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Thread: Bolt-on LS7 with big spikes in timing, any help welcome

  1. #1
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    Bolt-on LS7 with big spikes in timing, any help welcome

    Okay, so I've already searched for answers on here and have read a few people having similar issues, but no real answers. Most of the people who experienced problems like this had aftermarket camshafts and just needed to pull timing at lower Cylinder airmass/rpm. For me, I would think my stock Z06 tune should run with zero drive-ability issues. I tried this regardless, with no luck.

    Vehicle details:

    2007 Z06 with 15k miles
    -Halltech MF103 intake
    -Ported stock TB (by Tony Mamo)
    -Intake shroud cut for more air-flow
    -160* T-stat
    -B&B fusion cat-back
    -TR55 plugs .040" gap

    I bought the car with 12.4K miles on a stock tune with zero issues running these mods
    -Halltech MF103
    -B&B fusion cat-back
    -Then I added the TR55 plugs, still no problems.


    Again, the main issue is large drops in timing while cruising at low rpm and low cylinder airmass. The spikes usually happen between 21-30% TPS (NOT accelerating) and of course cause severe bucking . I believe I can't get the LTFT's perfect because the timing is constantly dropping and raising back to normal, too. Now, anytime I accelerate, the car runs very smooth. The harder I accelerate, the more spot on the tune seems to be.

    *Another note* I went to "The Tuning School" last November, so I got one year of free tech support. When I called them, sent a tune/datalog, they said they've only seen this a few times and each time there was either a ground problem with the ECM or the ECM was defective in some way.

    IMO, I don't think this is the case, for one main reason. As a test, I turned off virtual VE, fuel enrichment, COT, DOD, AND disabled MAF High. After doing this, I was able to completely eliminate all the surging and bucking. That being said, the LTFT's would never dial in very well and as soon as I turned MAF High back on, all the surging came back and got worse. I realize that was not a fix, nor the way you should do things, but it did get rid off all the surging, which is interesting. So, if you can get rid of the surging that way, how could there be a mechanical problem with the ECM ground or overall ECM??

    I should also note that I originally planned to tune this car MAF only and disable VE (I'm not familiar with Bluecat, but plan to be in the future). I originally had it disabled, then enabled it back on to see if this would help the issue, but saw no change.

    Any help would be much appreciated! I'm going to post my datalogs and tunes in a second. I just didn't want to write this on my tiny netbook...
    Last edited by camONLYls1; 10-18-2012 at 06:35 PM.

  2. #2
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    This is the current tune and a recent datalog

  3. #3
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    This is the test tune with MAF High turned off. I was able to completley get rid of all surging/bucking with this tune. Again, the LTFT's never looked good though..

  4. #4

    Scan file

    Can you post a scan with the issue along with config file.
    2011 GMC Sierra 4X4 SLE Lysholm 2300 Supercharger 5" BDS Lift, 33X12.50X20 Nitto's and 20" Chrome Wheels.

  5. #5
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    Quote Originally Posted by hhoelle View Post
    Can you post a scan with the issue along with config file.
    My second post has a scan file attached showing the problem in dropping spark. Here's the config file, too. Thanks in advance!


    *side note* the NGK AFX wideband isn't hooked up in the scan becauses it wasn't reading properly on my HPTuners for some reason. I have to play with it another time.
    Last edited by camONLYls1; 10-18-2012 at 08:16 PM.

  6. #6
    Your Second tune is actually running in MAF with STFT and LTFT enabled. The MAF is not failed. You have to set the DTC P0103 to MIL on first error in order for it to fail the MAF. Not sure if your MAF has the IAT in the same connector but if it isn't disconnecting the MAF needs to be done also. When running n SD your extremely lean in the area of your issue. I suspect while you're in MAF it runs richer and therefore you won't have the lean spikes. This is probably causing your problem. How are you tuning your SD it is very lean in spots and very rich in others? If you do a search There are several good posts on tuning the SD with BlueCat if you want to tune it in SD.

    I suggest you tune it in MAF until you research the SD tuning procedure for VE tuning. Hope this helps.
    2011 GMC Sierra 4X4 SLE Lysholm 2300 Supercharger 5" BDS Lift, 33X12.50X20 Nitto's and 20" Chrome Wheels.

  7. #7
    The timing dips you can see are most likely from spark smoothing, turn of spark smoothing and do another log, I'll bet all the timing dips disappear.
    2010 GXP Maloo ute, LS3, 6L80E.
    MM heads, 240/252@50 solid cam, 12.75:1 compression, 4500 Dominator converter, 3.46 rears.
    Shooting for 10s eventually.

  8. #8
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    Quote Originally Posted by hhoelle View Post
    Your Second tune is actually running in MAF with STFT and LTFT enabled. The MAF is not failed. You have to set the DTC P0103 to MIL on first error in order for it to fail the MAF. Not sure if your MAF has the IAT in the same connector but if it isn't disconnecting the MAF needs to be done also. When running n SD your extremely lean in the area of your issue. I suspect while you're in MAF it runs richer and therefore you won't have the lean spikes. This is probably causing your problem. How are you tuning your SD it is very lean in spots and very rich in others? If you do a search There are several good posts on tuning the SD with BlueCat if you want to tune it in SD.

    I suggest you tune it in MAF until you research the SD tuning procedure for VE tuning. Hope this helps.
    The second tune, I just disabled the MAF High Frequency. MAF Low Frequency was still working/running and for whatever reason, this made me be able to get rid of the timing spikes with some tuning.

    Now the first tune where Virtual VE is still enabled, although it was originally disabled, but I re-enabled it to see if this would help with the timing spikes. It did not help with Virtual VE enabled or disabled. I'm going to disable Virtual VE again though, because I don't quite understand the Bluecat program yet. I need to do some more reading first. So, until then, I will be running MAF only.

    Again, I've already tried to tune this car with Virtual VE disabled and it did not help the timing spikes. One thing I haven't tried is disabling Spark Smoothing.. I'll give this a try, but from what I've read, I shouldn't have to do this with a very stock car..

    Thanks for your advice, it's much appreciated!

  9. #9
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    Quote Originally Posted by Xjas View Post
    The timing dips you can see are most likely from spark smoothing, turn of spark smoothing and do another log, I'll bet all the timing dips disappear.
    Thanks for this tip! I'll give it a try tomorrow morning and see how things go. I'll disable the Virtual VE as well, so the car will be running MAF only when I disable Spark Smoothing.

    I'll let you know how it goes!

    Shane

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    Okay so I didn't get too much time to mess with the z06 this weekend. However, I did turn off spark smoothing and go for a quick ride. It seemed to get rid of the sharp timing spikes, but I still get bucking in the same low cylinder airmass/ rpm cruising speeds. Plus, my A/F at those points won't dial in either.

    I could try taking out a little timing and doing a lot of hand smoothing in those positions tomorrow. Although, it really confuses me why I would have to lessen those stock timing tables for just a bolt-on vette...

    Have you guys ever cut the intake shroud on a c6 corvette and had a hard time tuning it? I feel this is what's throwing the tune off so bad. I had zero problems before this mod (that I did a 160* t-stat with). After a few weeks, I got the TB ported because I planned on tuning it and of course it ran worse with the ported TB.

    I'll let you know how this turns out, but I have little faith it will be perfect.

  11. #11
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    the test tune massairflow failed high dfco is turned off ie 258 degrees ...in the tune with bucking you complain about it is turned on ie 86 degrees hth

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    Quote Originally Posted by turbo 6l View Post
    the test tune massairflow failed high dfco is turned off ie 258 degrees ...in the tune with bucking you complain about it is turned on ie 86 degrees hth
    Wow I can't believe I missed that. I'll set the dfco to 258 on my "normal tune" and see if that helps. I imagine it will, however, why wasn't I able to dial in the Air/Fuel on the "test tune" with the MAF high failed or the "normal tune"? I can see how it could affect the one with dfco still turned on, but why the other?

    Either way, as soon as the streets becoming drivable (z06 worthy lol) from Hurricane Sandy, I'll disable dfco and see how it does. Thanks for pointing that out, sometimes I get so caught up in the more complicated stuff, I miss small easy things!

    Shane

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    something else i missed last time maf low at 5800 hertz vs maf high 5800 does not match i hear they have match ..torque management/ engine/max torque 1gear 2gear 3 gear etc raise the limit say from 300 ftlb torque to 550 or max it out ...not to sure maybe some traction control maybe working unless you are flipping the switch to off inside the car hth

  14. #14
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    without looking at the map
    without reading any answer

    change your plugs to TR6

    Zo6 LS7 doenst like Tr55 plugs
    they are to hot for the car

    Tr6 ,, u will gain more power , no Knocking

    good luck

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  15. #15
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    I bought the tuning school books and tried using their method of calibrating VE and MAF with LTFT's. Car just didn't run right. I pitched the books and went back to using my wide band and AFR error. Got the error under 2% and many of the little odd behaviors just went away...
    When arguing with an idiot, make sure he isn't doing the same thing....

  16. #16
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    Hey guys!

    Sorry I haven't written back in way too long. Apologies for that!

    The car is "fixed" to an extent. I ended up calling Halltech and talking to Jim Hall. He said you can't cut the intake shroud with his intakes because the MAF sensor is too far forward and there is too much turbulence to get a solid MAF reading.

    This is what I figured was happening, but I thought there was a way to tune around it. Either way, I bought a new plastic shroud for $38 bucks and all the timing spikes went away. In fact, the stock tune worked pretty well, but of course I cleaned it up a bit.

    NEW PROBLEM- I'm only commanding 19-20* of timing WOT at 5k-7.2k rpm, yet I'll see the timing climb up to 25-26* starting at 6.2k rpm. I've been looking at other tables that could possibly add timing like that, but nothing looks out of whack. Initially I was commanding 22-23* and seeing as high as 27.5*. So from the main spark table I pulled timing down to 19-20* ,but I know that's not the right way to solve this problem.

    Any suggestions for tables to look at? I'm at work now, but I can post the tune up later tonight. Thanks again for the tips in advance!

    Shane

  17. #17
    Zero out the timing in the AFR corrections tables and all the cat lightoff stuff. Turn off spark smoothing and log spark again and see if it climbs.

  18. #18
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    Quote Originally Posted by meatbag View Post
    Zero out the timing in the AFR corrections tables and all the cat lightoff stuff. Turn off spark smoothing and log spark again and see if it climbs.

    Thanks for the advice. Everything is straightened out and the car is running great. I'm not sure which table was adding the timing, but everything is squared away at 23* of max timing at WOT now.

    Thanks to everything else who put in their suggestions, as well!

    Shane