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Thread: light throttle surge.

  1. #1
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    Default light throttle surge.

    I am trying to get rid of some surging / bucking that occurs at light throttle between 1000 and about 1800 rpm, if you apply more throttle or back off completely it goes away.

    It happens when the engine is hot or cold, I've looked around at suggestions, such as too much air flow or too little, playing with timing, but as I'm new to tuning I don't know much about what I'm doing and I can't seem to work it out, nothing seems to change it.

    Could anyone check out my tune and see if you could offer any tips or guidance.

    It would be much appreciated, thanks.

    Specs are:

    year 2005
    Ls1 5.7
    ported stock heads
    4>1 long tube headers
    2.5 dual exhaust with high flow cats
    ORCAI
    3.9 gears
    M6
    230/230 110 comp cam
    electronic throttle stock.
    no MAF.
    Attached Files Attached Files

  2. #2
    Joe (Moderator) joecar's Avatar
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    Default General quaestions/observations...

    What vehicle is it...?

    What is providing boost...?

    The trans segment is from an A4...?

    Are you seeing DTC P0102...?

    PE could be a little richer if NA (say EQ 1.16), or even more richer if boosted.

  3. #3
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    Quote Originally Posted by joecar View Post
    What vehicle is it...?

    What is providing boost...?

    The trans segment is from an A4...?

    Are you seeing DTC P0102...?

    PE could be a little richer if NA (say EQ 1.16), or even more richer if boosted.
    Thanks for your reply

    Holden VZ 2005

    Not sure what you mean by boost.

    Thanks for pointing that out, the original tune was done by a "professional" tuner, but there have been so many issues with it, no wonder they didn't want to unlock it. Would having the A4 segment in there be causing many issues, or should I change it to an M6?

    Yes P0102 is showing up.

    Ok I will have a look at the PE.

  4. #4
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    the trick to getting a cammed LS1/2/3 to idle and low speed rolling , and there a LOT of them, is a big subject to cover. Read up on the idle tuning stickys and related topics first so you have a good grasp of what to change and most importantly why to change.
    However, the first thing I noticed in your tune is the throttle cracker B4309 had been zeroed out. This can be best described as " the throttle blade resting position on overrun while still rolling"
    Clearly set to zero gives no extra opening from the "idle airflow stationery" point with which the engine needs to maintain a slow roll say at 5 to 10km/hr. Download a standard VZ tune from the Holden repository and copy over the table as a starting point. It will be miles out but give you a starting point to work from.....Log a slow roll and track the cell in this table.. usually the more cracker you give it the more it will roll on with no foot throttle, too much and you get auto cruise, not enough and you get the light throttle surge happening.
    The second glaring problem is the issue of timing.
    Low speed roll and idle in a cammed engine are highly affected by timing.
    With B5917 set to 412km/hr and B5916 set to 1.19 this means when the throttle is closed and at any speed you are using the base spark in gear table for rolling idle. As you can see in this table at 1000 to 1200 rpm timing will be around 20deg or so > not good . You need around 30 to 32 deg in this area to maintain a good rolling idle AND the right cracker settings as well. Trial and error gets you good results if you understand the where and the why of what it is you are changing.
    A better way of acheiving this is to set B5917 to say 8 to 10km/hr thus limiting the use of base timing in gear table to under 10kh/hr with closed throttle, this way you can play around with the settings without affecting your main spark map in rolling situations. The other benefit is that overrun timing will use the main spark map until you reach 10km/hr. With your current
    settings it will use the base spark map pulling timing to 18degs on overrun which will give horrible engine breaking affect every time you close the throttle, together with no cracker at all which "slams the throttle shut" on overrun too.
    The next trick is to get the timing so when you go from base spark table (under 10km/hr) into main spark that the timing doesn't "jump" which can cause surge as well. Careful logging in this area and adjustment gives good results. Theres a lot to set up here but I have to say the timing maps leave a lot to be desired for a professional tune on a cammed engine....
    In the main spark map the classic hallmark of "lock the timing at 24degs at full load" sticks out like a sore thumb as does the "lock the timing after 2000rpm at any given load point". This IS NOT the way to tune an engine, shows a complete lack of understanding of tuning ignition timing and I would advise you to take it to a person that can do a full tractive effort tune so that the engine is getting the timing it requires....for your pockets sake!
    Other points I noted after a quick look thru...
    B5920 > disable smoothing also causes low speed timing issues when activated causing surge
    B6616 needs to be raised by 20% or so as a side note...you'll max out the 550nm no probs...
    I hope this helps sort a few things for you...its a lot to take in when you're trying to do it yourself...any further questions I'm happy to help.
    Cheers,
    Mike
    "Just a tune > yeah right !!!! "

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  6. #6
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by activity233 View Post
    ...

    Not sure what you mean by boost.

    Thanks for pointing that out, the original tune was done by a "professional" tuner, but there have been so many issues with it, no wonder they didn't want to unlock it. Would having the A4 segment in there be causing many issues, or should I change it to an M6?
    ...
    I saw the Boost VE table populated so I assumed you had an SC.

    Yes, change it to an M6 since this effects idle when you disengage the clutch.

  7. #7
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    Smile

    joecar and The Alchemist, thank you both for your replies.

    I have read what you have said and had a look at those threads.

    I have played around with the tune following your recommendations and am very happy to report that about 90% of the light throttle surging has now gone! it is still there vary slightly if you hold it between 1200 and 1800 at part throttle but no where near the back and forth bucking it once was. The car is now drivable again. Have also changed it to an M6 segment.

    I did the RAFIG process, but now sometimes when negotiating a tight car park it sometimes stalls, when say you have steering at near full lock. And sometimes rarely when coming to a stop, putting in the clutch the revs will drop to 300~400 rpm, sometimes it will stall and sometimes not. But when it does stall you have to crank it for a fair while before it fires. Is this to do withe desired airflow being to low?

    tune posted below.

    Thanks again
    Attached Files Attached Files

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    b4505 and 4506 change to 0.5sec gets rid of the delay for idle control to kick in ...

    base spark at 400 rpm up 3 to 4 deg and also at 0 rpm ie 30 and about 34. This acts as a spark backstop so to speak and ramps up spark as you go towards a stall. saves you most of the time ....
    And put 3g/s in throttle cracker table at 400rpm and 0 km/hr
    Last edited by The Alchemist; August 3rd, 2011 at 07:00 PM.
    "Just a tune > yeah right !!!! "

  9. #9
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    Just diggging up an old one, as I recently sorted out a surge issue of my own.

    I reckon I've seen this type of tune before.....

    You drop a lot of spark in the off-idle - 1200-1400rpm cells and I'm not sure why. I reckon if you add some timing across the 1200-1400cells, at the point where the surging is occurring - light throttle / load, perhaps the 0.12 - 0.20 g/cyl cells, you'll get a pleasant surprise. Don't be afraid to add up to 30 degrees across the affected cells and see whether it improves.


    The Alchemist - some pro tuners over here, whom charge $1000 a tune - use their base tunes which they've worked on to develop, then simply run the car up at WOT a few times to ensure it is running safe AFRs, let the O2 sensors look after the rest - and that is it! Most who do not know any better are happy with paying this, but those who are not, buy the software / WBO2 and do it themselves.

    cheers
    HSV Senator 300 - the Classy C4B...

    C4B - ETP215s 62cc, Comp 215/223 .601/.609 @111+3, Manley 8.050" 5/16" P/R, Morel Link-bar lifters, Powerbond 25% UDP, 36lb injectors, SLP pump, Rollmaster chain, OTRCAI, T-56 - RipShift, HydraTrak 3.91:1, DiFilippo 1.75" 4-1s, twin 3" st/st cat-back, 3" metal substrate hi-flow cats. AP-Racing 6/4-pots. EFIlive COS3 SD tune.

    308rwkW(413rwhp)

  10. #10
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    macca33 is correct. This was originally the work of a "pro tuner" in fact they seem to be fairly highly regarded as well as a sponsor to a major LS1 forum here. The original tune was hopeless, it was also locked without my permission. Their tune also threw out other things too like the fuel gauge. After spending thousands with them, I raised these concerns and they didn't want to know me anymore.

    I think with such a strong community with efi live that people should ask some serious questions of their tuner before dropping large amounts of cash or simply come here and do it themselves.

    Just an update, I have been fiddling with the tune since the original post and can happily say that now most if not all of the surge is gone.

    I took everyones suggestions, but I think the main changes that helped were a lot of work with the spark table, by adding a lot of spark where the surge was happening, but also I have had a WB02 fitted and the AFR was all over the place but seemed to be very lean in the areas where it surged, so adding fuel here seemed to help as well.

    Thanks

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