjusting the OLFA and VE tables? I might should recalibrate my WB again just to make sure. I've also heard the preloaded NGK AFX transfer function might be a shade off, but I've never had a quick enough eye to watch both the computer screen and the WB screen. -- It actually looks pretty good...I need to see the tune too see what stoich AFR has been set to, if 14.2 for E10, then it is good.

    3) If I add the Desired Airflow (positive number) to the STIT (negative numbers), it would make the overall value negative. How's this possible? -- You dont add Desired to the STIT, the Desired Airflow is the combination of all airflow adders to arrive at a required airflow, you start with the basel idle Air (RAF, BRAF etc) and then you add items like the LTIT, STIT, FAN Airflow, Cracker, Follower etc. By turning off the Fans, no follower/cracker (not moving the car or throtle blade) your LTIT+STIT becomes the error correction values for the BAse idle air table. You set up a histogram at the temperature breaks and then copy/paste add to the RAF table. That will bring your STIT and LTIT closer to 0, I like to get about -.2 or so. takes several passes at it.

    At the end of the day, I really do think the car idles great, but the numbers don't align with what I feel like I am experiencing. If there is room for improvement, which I believe there is, I would like to reach that goal. I've attached the latest log and config file.

    Idle Tuning 20150506.hpl

    IDLE-Airflow.cfg
    Ed M
    Last edited by mowton; 05-06-2015 at 10:41 PM.
    2004 Vette Coupe, LS2, MN6, Vararam, ARH/CATs, Ti's, 4:10, Trickflow 215, 30# SVO, Vette Doctors Cam, Fast 90/90, DD McLeod, DTE Brace, Hurst shifter, Bilsteins etc. 480/430

    ERM Performance Tuning -- Interactive Learning ..from tuning software training to custom tunes
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    Sorry, after all the running around yesterday, I forgot to post the tune file. I've attached the latest tune I've uploaded AFTER I applied the RAF numbers from the first log I posted. I feel like I might have taken a step in the wrong direction after the log I ran and posted yesterday so I haven't processed that data yet.

    Most Recently Loaded Tune.hpt

    I'll respond to your post once I get to work and settled in.

    Thanks again!

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    I added the Fuel Trim Cell also, but even after doing some reading on the "20" cell, I am still not sure how this corresponds to telling whether the car is reading out of the idle cells.

    -- 20 is idle with EVAP Closed and 17 is Idle P/N AC off....

    Thanks! I promise I searched and searched for that information yesterday, and the only information I could really find for it was in this link, which didn't do me much good:http://www.hptuners.com/help/vcm_edi...dvanced_ve.htm

    After a litte more time searching this morning from a computer instead of my phone, I found this link (Page 3): http://ls1tuningguide.com/tuningmanu...structions.pdf MUCH BETTER DESCRIPTIONS!

    Seeing that I am remaining within the idle parameters completely goes against all of the comments surrounding .6 V being the voltage threshold - Thanks for that nugget of information! Now what's werid is that it doens't state whether it is In Gear or P/N... just that EVAP is closed. EVAP is disconnected and removed so I'd hope it is showing "closed" haha. Up until now since I wasn't sure if it would recognize my PNP switch so I have just been populating my P/N and In Gear cells the same since the other tuning conditions will require even more airflow (Ex. AC On). The Fuel Trim Cell doesn't really tell me what's going on as far as In Gear or PN, but since it is populating the In Gear STIT (IIRC), I would think that information is out there somewhere. I think I entered a PID the other day to track gear position, and IIRC, it just read D2 in all gears. Not sure if I did it right though. I am also thinking the PRNDL has to be active in the tune for it to read whether it is in gear or not. I experienced some weird issues when I tried to activate PRNDL then re-write the tune.




    1) What might be causing the lingering value in the LTIT cell? I guess when I reset the trims in the VCM controls, it doesn't reset this number. The maximum value as noted in the tune is 3 g/s, and the scanner holds it at 1.67 g/s.

    -- Is it an automatic or a stick, the 17 says Auto. The 1.76 for IG wont change if you are in P/N. Now that LTIT is stuck at 0 so I will need to see the tune file to see what the limits are set to.

    The car was originally a manual, but I have rewired the ECU while adding the 4L80E connector and PNP connector/switch. I will have to look at the log file again, but I thought it was reading STIT IG (as I mentioned earlier, I am not sure any more) so I was wondering why it wouldn't change the LTIT IG values. Apparently I need some sleep because all of this information is running together. I've been wondering if there was a way to reset the STIT and LTIT values without just writing a new calibration... kind of like how fuel trims are reset.



    2) The AFR seems a bit rich throughout the tune, even in CL. Should I go about adjusting the OLFA and VE tables? I might should recalibrate my WB again just to make sure. I've also heard the preloaded NGK AFX transfer function might be a shade off, but I've never had a quick enough eye to watch both the computer screen and the WB screen.

    -- It actually looks pretty good...I need to see the tune too see what stoich AFR has been set to, if 14.2 for E10, then it is good.

    IIRC, stoich is set at the standard 14.68 in the tune file (there are values in the tune for flex fuel, but it's not truly active on the car), which is what's being displayed in the table as Commanded AFR once hits the OLFA table values of 1 and also during CL. I am pretty sure I have this in the tune since I am also recording Err%. The NBs don't focus on Lamba = 1, do they?



    3) If I add the Desired Airflow (positive number) to the STIT (negative numbers), it would make the overall value negative. How's this possible?

    -- You dont add Desired to the STIT, the Desired Airflow is the combination of all airflow adders to arrive at a required airflow, you start with the basel idle Air (RAF, BRAF etc) and then you add items like the LTIT, STIT, FAN Airflow, Cracker, Follower etc. By turning off the Fans, no follower/cracker (not moving the car or throtle blade) your LTIT+STIT becomes the error correction values for the BAse idle air table. You set up a histogram at the temperature breaks and then copy/paste add to the RAF table. That will bring your STIT and LTIT closer to 0, I like to get about -.2 or so. takes several passes at it.

    UGH! If only I had paid attention this part out of the link in my post yesterday - "The base airflow consists of the sum of the following individual components:" and "Desired Idle Airflow The net result is that the PCM takes the Base Idle Airflow (including LTIT) and then adds the STIT to come up with a final Desired Idle Airflow (which generally is available as a PID for logging)." I didn't realize it was already doing the calculation in the background. I have forgotten so much in the last few years of not tuning at all. Luckily I have only been taking the desired airflow and pasting it into the RAF table directly, but for some reason, my STITs have went in the opposite direction. The first log file basically told me I needed more RAF, and the second log file told me that I needed to remove almost double the original amount I added. Again, I will have to look at this information again to make extra sure since I have been uber-busy lately.
    Thanks again for taking the time to discuss through all of this information with me! I am really trying extra hard to absorb it all.

  14. #14
    Also fyi, fuel trim clear will not clear out the LTITs, doing a write entire will clear them to be able to get an accurate scan. Helps to make sure the car starts consistent cold, hot, even after battery has been unplugged.

  15. #15
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    Quote Originally Posted by xrelapse13 View Post
    Also fyi, fuel trim clear will not clear out the LTITs, doing a write entire will clear them to be able to get an accurate scan. Helps to make sure the car starts consistent cold, hot, even after battery has been unplugged.
    Yeah, I didn't see any result from the fuel trim reset function. I also wrote a fresh calibration before each log, yet it still displayed a LTIT value so it has to be something within the tune itself. FWIW, I also performed a couple of ignition cycles after the fresh calibration. I definitely try to make sure it starts/idles great in all conditions; I am starting to have flashbacks to when I tuned this car while it was just a manual H/C/I 5.7L and battled numerous idle issues.

    Thanks for the input!

  16. #16
    Moderator mowton's Avatar
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    Quote Originally Posted by LaTechGTO View Post
    Yeah, I didn't see any result from the fuel trim reset function. I also wrote a fresh calibration before each log, yet it still displayed a LTIT value so it has to be something within the tune itself. FWIW, I also performed a couple of ignition cycles after the fresh calibration. I definitely try to make sure it starts/idles great in all conditions; I am starting to have flashbacks to when I tuned this car while it was just a manual H/C/I 5.7L and battled numerous idle issues.

    Thanks for the input!
    In the Adaptive Idle Airflow tables you can set the learning limits (plus and minus) for each of the LTIT functions. Setting it to 0 will clear it. In order for them to move you need to set a value like .5 or 1.0.....stock is usually +.5 and -3.0 IIRC.

    Ed M
    2004 Vette Coupe, LS2, MN6, Vararam, ARH/CATs, Ti's, 4:10, Trickflow 215, 30# SVO, Vette Doctors Cam, Fast 90/90, DD McLeod, DTE Brace, Hurst shifter, Bilsteins etc. 480/430

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  17. #17
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    Quote Originally Posted by mowton View Post
    In the Adaptive Idle Airflow tables you can set the learning limits (plus and minus) for each of the LTIT functions. Setting it to 0 will clear it. In order for them to move you need to set a value like .5 or 1.0.....stock is usually +.5 and -3.0 IIRC.

    Ed M
    I can't view my tune right now, but I think the range is set for 0-3 g/sec. I don't think setting it to zero then back to a value (say, 3) will clear it; it will just make the LTIT non-existant while it's set to 0, right? I think it is still weird that I am unable to clear the stored LTIT value since it is derived from a collection of STITs. Oh well, I am going to update the tune from the values I logged yesterday and try another iteration of tuning the idle.

  18. #18
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    I figured I would close the loop on this discussion in case someone else is going through something similar and can see what the results were. There is no telling how many threads I read and never saw a definitive result. Cliffs: I entered the values from the most recently posted log - 1) she idled like a charm; maybe even more stable than before 2) IAC counts are now almost exactly 45 at operating conditions and 40 210*F ECT. 3) STIT have are +/- 1 g/sec (I think they might actually be a bit less).


    I added the Fuel Trim Cell also, but even after doing some reading on the "20" cell, I am still not sure how this corresponds to telling whether the car is reading out of the idle cells.

    -- 20 is idle with EVAP Closed and 17 is Idle P/N AC off....

    Thanks! I promise I searched and searched for that information yesterday, and the only information I could really find for it was in this link, which didn't do me much good:http://www.hptuners.com/help/vcm_edi...dvanced_ve.htm

    After a little more time searching this morning from a computer instead of my phone, I found this link (Page 3): http://ls1tuningguide.com/tuningmanu...structions.pdf MUCH BETTER DESCRIPTIONS!

    Seeing that I am remaining within the idle parameters completely goes against all of the comments surrounding .6 V being the voltage threshold - Thanks for that nugget of information! Now what's werid is that it doesn’t state whether it is In Gear or P/N... just that EVAP is closed. EVAP is disconnected and removed so I'd hope it is showing "closed" haha. Up until now since I wasn't sure if it would recognize my PNP switch so I have just been populating my P/N and In Gear cells the same since the other tuning conditions will require even more airflow (Ex. AC On). The Fuel Trim Cell doesn't really tell me what's going on as far as In Gear or PN, but since it is populating the In Gear STIT (IIRC), I would think that information is out there somewhere. I think I entered a PID the other day to track gear position, and IIRC, it just read D2 in all gears. Not sure if I did it right though. I am also thinking the PRNDL has to be active in the tune for it to read whether it is in gear or not. I experienced some weird issues when I tried to activate PRNDL then re-write the tune.

    After looking back at my log files, I am thinking the reason cell 20 doesn’t state In Gear or P/N is because it is still in OL and doesn’t care. It switches to cell 17 a short time after going into CL, as stated before means that it is in Idle P/N (AC off). I enabled PRNDL in my tune yesterday, but it doesn't seem to be reading my PNP Switch or I’m not using the right PID to track it (I’ve tried Gear Position and PRNDL); Most likely the latter since it recognizes P/N during the idle tuning due to cell 20 being active. No biggie, IMO... More tinkering on this later.



    1) What might be causing the lingering value in the LTIT cell? I guess when I reset the trims in the VCM controls, it doesn't reset this number. The maximum value as noted in the tune is 3 g/s, and the scanner holds it at 1.67 g/s.

    -- Is it an automatic or a stick, the 17 says Auto. The 1.76 for IG wont change if you are in P/N. Now that LTIT is stuck at 0 so I will need to see the tune file to see what the limits are set to.

    The car was originally a manual, but I have rewired the ECU while adding the 4L80E connector and PNP connector/switch. I will have to look at the log file again, but I thought it was reading STIT IG (as I mentioned earlier, I am not sure any more) so I was wondering why it wouldn't change the LTIT IG values. Apparently I need some sleep because all of this information is running together. I've been wondering if there was a way to reset the STIT and LTIT values without just writing a new calibration... kind of like how fuel trims are reset.

    As stated before, rewriting a new calibration won’t clear the LTIT. I am guessing this will eventually clear up once I drive around some since I’ve tuned the idle some now.



    2) The AFR seems a bit rich throughout the tune, even in CL. Should I go about adjusting the OLFA and VE tables? I might should recalibrate my WB again just to make sure. I've also heard the preloaded NGK AFX transfer function might be a shade off, but I've never had a quick enough eye to watch both the computer screen and the WB screen.

    -- It actually looks pretty good...I need to see the tune too see what stoich AFR has been set to, if 14.2 for E10, then it is good.

    IIRC, stoich is set at the standard 14.68 in the tune file (there are values in the tune for flex fuel, but it's not truly active on the car), which is what's being displayed in the table as Commanded AFR once hits the OLFA table values of 1 and also during CL. I am pretty sure I have this in the tune since I am also recording Err%. The NBs don't focus on Lamba = 1, do they?

    I am going to recalibrate my AFR sensor, but I am not really worried about such a small difference right now (AFR Err% = 1-3%; not sure this is even “real”) since it idles great.



    3) If I add the Desired Airflow (positive number) to the STIT (negative numbers), it would make the overall value negative. How's this possible?

    -- You dont add Desired to the STIT, the Desired Airflow is the combination of all airflow adders to arrive at a required airflow, you start with the basel idle Air (RAF, BRAF etc) and then you add items like the LTIT, STIT, FAN Airflow, Cracker, Follower etc. By turning off the Fans, no follower/cracker (not moving the car or throtle blade) your LTIT+STIT becomes the error correction values for the BAse idle air table. You set up a histogram at the temperature breaks and then copy/paste add to the RAF table. That will bring your STIT and LTIT closer to 0, I like to get about -.2 or so. takes several passes at it.

    UGH! If only I had paid attention this part out of the link in my post yesterday - "The base airflow consists of the sum of the following individual components:" and "Desired Idle Airflow The net result is that the PCM takes the Base Idle Airflow (including LTIT) and then adds the STIT to come up with a final Desired Idle Airflow (which generally is available as a PID for logging)." I didn't realize it was already doing the calculation in the background. I have forgotten so much in the last few years of not tuning at all. Luckily I have only been taking the desired airflow and pasting it into the RAF table directly, but for some reason, my STITs have went in the opposite direction. The first log file basically told me I needed more RAF, and the second log file told me that I needed to remove almost double the original amount I added. Again, I will have to look at this information again to make extra sure since I have been uber-busy lately.

    I obviously got mixed up in the terminology, but the moral of the story is to just focus on desired airflow in the log then copy/paste the information from the log into the airflow table within the tune. Done. I think I started getting nervous since my values didn’t seem correct since they were substantially lower than my previous Base Idle Airflow values in my tune… but I must have forgotten that I opened the TB blade more between the first and second log to get my IAC counts lower so it doesn’t suffer on a fresh start in colder temperatures.

    Thanks againg for all of the input from everyone, and espeically for mowton for having patience with me

  19. #19
    Moderator mowton's Avatar
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    Glad it all fell into place. Alot of people are leary of IAC tuning but once you have done it a few times it becomes intuitive. The remaining IAC tuning will come from coast down which is where the IAC effective area table will come more into play. At stop, adaptive idle does a great job keeping you within your desired idle rpm setting.

    Thanks for the props as well...

    Ed M
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  20. #20
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    Quote Originally Posted by mowton View Post
    Glad it all fell into place. Alot of people are leary of IAC tuning but once you have done it a few times it becomes intuitive. The remaining IAC tuning will come from coast down which is where the IAC effective area table will come more into play. At stop, adaptive idle does a great job keeping you within your desired idle rpm setting.

    Thanks for the props as well...

    Ed M
    Thanks! Yeah, it is definitely much easier than I thought; As you have probably noticed, I have a nasty habit of overcomplicating things haha. I think the biggest things for me was keeping the nomenclature and roles for each item - realizing a lot of different values are treated as adders to make up the Base Idle Airflow, and that the logged Desired Idle Airflow accounts for all of these and should be pasted directly into the Base Running Airflow table in order to account for the adjustments being made by the STIT and LTIT, ultimately resulting in close-to-zero STIT and LTIT. From what I am seeing, the Desired Airflow only correlates to the desired airflow through the IAC, not for the engine - this was another point of confusion to me early on.

    Is there a target STIT value? I see most people like to run negative STITs as long as it doesn't cause any forms of "cruise control" becuase it ensures the engine is getting plenty of air between throttle transitions instead of stumbling/hunting for idle. Then again, I would think it would be best to have this as close to 0 as possible (negative or positive, no difference) since there are other tables that can be modified to aid in the previous idle issue scenario.

    I am still not sure how to adjust for the IAC effective area, and the reading I have done surrounding this topic basically suggests a few things 1) the IAC hole in the TB is much smaller on aftermarket TBs, necessitating either a change in the effective area vs IAC steps or by modifying the hole to allow easier airflow to the IAC 2) getting the IAC counts as low as possible since it seems to be much more accurate in the lower flow scenarios 3.) the changes being made are more of guess work than science. I think the ultimate reason for this is to make the dynamic flow match the anticipated flow, correct? I don't think I said that right, but basically for the IAC steps (anticipated area by IAC position = certain amount of airflow) to correlate to the actual flow going through it, which alows easy, mythodical adjustment later for idle tuning while moving.

    I am still hung up wondering if the NBs are actually adjusting for the anticipated stoich for the E10 fuel. I was always under the impression they targeted the stoich saved in the tune, not lambda = 1 for the fuel being used. In my mind, this would remove the need for a flex fuel sensor unless in OL. Maybe they do target Lamba = 1 for all different types of fuel while in CL (within the window for the NBs), hence the seemingly rich state I was noticing on the WB readings.

    Also, for those that are reading, I stated something earlier about "In Gear STIT" - There isn't such a thing; STIT doesn't care if you are In Gear or in P/N; only LTITs care since the values for each could be very different.

    Thought I was done, didn't you? LOL