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Thread: E38 idle tuning

  1. #1
    Lifetime Member hymey's Avatar
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    Thumbs up E38 idle tuning

    THIS THREAD OUTLINES E38 IDLE TUNING AND ADJUSTMENTS. PLEASE READ THROUGH ALL FOR INFO IN DETAIL OR PLEASE SKIP TO POST 25 FOR A FASTER SIMPLIFIED VERSION




    While the challenge has always lied in perfecting the VVE table I have found getting the perfect idle more challenging. My car has a 218 224 112 cam which is relatively small compared to some setups. It sounds good at idle but to be honest my old 308-LJ idled better with a crane 288 solid cam and 750DP Holley.

    While you can get a e38 controlled engine idling well getting them idling very good is more challenging. I have been experimenting a lot getting a decent idle with no hunting, basically the engine idles like stock now with a deep note and I have pulled 10% fuel out as so much was passing through before.

    Basically I zero out the airflow correction tables B1845 and B1843. Then use B1829 to adjust throttle percentage at idle. If airflow and TP is correct we dont need much correction. So increasing or decreasing g/s values in b1829 will adjust TP to where you need it for correct idle speed. During this time there will be timing correction taking place keep a close eye on it and use this to help verify if it has to little or to much timing.

    You will find at this stage idle is dead smooth if it is not keep working at B1829 to get a decent idle.

    B1845 is proportional correction and integral is 1843. Proportional changes are direct adjustments to airflow where integral is a sum of these adjustments. Basically short and long term corrections. I disable B1843 by leaving the tables zeroed out as I previously mentioned. I then build a new table with b1845, this will ensure a dead smooth idle. But one thing. I put in the value -2.00 to all the cells in this table and it consistently reduced TP by around 2.8%, this verifys how much TP it takes away, If you look at the factory table rpms less then commanded idle have negative corrections and rpms above commanded idle have positive correction. I first set mine up like this and it hunted badly. It is ass about. Negative numbers reduce TP so they must be added in the cells adjacent to rpms above commanded idle. I tested this myself and now it works correctly which solves the hunting problem. Once I got this far I zeroed out the under and over timing correction tables and used bidi controls to raise and lower timing to find a happy medium, then re-established the timing correction tables.

    cheers

    Joel
    Last edited by hymey; January 18th, 2010 at 02:42 PM.

  2. #2
    Lifetime Member hymey's Avatar
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    attachment

    b1845 modded is how mine is setup,

    the other is factory
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  3. #3
    Senior Member alian's Avatar
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    Quote Originally Posted by hymey View Post
    attachment

    b1845 modded is how mine is setup,

    the other is factory
    Did you ever get it on the rollers Joel. I will save this post 4 when i do my cam next year. Ian

  4. #4
    Lifetime Member hymey's Avatar
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    Yeah its been on twice now Ian, first time It was wheelspinning tyres arent the best needed strapping right, second time with mafless tune in(sorted) the clutch slipped under load in 4th, It appears though it is making a lot more torque then the 226/232/114 cam made, Should make equivalent peak power and tonnes more area under the curve with 700nm plus torque at the wheels. A good mafless tune with correct fueling throughout the rev range has what has made the difference with this cam as it shines in the bottom and mid and revs quickly to 6600rpm..

    I have done some more experimenting with idle tuning today, This time zeroing b1845 and 43 everywhere and focusing on getting the TP correct. I found it is less likely to hunt as while the etb reacts quickly to idle correction it upsets idle just as fast which is why it takes a little time to get it right. Most logs I have seen of cammed e38s show airflow and timing are both being over corrected to compensate one another and starting from scratch is the best way to do it.

    After zeroing b1845 and 1843 I used minimum idle airflow and b1651 max idle area to adjust the tune in open loop. I found sometimes that TP% would vary by upto 2% at idle even though the learning tables were zeroed. Lowering B1651 and increasing B1845 prevents any movement in TP%.

    18.8% TP is the max TP% (using ETC.TP pid this is approx 12%) is the maximum allowed throttle area with stock B1651 settings, basically it's a maximum idle airflow, standard is 1.8, Mine is now 1.1 which maximum TP is 16.9%. By increasing minimum idle airflow it has prevented the TB dipping to around 13-14%. I have steadily increased minimum airflow and decreased maximum area to obtain a steady TB position. It doesnt take long to do within a few flashes I had it where I wanted but what I have learnt is that using these tables allows for total control of idle quality, Now idle sounds great with a slight chop absolutely no hunting and drives much smoother from dead still, showing the e38s true ability and tuning big cammed cars with no surging or hunting.
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    Last edited by hymey; December 28th, 2008 at 11:06 PM.

  5. #5
    Lifetime Member hymey's Avatar
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    The tables above show before and after adjustments. My car is a manual so the B1652 table can also be used for auto tranny cars. In my case Mine is manual so I have made B1651 and B1652 the same. Lowering these tables definately works and manipulating both B1651 and min. idle airflow is the key for total control of airflow at idle.

    cheers

    Joel
    Last edited by hymey; December 28th, 2008 at 11:07 PM.

  6. #6
    Joe (Moderator) joecar's Avatar
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    Ha Ha, LJ with a 308, a "beast"... cool...

  7. #7
    Lifetime Member swingtan's Avatar
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    OK, I've done some idle tests and spoken with Joel about this. Here's what I've found.

    Note: in my OS I do not have B1843, instead I have B1844

    B1844: Idle Integral Step Size.
    Integral:
    essential
    vital
    important
    basic
    fundamental
    primary
    central

    B1845: Idle Proportional Step Size.
    Proportional:
    relative
    comparative

    Setting both to "0" in all cells resulted in a steady idle, but it would "hang" like a stuck throttle. "Blipping" the throttle would allow the idle speed to drop to commanded, but a gentle rev would bring back the hang. Commanded TPS% ( TAC_PCT ) was 5.1% when idling correctly, but would go as high as 11.8% when hanging. While the idle was hanging, there was some hunting, as the spark timing tried to correct for the high RPM and ended up pulling too much timing. At 11.8% TP, commanded spark was -8.0' while the idle table was set to 13'. Blipping the throttle to return commanded TPS to 5% saw commanded spark at 13'.

    Setting Proportional Step Size ( B1845 ) to corse settings, made little change in the conditions above. Idle would still hang and could be corrected with a blip. Tested removing idle spark control and found it would start hunting badly to the point it almost stalled. The corse settings were as follows.

    Idle Normal
    RPM Idle
    Error
    -256 -1.500000
    -224 -1.500000
    -192 -1.000000
    -160 -1.000000
    -128 -0.500000
    -96 -0.500000
    -64 0.000000
    -32 0.000000
    0 0.000000
    32 0.000000
    64 0.000000
    96 0.500000
    128 0.500000
    160 1.000000
    192 1.000000
    224 1.500000
    256 1.500000


    Setting Proportional Step Size to a linear fill, from "0" to -1.5 and +1.5 ( which is close to stock settings )reduced the hang effects slightly, but it would still hang. The fans turning on had nill effect on idle quality at all though. Removing idle spark control again resulted in bad hunting.

    Setting Integral Step Size ( B1844 ) to corse settings resulted in a marked improvement, but still a slight hang. Idle was very steady and the hang could be fixed with a blip. Removing idle spark control resulted in minor hunting, but it was controlled compared with the previous test. When the cooling fans turned on while idle spark control was of, hunting got worse, but ws still controlled. When the fans turned off, the hunting all but went. The corse settings were as follows...

    LABELS Idle Mode
    Idle Normal
    RPM Idle
    Error
    -512 0.035156
    -480 0.035156
    -448 0.030273
    -416 0.030273
    -384 0.025391
    -352 0.025391
    -320 0.019531
    -288 0.019531
    -256 0.014648
    -224 0.014648
    -192 0.009766
    -160 0.009766
    -128 0.004883
    -96 0.004883
    -64 0.000000
    -32 0.000000
    0 0.000000
    32 0.000000
    64 0.000000
    96 0.004883
    128 0.004883
    160 0.009766
    192 0.009766
    224 0.014648
    256 0.014648
    288 0.019531
    320 0.019531
    352 0.025391
    384 0.025391
    416 0.030273
    448 0.030273
    480 0.035156
    512 0.035156

    Setting Integral Step Size to a linear fill from "0" to "0.035" ( each side of the "0" rpm axis ) saw no hang at all. Idle was very smooth and controlled very well. You could see the ECM command a little more air when the fans kicked in, but idle remained rock steady. Removing idle spark control now saw hunting get a little worse and when the fans kicked in with no spark control, it would get runaway and almost stall. This probably indicates that the ECM is over correcting with these values.

    What's the difference?

    The Integral step size seems to be the "primary" or "base" adjuster for idle air. The Proportional step size seems to have a limited effect, at least in the basic tests done. The descriptions in EFILive simply don't explain the tables in a clear enough way.

    How I would use these: I'd probably try zero-ing the proportional tables and then set the Integral tables to get the smoothest idle when "idle spark control" is disabled via the BiDi controls. Then reset the Proportional tables to stock ( possibly -10% ) and re-enable the "idle spark control". I really need to work out what the Proportional table acctually does and when it comes into play. The thing is, that this is the oposite to what Joel was seeing. Perhaps it's an OS difference, or just due to the cam. The main thing is, more work in needed.

    Logs of the idle tests are attached.

    Simon.
    Attached Files Attached Files

  8. #8
    Lifetime Member Chuck CoW's Avatar
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    Default Good work!

    Good work guys! I'm gonna play with this.

    Chuck CoW
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  9. #9
    Senior Member alian's Avatar
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    Joel and Simon, both of u r damn ledgendry with the e38s. helps the not so smart out here havn a go.
    Cheers Ian.

  10. #10
    EFILive Reseller ringram's Avatar
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    The key for me was min idle airflow and VVE for startup.
    If you readup on PID systems.
    Proportional is like you say direct adjustment, integral is the average over time and derrivative is the rate of change.
    When you change a system often its recommended to disable the derrivative. We have no access in the software yet to this. Also they say to reduce the proportional and increase the integral.
    This is what I have done and after startup mine is pretty good.
    In my book the less you can change the stock tune the better as all tables are interrelated, so ideally you set the right airflow and spark and the rest takes care of itself.

    Im going to take a look at the tables you guys mention anyway

    Ive been tuning a 440 cube LS7 in a HSV-R8 with 23x/23x cam.
    Get EFILive in europe (http://www.efilive.eu).
    2007 Escalade ESV L92 6.2L VVT.
    2014 VF SV LS3 Maloo.

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