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Thread: E35B Digital MAF Scaling

  1. #11
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    kidturbo, If you send me your current CAX I'll just add in the stuff Ross has for you then you can see how to stack multiple parameters onto one CAX file.

    It isn't rocket science, just a bit of a learning curve figuring out the syntax for CAX files.

    Shoot me a PM if you would like some help with it.

  2. #12
    Lifetime Member GMPX's Avatar
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    I've just had a look at this and the axis is defined in 'uS', we converted those values to Hz because for most people that would make more sense. I think that is why we went for the fixed values because we couldn't do the uS > Hz conversion on the axis values. But there is a BIG problem, the axis is defined using 16 bit signed values (no idea why they used signed), so the maximum positive value is 0x7FFF, the end value at the top of the axis from factory is 0x7F9E, meaning there is nothing left, you can't go over 0x8000 or the numbers become negative. I think you are stuck with what is there unfortunately.
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  3. #13
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    uS for a maf scale?

    What if we do something like the Subaru guys and half the scale, then half the table axis' that reference the scale?

  4. #14
    Lifetime Member GMPX's Avatar
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    Quote Originally Posted by SASDakota View Post
    uS for a maf scale?
    Don't shoot the messenger.....it's Bosch

    Quote Originally Posted by SASDakota View Post
    What if we do something like the Subaru guys and half the scale, then half the table axis' that reference the scale?
    I guess if you can figure out where in the OS code they set that up it might be possible, but I don't know what flow on effect that might have elsewhere in the system.
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  5. #15
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    That's interesting. Leave it to Bosch to over complicate things..

    What about on the Analog option? Looks like half the cells in that table axis are set to 5.00 for a reason. Could we improve on the resolution by adjusting that axis to fit better with a 910gps hard limit?

    While not my ideal solution, adding two 5v signals together is actually easier than adding dual Hz inputs. That's basically all I'm trying to accomplish, tally up two MAF signal values into a usable total the ECM can work with. Do they even still make Analog MAF's...

  6. #16
    Lifetime Member GMPX's Avatar
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    Can I throw my hands in the air on this one?
    I don't know what the ECM's internal limits are with air flow though or even if the same limits apply to both frequency and analogue MAF inputs.

    Also I'm not sure what you mean by adding two 5V signals together, to be fed in to the same input?
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  7. #17
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    Quote Originally Posted by GMPX View Post
    Also I'm not sure what you mean by adding two 5V signals together, to be fed in to the same input?
    It's on a twin turbo setup. Was considering combining two separate MAF Hz sensor signals into a single output using a micro controller. However those output totals could exceed the ECM's 15khz max limit shown in my first post from bench testing. So I would need to place limits on the Hz output from the controller, no matter what the actual total. As where with voltage MAF setup, limit would be standard 5v max. Easy.

    Anyways, if we can't increase axis values to up around 14-15khz, then there isn't much to be gained by this exercise. Resolution can't be improved, so will just remap within existing scale. Not ideal, but what are the other options?

  8. #18
    Joe (Moderator) joecar's Avatar
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    What are you trying to do again (your original objective)...?

  9. #19
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    Not sure if it's completely applicable here, but I know gas guys simply increase the tube size the LS3/7 card-style MAF sits in to change the resolution. Going from a 3" -> 4" tube means the overall speed of the air decreases (lowering MAF values) while keeping the same mass of air flowing into the engine. Downside is you lose resolution at idle and part-throttle.
    ~Erik~
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  10. #20
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    Quote Originally Posted by joecar View Post
    What are you trying to do again (your original objective)...?
    Change the digital MAF axis from 8696hz to around 14khz so we can run the new style GM digital MAF's with 12khz frequency range. In first post pics you can see the ECM understands a 15khz input signal from an emulator.

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