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  1. #11
    EFILive Distributor dfe1's Avatar
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    Yes, we do know about MAFs, but my point is that after switching to a Custom OS and making no other changes, the car ran just like it did with the original OS (according to data logs). When I switched to SD, with no other changes, the LTFTs jumped a bunch. There is obviously a difference in the way the system processes the VE table in SD versus Mass Air mode. Nothing that can't be corrected with a little tuning, but tuning does have to be done.

  2. #12
    Guess who's back!!!! Black02SS's Avatar
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    Quote Originally Posted by dfe1
    Yes, we do know about MAFs, but my point is that after switching to a Custom OS and making no other changes, the car ran just like it did with the original OS (according to data logs). When I switched to SD, with no other changes, the LTFTs jumped a bunch. There is obviously a difference in the way the system processes the VE table in SD versus Mass Air mode. Nothing that can't be corrected with a little tuning, but tuning does have to be done.
    This is what I am saying, some of us don't have a MAF on the car anymore. I personally noticed that when I went from my "tuned stock" tune and changed it over to OSV3, my startups were a lot worse. I have had to fiddle with them to get straight. I don't think, if nothing in the OS has been touched, we shouldn't have to do this. Nothing should change on the car side if the tune is the same as the one you put in before, except you have a few more tables now.

  3. #13
    EFILive Distributor dfe1's Avatar
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    Quote Originally Posted by Black02SS
    Nothing should change on the car side if the tune is the same as the one you put in before, except you have a few more tables now.
    I don't agree. I don't mean to imply that this is the gospel, but in my experience, the LSx engine control system is not a "pure" Mass Air system. It's more of an interpretive system that uses both predicted and measured air flow to determine fuel and spark control. When actual air flow data is eliminated from the equation, the system obviously has to rely fully on predicted air flow (VE table-driven). If I switch back and forth between my Custom OS2 MAF and MAFless tunes, the car runs the same and LTFTs are really close, but the VE tables are completely different. My guess is that under normal circumstances, the MAF input is compared to predicted data and if it's within range, more reliance is placed on MAF than predicted data. I don't know this for certain, but I'd guess the arrangement is similar to the sliding scale used between the high and low octane fuel tables. Consider too that the spark tables are referenced to air flow readings. If there's no Mass Air Flow sensor in the system, how is spark controlled? Obviously, the system has to rely on computed air flow, based on load, (MAP) rpm and TPS voltage

    By comparison, a pure Mass Air system, such as the ones used on the 1986-89 Tuned Port cars, relies exclusively on MAF sensor data, and doesn't even have a VE table or a MAP sensor. The LT1 Mass Air systems do have a VE table and MAP sensor, but this appears to be strictly for back-up purposes in the event of a MAF sensor failure. Changes to the VE table seem to have no effect if the MAF is functioning properly.

  4. #14
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    Maybe it's me, but if the VE table is set up in SD mode plugging the MAF in should have essentially no effect on trims or anything else. If it does it would seem like the MAF table, B5001, is off and the trims are correcting for that. Now if something in the intake tract has changed so the flow the MAF sees is messed with, increased reversion or something that pushes the air to one side of the MAF there's no telling what might happen.

    Ira

  5. #15
    Guess who's back!!!! Black02SS's Avatar
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    I think this thread got way off track. Here is what I am saying regarding the first post. If the car was dialed in Mafless with a stock tune, you transfered all your existing tables over to the custom os and it now it doesn't start the same way, where is the problem? Theoretically IMO it should start in the same manner as before.

  6. #16
    EFILive Reseller ringram's Avatar
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    FWIW I had this exact problem. It was well weird. It turned out that the .cal files for the custom os were not overwritten by the install and didnt match the .tun.
    Maybe you should check that the cal files are in the right places.
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  7. #17

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    This may be a stupid question but when you go a set a new custom OS tune for the first time;Other then loading in the custom .tun file that matches the current OS, does the .cal file also need to be dragged into the picture??

    All I did to start the custom OS process was open up the appropriate custom 2/3Bar SD OS and flash it into the PCM, and then load back in a stock matching .bin file. Once you double check some of the "sane" values it theoretically should at least start....


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  8. #18
    EFILive Reseller ringram's Avatar
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    Mine looked right, but it wasnt. You can check the cal version. Should be 7.74 now.
    The OS needs to match the cal. I think the .tun is the binary file and the cal is the "filter" which interprets it correctly. If they dont match weird stuff can happen.
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  9. #19
    EFILive Developer Site Admin Blacky's Avatar
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    Anyone having fuel issues, please check the value of {B3601} "Air Fuel Ratio for Stoich". It should be 14.63
    Some old *.cal files had an incorrect max limit of 1.0 which forced it to down to 1.0
    If that has happened the PCM will attempt to command 1:1 AFR (way too rich) when it should be shooting for 14.63.
    If that valus has changed, please change it back.

    Unrelated, the {B0106} "Crank:Run Blend Ratio" may also get incorrectly altered to 1. It's stock value is 8.

    Both of these two limits have been corrected in the latest *.cal files. But the *.tun file you are using may have been altered previously using a faulty version of the *.cal files.

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    Paul
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  10. #20
    Lifetime Member MN C5's Avatar
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    Thanks...guys.

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