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Thread: e38 unexplained timing spikes while working on vve

  1. #1
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    e38 unexplained timing spikes while working on vve

    For some reason every time I touch the stock vve table to tune my new cam, I get wild advance and retard spikes randomly while cruising. The vve table is smooth. The delivered engine torque spikes also. Maf is failed. All 4 vve tables are the same. I can't be the first person to have this issue. I've searched every way I can think of. What am I missing. thanks 12:34 and 12:41 time
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    Last edited by fastNYsix; 04-18-2022 at 12:54 PM.

  2. #2
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    im interested in what you find. im having similar issue with e38 and vve tuning. i somehow cant rule out whether i have the wrong MAP sensor or though. good luck with it

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    Quote Originally Posted by fastNYsix View Post
    For some reason every time I touch the stock vve table to tune my new cam, I get wild advance and retard spikes randomly while cruising. The vve table is smooth. The delivered engine torque spikes also. Maf is failed. All 4 vve tables are the same. I can't be the first person to have this issue. I've searched every way I can think of. What am I missing. thanks 12:34 and 12:41 time
    All I saw in the log was normal TM between shifts, fast torque exit, decel stuff. Looks normal to me.
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    its definitely not torque management. There is no shift occurring, the accelerator pedal is not moved, the converter is not applying. Every time it happens, there is a spike either up or down with engine torque delivered, and then timing tries to correct by advancing or retarding. The truck shakes violently, KR spikes. Luckily the 45 degrees of advance hasn't happened at wot.

    Screenshot 2022-04-18 212810.png

  5. #5
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    here's a clip of a spike where engine torque is 1300 ft lbs at 1200 rpm and timing drops to zero.
    Screenshot 2022-04-18 215123.png
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    Last edited by fastNYsix; 04-18-2022 at 08:59 PM.

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    Actually surprised Alvin didn't catch this since he pointed out in another thread. It's some sort of checksum error going on in the ecm. Torque goes through the roof. Timing plunges (you can assist the timing plunge with the mbt table sometimes). AND if you look at your afr error - it also spikes showing where it dumped fuel for a split second. Only fix currently is going to a 2bar OS. Unfortunately you don't have that option, so I recommend tuning in your MAF and then using a math parameter to tune in your VVE. Your welcome to use this one.

    (([50041.223]*(273.15+[50011.241]) * (1000/[50030.91]))
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  7. #7
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    Quote Originally Posted by GHuggins View Post
    Actually surprised Alvin didn't catch this since he pointed out in another thread. It's some sort of checksum error going on in the ecm. Torque goes through the roof. Timing plunges (you can assist the timing plunge with the mbt table sometimes). AND if you look at your afr error - it also spikes showing where it dumped fuel for a split second. Only fix currently is going to a 2bar OS. Unfortunately you don't have that option, so I recommend tuning in your MAF and then using a math parameter to tune in your VVE. Your welcome to use this one.

    (([50041.223]*(273.15+[50011.241]) * (1000/[50030.91]))

    I simply didn't see it and am used to people freaking out at timing dipping during decel and stuff that I figured that's what it was.

    You might be able to make the situation better by rezoning the MAP and RPM boundaries. But yes some have this VVE bug that will not seem to completely go away. You should be able to get it down to only happening once every 30 minutes of driving or so.
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    GHuggins. Ok thank you. I couldn?t find any info on this issue. So which tables will I be changing when using your formula? The truck came with 5.3 not the 6.0, I didn?t think it would be this hard to do the swap. hp tuners shouldn?t allow the vve to be changed then if the process doesn?t work and could cause engine damage from extreme timing advance. If I go back to stock cam, can I copy and paste the entire vve tables from 6.0? Or will I still have the same situation? Thanks
    Last edited by fastNYsix; 04-19-2022 at 02:50 PM.

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    Alvin.. Ok thanks. When the maf is reenabled does it stop happening? Once is more than enough for my liking. But you?re right it doesn?t happen often.
    Last edited by fastNYsix; 04-19-2022 at 02:50 PM.

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    IIRC, I had a similar issue with timing dips and spikes creating a buck you could feel while cruising. It was solved by correcting my torque model. I had modified the torque map at some point and did not smooth- that was causing the issues I had.
    Hawk

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    When I use your formula and leave the maf enabled, the bucking hasn't returned. The formula gets me very close to commanded vs actual afr. I'm not sure what I am missing but, my commanded afr is 14.00 and when I log gmve, the new value is reflecting that I'm rich, when I'm actually lean.
    Last edited by fastNYsix; 04-25-2022 at 03:07 PM.

  12. #12
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    It's far better to turn the MAF off, Dial in the VVE, then turn on the MAF again to finish. The formulas will help you rough it in but ultimately the MAF is too noisy to deliver a great result.
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    ive been playing with the IDLE ADAPTIVE SPARK CONTROL on mine. I cut the numbers in half and it seemed to smooth it out a bit. I can still tell its there but not nearly as bad. not sure if you want to look into that any but i do think that cutting those numbers in half enriched my AFR some so, just be aware of that. if it dont like it, you can always change it back. Just thought id let you know what i have found by experimentation.

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    thanks ls rob, I haven't messed with timing that much yet. Another thing that makes the timing spikes less aggressive I noticed, is having the vve absolutely smooth. Also When I would smooth the vve and calculate coefficients, I didn't check the values after. Now I do. Sometimes it was still not smooth after calculating and I'd have to smooth again and recalculate. Even with the vve glass smooth, I can't drive the truck with the maf disabled or it will buck from the timing dips and spikes. I looked at your log and your spikes looked different than mine. When I get the timing spikes, I also get a spike in engine torque delivered and cylinder air spikes. I also added every timing modifier channel to the scanner to try and catch the problem. My issue seems to be air related, When my cylinder air drop I get the max timing commanded from the main spark table. Mine is actually commanding the ridiculous timing without any timing modifier. I'm a little lean now at 14.5 but at least I can drive the truck without worry of blowing a head gasket or breaking a piston. I've submitted a ticket to hp, they've been responsive but needed better logs.
    Last edited by fastNYsix; 04-27-2022 at 10:36 AM.

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    im interested in what you find. ill keep an eye on your thread

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    I submitted the logs that hp tuners requested, but got no response. The truck runs pretty decent now. I've went back to almost stock timing table for now. I smoothed the high octane table and reduced timing in some areas I was getting knock. I'm not running 93. Idles at 750. The timing spikes are gone with maf enabled.

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    thanks for updating

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    I had a similar issue in SD mode. The fix was to zero out the AC clutch toque management. For whatever reason, it was pulling a ton of timing when the AC compressor was commanded on. Zeroing out those tables stopped that. May or may not be your issue, but if you have not zeroed out these tables, might be worth a shot.

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    ill look into that. thanks for sharing danmw2003

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    Quote Originally Posted by danmw2003 View Post
    I had a similar issue in SD mode. The fix was to zero out the AC clutch toque management. For whatever reason, it was pulling a ton of timing when the AC compressor was commanded on. Zeroing out those tables stopped that. May or may not be your issue, but if you have not zeroed out these tables, might be worth a shot.
    It doesn't look like this is what the OP has going on, but ac torque reduction happens in blended mode as well. Someone on this forum pointed me in the right direction. In my case it was a hard single fishbite feel during a light cruise speed, as strong as a sudden dead misfire. Zero'd out this chart to resolve. Now, if we could only disable the ac clutch in the cal from banging on and off at WOT....