BAC5.2 Posted February 28, 2011 Share Posted February 28, 2011 To those that have the MPG needle in the dash. What happened when you swapped in big injectors? Does the needle just jump around all the time, or does it behave normally? Obviously the MPG numbers are going to be totally wrong, but it should be a linear multiplier, right? [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
Th3Franz Posted February 28, 2011 Share Posted February 28, 2011 Yeah one would expect a linear multiplier. I've been pondering how I could hack it to read correctly again. It's precise, but inaccurate. I get 32 mpg now! -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
rao Posted February 28, 2011 Share Posted February 28, 2011 It will behave normally, but it will be off by the ratio of the new injectors to the old ones. It will be linear. My car always seems to think I am getting in the mid-20's around twon and over 30 on the highway, but that isn't even close Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
BAC5.2 Posted February 28, 2011 Author Share Posted February 28, 2011 Great. Thanks for convincing me to do fuel mods guys. I briefly thought about hacking the CAN, but that's impractical. Its easy to read CAN signals, but changing them is somewhat more complex. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
rao Posted February 28, 2011 Share Posted February 28, 2011 I want to be very clear here - I think the fuel mods are a bad idea. That money could be spent for better projects CAN is easy read, very hard to write. Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
BAC5.2 Posted February 28, 2011 Author Share Posted February 28, 2011 True. But I can't start any new projects for at least another year and a half. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
BAC5.2 Posted March 1, 2011 Author Share Posted March 1, 2011 So, in my OCD nature (and my deep, deep hatred of having non-functionality in the car. It's been almost 2 years, and I still hate that SAT button on the radio), I'm going to explore the possibility of hacking the CAN bus. So far, I'm aware of how to connect to CAN, make data requests, and so fourth. Requests are easy. Hardware is coded on-board to request and display information. Changing those requests on hardware is more than I want to get into (but does have benefits, like the possibility of turning the MPG needle into a boost gauge, for example). The difficulty is changing the source of the requested information. For this application, changing the algorithm that produces the requested output. MPG calculation here. I BELIEVE that average MPG is calculated through some transform of the instant economy data, and that is done at the hardware level (the combi-meter performs the average itself). Even if it's done at a CAN level, it references the "instantaneous" MPG calculation. I can probably sniff out where the request is stored on the ECU, but changing the input for that location might prove immeasurably difficult. Since the display is off by a fixed percentage, it's obvious that injector flow is some fixed value not linked to the value set when tuning the car. Everything else modifies accordingly (duty cycle and pulse width). If I'm lucky, finding the source of the MPG calculation will expose references within the ECU for calculation variables. If I'm right, and the injector size is fixed within that code, it should be a matter of just changing that number to my new number (1100 I guess, if I use ID1100's) and calling it good. If I'm unlucky, the algorithm monitors silly things like fuel pressure and IDC/IPW and makes assumptions about fuel flow based on that (scaled output with respect to fuel pressure and duty cycle). Changing that should just be adding a multiplication factor of the percent increase of new injectors versus old injectors. If I'm REALLY unlucky, I'll be able to find all of this information, but I'll have absolutely no way of changing it. I think I need a tactrix cable, and to build a CAN operator. I guess it's a good thing that I still have a PC laptop kicking around in my office that I can use. I doubt anyone has CAN interface software designed for a Mac. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
Squiden Posted March 2, 2011 Share Posted March 2, 2011 ^ In for results - I'd love to have a way to change the output to read correctly! Link to comment Share on other sites More sharing options...
BAC5.2 Posted March 2, 2011 Author Share Posted March 2, 2011 So far it doesn't look possible. I'll keep looking though. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
brou4164 Posted June 10, 2011 Share Posted June 10, 2011 bump for any update? My car read 45mpg, I actually got about 20..... Link to comment Share on other sites More sharing options...
BAC5.2 Posted June 10, 2011 Author Share Posted June 10, 2011 As with most projects, I've had other things take priority over this. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
brou4164 Posted June 10, 2011 Share Posted June 10, 2011 I understand, does that mean you're giving up on this venture? Link to comment Share on other sites More sharing options...
BAC5.2 Posted June 10, 2011 Author Share Posted June 10, 2011 For now, yes. To many things on my plate right now, and I have to minimize. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
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