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Thread: Question about Greg's DVD data.

  1. #1
    Advanced Tuner angrygoat's Avatar
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    Question about Greg's DVD data.

    How is it all the minimum pulsewidths are the same for all the injectors on his spreadsheet except one? The short pulse limit is the same way. TIA
    Last edited by angrygoat; 10-21-2009 at 07:38 AM.
    Joe
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  2. #2
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    The SPL is 4.0 on ANY injector used on a GM. As Greg previously told me:

    IT doesn't really matter if it's 2.6 or 4.0, since that just defines the base PW under which the adder will be used. If you have a base PW of 3.1ms for example, this would be under the 4.0 threshold but the adder table is adding 0.0 to it, so it's a moot point. It works out the same either way, and the "official" GM method calls for the threshold to be 4.0 all the time with whatever adder necessary in the SPA table, even if it's zeros.
    As for the Minimum Pulsewidth, that's what is called for in Greg's conversion process, as well. The 80# injector requires 1.1, however.
    Last edited by RWTD; 10-21-2009 at 02:39 PM.
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  3. #3
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    i would love to see the math behind all these different injectors spitting ONE value for all these different injectors....

  4. #4
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    Quote Originally Posted by redhardsupra View Post
    i would love to see the math behind all these different injectors spitting ONE value for all these different injectors....
    And your point is?

    I assume you are commenting in regards to the MP, since the SPL scalar is really moot?
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  5. #5
    Senior Tuner eficalibrator's Avatar
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    Quote Originally Posted by redhardsupra View Post
    i would love to see the math behind all these different injectors spitting ONE value for all these different injectors....
    1) For the short pulse threshold, the reason is shown above: You can always set it to 4.0ms, and it *might* just add a zero to the raw pulsewidth if you're out of the nonlinear range. The Short pulse adjust table is doing the real work, not the threshold scalar/element.

    2) Theoretically, you could readjust the min PW for each injector but what you're really looking for is the ability to consistently deliver whatever the injector's minimum fuel mass is. It has been my experience that most injectors are good down to about 0.8 to 1.0 milliseconds, so I tend to allow them the option to go there IF the calibrator requests such by way of airmass and AFR selection. The 80's are the one notable exception where I've seen data that proved they were only stable to about 1.1ms and their min PW is set accordingly in my data.

    If you've got more conclusive data, I'm all ears and encourage everyone to use it.

  6. #6
    Advanced Tuner angrygoat's Avatar
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    Another question. I know the IFR is different depending on whether you are using a return style or returnless fuel system, correct? Are there any other changes that need to be made? I thought I once read that the 0kpa column of the offset table gets copied all the way across the KPA row
    Joe
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    "The goal of tuning is for the tune to run well enough you dont need any corrective mechanisms"

  7. #7
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    Quote Originally Posted by angrygoat View Post
    Another question. I know the IFR is different depending on whether you are using a return style or returnless fuel system, correct? Are there any other changes that need to be made? I thought I once read that the 0kpa column of the offset table gets copied all the way across the KPA row
    Yes, if you are running a return-style system, you should ALWAYS have a vacuum/boost referenced regulator, therefore you'd set your IFR table to be the same ACROSS the board as the 58 psi value for that parameter (that would be 0 kPa on some calibrations, and 400 kPa on others). Also, the same goes with the Offset table - you'd copy the 0 kPa column (the whole column), or 400 kPa, depending on calibration across the entire table.
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  8. #8

    Question for tuning gurus

    Stock Bosch LS7 injectors are rated at 42 lb/hr @ 58 PSI.
    The factory calibration shows 41.737 lb/hr @ 58 PSI in the flow rate vs pressure table.
    I have a set of flow matched Stock Bosch LS7 injectors that flowed 42.6 to 42.7 lb/hr @ 58 PSI.
    I have measured the fuel pressure at the fuel rail on 4 different C6 Z06's and they were between 64-65 psi.
    Also the minimum injector pulse width is .797 msec for all cells in the stock calibration, less than 1 msec.
    How would you modify the injector control tables to reflect the measured values of the injectors and fuel pressure?
    Last edited by wstaab; 10-23-2009 at 03:04 PM.

  9. #9
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    You should trust the factory calibration.
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