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Thread: E38 PCM tuning experiences to share....

  1. #1
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    Default E38 PCM tuning experiences to share....

    hi there fellow forum fellows
    been doing lots of data logging on a Holden SS VE and getting a feel for timing requirements, fuel trims, and knock sensitivity and burst knock sensitivity and have found some interesting stuff that I would like to pass on.
    As we all know torque is in the timing, mostly, and the good ol factory tunes in the LS1 were average at best. With the Holden SS VE I found that it felt flat over 3000rpm at full throttle and the initial impression was one of disappointment.

    Logging showed 4 to 5 degrees knock retard occuring at 3000rpm on the button leaving the rest of the fun behind. Taking advantage of the multi cylinder knock sensor logging I discovered cylinder B ( hopefully not "B" for BOMB ) was the culprit. All the others logged "0". None the less knock retard retards total timing by 4 to 5 degrees.
    Timing was a retarded 12 degrees at full load at 3000rpm with the octane scalar right around at 1 due to all the "knocking" . The car made 194 kw , dyno dynamics, at the wheels on 91 octane gas. Timing at peak torque was 14 degrees (4500rpm) with no knock showing. Timing at 6000rpm was 16 degrees.
    Experience and logic says, to me anyway, that if it runs 14 degrees at peak torque with no knock, that it should be able to run at least 14 degrees at 3000rpm if not more. Time to investigate Cylinder B knock sensitivity. Gave it a tweak at the 2800 and 3125rpm points, a couple of test drives and hey presto no knock at 3000rpm. The sensitivity was much more trigger happy than the other cylinder knock maps. Could be a random calibration problem, could be that the cylinder B was more prone to knock during testing > not sure but I doubt it.

    Octane scalar learned closer to "0" and the car ran another 2 degrees under full load with NO knock registering anywhere on any cylinder.
    The car now pulls hard pass 3000rpm right up to 6000rpm and is much more impressive to drive. During all this I was also tweaking the low & high octane timing map downward by up to 10 degrees in places !!! to stop real knock with all 8 cylinders triggering knock retard. The car was on 91 afterall. The octane scaler self adjusts during these changes and I was keeping an eye on it.
    I also tweaked the low MAF calibrations by 2 to 4 % to bring long term trims down from 8% at worst to 0 to 2%. PE was also lowered accordingly as the AFR dropped out to 10.5:1 in the top end on the dyno.

    I'm now ready to throw it on the dyno again to see if my seat of the pants dyno reads as well as the dyno dynamics dyno. It certainly feels way better on the road so I'm sure I'll see a good result. We shall see.
    Then for some real tuning to find the timing limits on 91 octane with these engines. Will keep you posted.

    Just incase this reads wrong to people I don't tune cars by looking at knock sensor readings and adjusting timing for no knock. I use minimum effective timing for peak tractive effort. Its interesting to note that the factory PCM is actually set up to do exactly that > look at knock and adjust timing until there is no knock

    Its just that this was a new engine to me and new PCM and its easier making observations while on the road driving in real conditions and making some basic changes and observing response etc etc

    Mike
    "Just a tune > yeah right !!!! "

  2. #2
    Lifetime Member GMPX's Avatar
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    I'm just glad someone logged the knock per cyl data, it was a headache adding all that in

    Cheers,
    Ross
    I no longer monitor the forum, please either post your question or create a support ticket.

  3. #3
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    Quote Originally Posted by GMPX
    I'm just glad someone logged the knock per cyl data, it was a headache adding all that in

    Cheers,
    Ross
    Sorry for your headache but the ability to log knock per cyl is much appreciated !!

    ...
    I'm old and Retired! I used to go fast. I don't go so fast anymore ...but, my cars still do!

  4. #4
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    Quote Originally Posted by The Alchemist
    As we all know torque is in the timing, mostly, and the good ol factory tunes in the LS1 were average at best. With the Holden SS VE I found that it felt flat over 3000rpm at full throttle and the initial impression was one of disappointment.

    Logging showed 4 to 5 degrees knock retard occurring at 3000rpm on the button leaving the rest of the fun behind. Taking advantage of the multi cylinder knock sensor logging I discovered cylinder B ( hopefully not "B" for BOMB ) was the culprit. All the others logged "0". None the less knock retard retards total timing by 4 to 5 degrees.
    Timing was a retarded 12 degrees at full load at 3000rpm with the octane scalar right around at 1 due to all the "knocking" . The car made 194 kw , dyno dynamics, at the wheels on 91 octane gas. Timing at peak torque was 14 degrees (4500rpm) with no knock showing. Timing at 6000rpm was 16 degrees.
    Experience and logic says, to me anyway, that if it runs 14 degrees at peak torque with no knock, that it should be able to run at least 14 degrees at 3000rpm if not more. Time to investigate Cylinder B knock sensitivity. Gave it a tweak at the 2800 and 3125rpm points, a couple of test drives and hey presto no knock at 3000rpm. The sensitivity was much more trigger happy than the other cylinder knock maps. Could be a random calibration problem, could be that the cylinder B was more prone to knock during testing > not sure but I doubt it.

    Its just that this was a new engine to me and new PCM and its easier making observations while on the road driving in real conditions and making some basic changes and observing response etc etc

    Mike
    Like you Mike, I had a lot of KR with the factory tune that limited max timing to 18 degrees. I have done some street tuning with spark timing on my 6.2L and by increasing B1977 and B1978 both up to 150 along with some other changes have allowed me to get it up to 27 degrees on 91 oct with a little KR occasionally. It went from 362 ft lb delivered torque stock up to 401 with the timing changes. That made a major difference in the way it runs. I have not had any noticeable pinging. I didn't realize the potential advantage to log and change each cyl until now and I will go back to fine tune cyl KR sensitivity individually. Looks like a good improvement and we appreciate your efforts Ross.

    Ron
    2014 Silverado 4X4 6.2L
    2010 Camaro 2SS-RS L99
    2007 Sierra Denali 6.2L
    2005 1500HD 4X4 Quadrasteer 6.0L, COS3 SD

  5. #5
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    Quote Originally Posted by GMPX
    I'm just glad someone logged the knock per cyl data, it was a headache adding all that in

    Cheers,
    Ross
    Thanks Ross is was well worth it. Good idea having 8 knock sensors but only if they are calibrated correctly. Good work mate.

    Mike
    "Just a tune > yeah right !!!! "

  6. #6
    EFILive Reseller ringram's Avatar
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    Mike I hope you mean R+M/2 Octane or MON and not NZ 91 RON!
    Get EFILive in europe (http://www.efilive.eu).
    2007 Escalade ESV L92 6.2L VVT.
    2014 VF SV LS3 Maloo.

  7. #7
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    NZ 91 RON I'm afraid to say..... it was already in the car. I asked the owner and he said he was told it would run on either 91 or 96 when he brought it !!! The timing tables are set up for more like our 98 RON and are hopelessly advanced for 91 RON.
    At least when I get this right the damn thing will be to scared to KNOCK
    Dynoing it today and will post results for you and the other members
    Mike
    "Just a tune > yeah right !!!! "

  8. #8
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    Been logging a HSV VE of late it's running 98 fuel and has not showed knock to be a problem the tune was very good from stock 12.5 afr & 22/23 deg at wot . air temps are a problem stoped at the lights i see 60/70 and down to around 30/40 driving with out side temp around 15 deg . taking off at the lights i was seeing -7 deg of air temp spark retard . a cold air system looks to be a must

  9. #9
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    hey there ntae, you couldn't post up that tune file could you. It would be interesting to see that calibration changes between the base model and the HSV model.

    Cheers,

    Mike
    "Just a tune > yeah right !!!! "

  10. #10
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    The file looks to be to big for the forum i will host it somewere hold on

    email your stock file to admin@ntautoelectrics.com.au i will host it as well the NZ file could be the same as the OZ

    Geoff

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