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Thread: Gen4 idle tuning guide

  1. #41
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    They aren't exactly the same but are mostly similar

  2. #42
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    This is a great thread thanks Mike for writing this up.

    So one quick question regarding timing...you have 20/22 degrees as a starting point, so what is optimal timing to start with? Does it vary between cam choices, l have a stock cam would i start there or is 20 deg for a larger cam? Just curious if that is a base lime for all or just your cam.
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    Quote Originally Posted by openwheel25 View Post
    This is a great thread. How do you get around the car running rich after you flash it? If I warm my car up and change the tune and flash it back it runs rich for 20 minutes. It would take me all day to make a few changes and then wait for the rich condition to go away.
    I just leave closed loop on and let the 02s compensate. Really just using the method to find airflow and spark anyway. Daves method works to reset the rich after flash i have confirmed that.

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    Quote Originally Posted by JBZ View Post
    This is a great thread thanks Mike for writing this up.

    So one quick question regarding timing...you have 20/22 degrees as a starting point, so what is optimal timing to start with? Does it vary between cam choices, l have a stock cam would i start there or is 20 deg for a larger cam? Just curious if that is a base lime for all or just your cam.
    I wouldnt even use this method for a stock cam. Id just use factory settings. You can add base timing and soften the spark correction if you want to smooth it out.

    I use 20 degrees or so for all mild cams. Ranging from -5 to +5 overlap. Bigger cams will be higher rpm and possibly higher spark but 20 just seems to work great. Go too high and you get an over reactive idle. Go to low and it will want to die.

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    Quote Originally Posted by Widebody06 View Post
    Dsteck posted EOIT calcs a couple years ago and while it didnt completely stop the raw gas smell for me it made a massive improvement. It probably helps that I'm now running 200 cpi cats but I did run catless for several months after using EOIT tweaks. You guys are light years ahead of my in tuning experience so I'm just putting this out there in the hope you havent already done it or discounted it as a fix.
    I presume this guide is for E38s as my E40 screens and options look different, correct?
    I see integral and proportional airflow in e40 so the concept is the same.

    The screens are from my e38 though. Same idea as e40 disable all adaptives and find correct airflow and spark then turn adaptives on and tweak as necessary

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    When i got my tune professionally done the tuner didnt touch Idle spark table at all and only upped the entire min air flow table by 7.9. It idles fine but the timing seems low 11 - 14 adv and it does have idle (off brake...letting it roll forward) bucking. Still trying to figure it out and thought this thread might be worth lookimg at, although i do realize it is dirrected at cammed cars...i guess that just the forums way of telling me i need a cam.
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  7. #47
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    Quote Originally Posted by JBZ View Post
    When i got my tune professionally done the tuner didnt touch Idle spark table at all and only upped the entire min air flow table by 7.9. It idles fine but the timing seems low 11 - 14 adv and it does have idle (off brake...letting it roll forward) bucking. Still trying to figure it out and thought this thread might be worth lookimg at, although i do realize it is dirrected at cammed cars...i guess that just the forums way of telling me i need a cam.
    Sure, you can fix that using the tips in this thread.

    I belive CTS-V base spark is 15 degrees, so that's probably already pretty optimized for a stock cam. Most tuners won't touch stock idle settings for stock cams, so I wouldn't fault him for that.

    Find my tune on page 1 and copy in the spark over/under speed tables for neutral and gear. See if that cures the bucking. That is the original problem that got me headed down this path of research anyway. I can't stand the bucking when coming off the brake. The key is you need to 0 the 16 rpm cells and let airflow correct in that range. Since there is more load on the engine while in gear, airflow does a fine job at correcting in that small range. This has the opposite effect on manual cars, because if you try to use airflow only to correct the -+16 rpm range, you get wild oscillations because of the lack of engine load, so I leave spark correction on in those cells.

    I always advocate doing one change at a time and retest. Also, always let the idle learn a bit after flashing new tunes when messing with the adaptives. A good 1-2 minutes at least each time.
    Last edited by BigMike42; 06-11-2016 at 03:03 PM.

  8. #48
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    Quote Originally Posted by BigMike42 View Post
    Sure, you can fix that using the tips in this thread.

    I belive CTS-V base spark is 15 degrees, so that's probably already pretty optimized for a stock cam. Most tuners won't touch stock idle settings for stock cams, so I wouldn't fault him for that.

    Find my tune on page 1 and copy in the spark over/under speed tables for neutral and gear. See if that cures the bucking. That is the original problem that got me headed down this path of research anyway. I can't stand the bucking when coming off the brake. The key is you need to 0 the 16 rpm cells and let airflow correct in that range. Since there is more load on the engine while in gear, airflow does a fine job at correcting in that small range. This has the opposite effect on manual cars, because if you try to use airflow only to correct the -+16 rpm range, you get wild oscillations because of the lack of engine load, so I leave spark correction on in those cells.

    I always advocate doing one change at a time and retest. Also, always let the idle learn a bit after flashing new tunes when messing with the adaptives. A good 1-2 minutes at least each time.
    Awesome...thanks for the advice ill give it a shot.
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  9. #49
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    yeah, not many pro tuners will take the time to really get idle just right--bumping up min air until it idles decent enough is easier and usually gets people by.

    And this is probably the most detailed thread on gen 4 idle tuning that there is--I'm not sure many people even knew how to do this until now

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    Yeah bumping up the idle airflow is the most common direction "tuners" go, but a lot of the time it's wrong thing to do. You always want to have as much ignition timing that you can, short of having a touchy or surging problem. I've seen logs where they have the idle timing running down in the single digits, or even into retarded numbers because they've added so much airflow. Most any engine isn't going to like that, it's not efficient and it causes too much heat.

    I would say 15 degrees is a minimum that I would shoot for. I run my stock cam LSA's closer to 30 degrees of idle timing and super lean also. It's more work to get the idle to not be too sensitive, but it results in TPS values in the 3's or 4's and the load percentages super low too. It makes for an extremely clean, crisp and cool running engine though. This goes for cold starts also, too many times guys just add airflow to fix a slow start or dies after starting. All that does is makes the ign timing go even more retarded. Cold engines like a lot of ignition timing, not less. When you have a system that uses airflow AND spark for rpm control, you really can't just add a bunch of one without it trying to take away the other. The way I like to setup idle is a lot of ignition timing and as little airflow and fuel as it will run ok on. Reduce any rpm sensitivity by letting the airflow side have VERY little control and let the ign timing do most of the trimming. With a lot of ignition advance, the engine will be less likely to stall or idle slow in the first place. When the engine is running efficiently like that, it's FAR less sensitive to loads. And also with all that advance, reducing the idle speed by the ECM retarding ignition timing is easy because it has so much range to move it in. This high ign timing, low airflow control authority setup, at least on mild or stock cams will net you logs showing very little rpm adjustments happening with even idle spark compensation. After all, if the engine is making enough power to overcome any transient loads, it should be able to idle consistently with NO throttle plate or ignition timing trimming. That was a lesson us old guys learned in the '80's when smogged up engines ran so horribly that they needed all kinds of idle speed controls just to keep things like the A/C compressor load from killing the engine. Once engines started actually making power again, you ended up with less idle problems.
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  11. #51
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    Good food for thought...guess there is no reason not to play around with it except time.
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  12. #52
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    Quote Originally Posted by gmtech16450yz View Post
    Yeah bumping up the idle airflow is the most common direction "tuners" go, but a lot of the time it's wrong thing to do. You always want to have as much ignition timing that you can, short of having a touchy or surging problem. I've seen logs where they have the idle timing running down in the single digits, or even into retarded numbers because they've added so much airflow. Most any engine isn't going to like that, it's not efficient and it causes too much heat.

    I would say 15 degrees is a minimum that I would shoot for. I run my stock cam LSA's closer to 30 degrees of idle timing and super lean also. It's more work to get the idle to not be too sensitive, but it results in TPS values in the 3's or 4's and the load percentages super low too. It makes for an extremely clean, crisp and cool running engine though. This goes for cold starts also, too many times guys just add airflow to fix a slow start or dies after starting. All that does is makes the ign timing go even more retarded. Cold engines like a lot of ignition timing, not less. When you have a system that uses airflow AND spark for rpm control, you really can't just add a bunch of one without it trying to take away the other. The way I like to setup idle is a lot of ignition timing and as little airflow and fuel as it will run ok on. Reduce any rpm sensitivity by letting the airflow side have VERY little control and let the ign timing do most of the trimming. With a lot of ignition advance, the engine will be less likely to stall or idle slow in the first place. When the engine is running efficiently like that, it's FAR less sensitive to loads. And also with all that advance, reducing the idle speed by the ECM retarding ignition timing is easy because it has so much range to move it in. This high ign timing, low airflow control authority setup, at least on mild or stock cams will net you logs showing very little rpm adjustments happening with even idle spark compensation. After all, if the engine is making enough power to overcome any transient loads, it should be able to idle consistently with NO throttle plate or ignition timing trimming. That was a lesson us old guys learned in the '80's when smogged up engines ran so horribly that they needed all kinds of idle speed controls just to keep things like the A/C compressor load from killing the engine. Once engines started actually making power again, you ended up with less idle problems.
    Very cool, thanks for the insight. I have never tried a ton of timing, I may just try that using the method I posted in the OP to see how it sounds. I hate lopey idle in a DD. I came to the same result for my startups...it likes timing. I can run stock base airflow now.

    Any advice on hot (lean) restarts? My IAT just gets obliterated with the engine off and the car lopes like crazy for the first 5 mins or so then the iat cools back down and it smooths down. My only idea was to turn closed loop on right away (no delay).
    Last edited by BigMike42; 06-11-2016 at 06:30 PM.

  13. #53
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    Quote Originally Posted by schpenxel View Post
    yeah, not many pro tuners will take the time to really get idle just right--bumping up min air until it idles decent enough is easier and usually gets people by.

    And this is probably the most detailed thread on gen 4 idle tuning that there is--I'm not sure many people even knew how to do this until now
    Yeah I didn't find much on it, but I knew right away after tuning my own car it wasn't the way to go. The original method I used was to lock in RPM at each break point, like 600, then 800, etc and try to find airflow based on the spark correction. But you just end up chasing your tail because the integral keeps catching up and trimming airflow, so it's a futile effort. Getting exact airflow at each break point is also over kill, I got smoothest results by just locking the airflow 1000 and lower. The tables are way over done from the factory.

  14. #54
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    So to recap.....just because I am retarted and easily confused.... The goal with setting base spark and min idle air, is to get min air down where it should be, with idle spark elevated to reduce the amount of correction spark needed. Correct? So....if base idle air and spark are optomised, under/over correction spark should not be called into the game to correct target idle rpm setpoint?

    Asuming I understand this, I should not need have base idle spark as low as it was before, to allow underspeed spark correction to control under speed?

    Currently, my idle is pretty good at 17 deg, but....I do see adaptive spark ramp up to 22 or so, and as low at 8. I know my min air is not optomised though, cause it's always been an excersise of raise/lower air experimentations and watching corrective spark, which I just used 17 deg because it sounded like a good number.

    I'm about to give this a whirl. I have my "idle cal" tune ready to flash and an idle layout built. Just lacking motivation.
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    Quote Originally Posted by Michael_D View Post
    So to recap.....just because I am retarted and easily confused.... The goal with setting base spark and min idle air, is to get min air down where it should be, with idle spark elevated to reduce the amount of correction spark needed. Correct? So....if base idle air and spark are optomised, under/over correction spark should not be called into the game to correct target idle rpm setpoint?

    Asuming I understand this, I should not need have base idle spark as low as it was before, to allow underspeed spark correction to control under speed?

    Currently, my idle is pretty good at 17 deg, but....I do see adaptive spark ramp up to 22 or so, and as low at 8. I know my min air is not optomised though, cause it's always been an excersise of raise/lower air experimentations and watching corrective spark, which I just used 17 deg because it sounded like a good number.

    I'm about to give this a whirl. I have my "idle cal" tune ready to flash and an idle layout built. Just lacking motivation.

    Yes, this method allows you run higher spark because your idle trimming should be very minimal. I still relax the over/under speed settings though, if the 32 cell gets hit in stock form, it will throw the idle off.

    If you have a 2008+ car, try using max idle area. The strategy doesn't change, but it's easier to lock the throttle in with max idle area. You max base airflow at 64 g/sec and set max idle area to 1.10% or so, then adjust up or down. If you use this method, you need to use the regular idle spark table, not the main spark table.

    You can either turn spark correction off and shoot for best RPM error or you can leave spark correction on and shoot for the TPS that gives you the same average spark as commanded (use stock spark correction tables if using this method)

    Then once you find the right TPS, use the method I outlined in OP to find the base airflow number that matches that TPS. Then turn back on all the correction tables (relaxed versions I posted in my tune on page 1). It's probably much quicker this way with max idle area TBH.


    Your idle will be a ton better after you use this method if you are seeing 8 degrees of timing from correction.
    Last edited by BigMike42; 06-11-2016 at 07:28 PM.

  16. #56
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    You still gotta disable the adaptive airflow like in the original post, but do this with the tables instead to find TPS (if your PCM has the setting). Only thing to leave stock is the overspeed/underspeed delay so it enters the idle flow (do not set to 409 secs)



    Last edited by BigMike42; 06-11-2016 at 07:36 PM.

  17. #57
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    Beware running too low of idle airflow. It will completely kill reserve torque. You don't want to do that.

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    I may try that later, but think I got it pretty close using your other method. RPM error is still pretty high, about 25 total with all the correction tables killed. Considering the cam, I think it's pretty good. 235/255 at fifty on a 113 lsa. I ended up moving idle min down 5% from where it was, and it seems like like 19 deg. It is holding at 850 rpm. Log attached.

    I'll fuss around with the correction table now....I'm sitting in the car as I type.

    6-11-16_idle cal-02.hpl
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    Quote Originally Posted by Michael_D View Post
    I may try that later, but think I got it pretty close using your other method. RPM error is still pretty high, about 25 total with all the correction tables killed. Considering the cam, I think it's pretty good. 235/255 at fifty on a 113 lsa. I ended up moving idle min down 5% from where it was, and it seems like like 19 deg. It is holding at 850 rpm. Log attached.

    I'll fuss around with the correction table now....I'm sitting in the car as I type.

    6-11-16_idle cal-02.hpl
    25 rpm error is excellent for that cam size with correction disabled.
    Last edited by BigMike42; 06-11-2016 at 08:26 PM.

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    Looks like your locked in TPS is 17.65%. I did notice when the RPMs oscillated above 100 rpms, the TPS did correct so there is some hardcoded min correction going on still. Just keep that in mind when logging. For really big cams, it may be impossible to lock TPS using this method so max idle air may be the only way in that case. Can you post your tune, I want to dig around to see if there is any other setting that may be causing this. Could be the follower tables. I do see a 0 MPH column.
    Last edited by BigMike42; 06-11-2016 at 08:26 PM.