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Thread: Why no DSP for LML?

  1. #61
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    Jan 2010
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    Thanks for the help, I'll report back when/if I get it working. Didn't realize you were Ben, The standalone harness you built me for my race truck still works great.

    Quote Originally Posted by DURAtotheMAX View Post
    Also, on the fuel temp sensor SOTF...

    There are several other changes required that are outside of what EFILive has mapped in their tuning tool.....

    1. You have to enable "fuel temp sensor 2" on the 2012+ OS's. Because only 2011 trucks had two separate fuel temp sensors from the factory. 2012+ it was unused.

    2. You have to change the scaling of the measured-voltage-to-temperature table for the fuel temp sensor #2. Basically what B0212-B0213 does in an 01-05 LB7/LLY tune file. Note I said 01-05 LLY. You wont find B0212-0213 in an LML tune because EFILive does not have it mapped.

    3. You have to disable range-extension of the fuel temp sensor. The ECM has a forward-biased pullup resistor inside it with a little FET in there that can change the value of the pullup resistor on the ADC input of the fuel temp sensor circuits. Obviously all ADC inputs to ECU's have to have either a somewhat high-impedance pull up resistor to +5volt reference, or a pulldown resistor to low-reference. Otherwise the ADC input would float erratically and not give accurate readings. Its also buffered with an op-amp in voltage-follower configuration...but I digress.

    Anyway, the IAT and ECT sensor inputs have this feature too. Its to give the sensor more accuracy throughout its range of -40* to 300* or whatever. Think of it like high range vs low range in a transfer case. Around 130* or so, the ECM triggers the FET to change the pullup resistor value so now instead of the thermistor referencing a 10k ohm bias to +5v, its using say 5.6k pullup value.

    If you dont disable the range switching, when you change tunes to the point of the ECM reading around 130*, it'll switch that internal FET and the readings from your DSP switch will then get all screwed up and it'll jump from like 130* to 200* or something. Then your B0457 table becomes all wrong again.

    Or I guess you could also just carefully tweak sensor scaling range 1 table and sensor scaling range 2 table independently so even when it switches ranges, the measured temp value is overlaid/corresponds properly despite the shift in pullup bias....but thats probably more of a pain.


    The rest of the stuff you need is right in EFILive. B0457, and the axis modifier tables....because B0457 only goes from like 220-260* or whatever, you need to broaden the range to give a greater difference in the fuel limiting factor value.

    2015-2016, there are a couple extra things you have to do....you cant directly copy-pasta all changes from 2011-2014 OS to 2015-2016.

    Its not rocket surgery, I messed around with this "DSP" method like a year and a half ago and it worked alright...but I didnt know as much about working in the LML binaries back then because I didnt own an LML until october 2015, so Id never worked on them before....so I wasnt able to figure out how to disable the sensor range-extension feature....so I had to make a complex DSP switch with some extra logic in there to compensate and change its outputs at the same time the ECM changed the pullup value. If I had all of the LML documentation and A2L, it would have been easy-peasy. The concept is simple as hell.

    But I abandoned the EGR temp/fuel temp sensor based "DSP" because I never liked the idea of sensor-fooling just because its not true mode switching, I think its kinda ghetto/hack...but thats just my own stupid opinion. So I pursued my CAN-based method that actually commands the ECM to change modes and put all my eggs in one basket with that. Yeah, it was probably dumb of me to do that, should have kept the EGR/fuel temp based "DSP" and just said "screw it, good enough, uses existing DSP switches, inexpensive, works alright"....but whatever, thats because Im a true out-of-the-box tinkerer/engineering-design nerd and NOT a business man.

    Ben

  2. #62
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    Mar 2017
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    any way to do the fuel temp or egr temp method with out going into cax and all that. id like to do it on my 2012 but after playing around with winols for awhile I give up on that lol.

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