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Aaron's Custom ST16x Econometer

Discussion in 'Electronics' started by aaron, Feb 6, 2012.

  1. aaron

    aaron Well-Known Member

    As some of you may know, I have been working on an econometer for our cars that can either replace the tacho or be mounted somewhere else.

    I just thought I'd make a thread of my progress for those interested.
    So far it's a few circuits and a screen on a breadboard, I've been focusing mainly on the software.

    Here is a few pics of the guages and menus:
    [​IMG]
    P1030175 by DeL337--, on Flickr
    [​IMG]
    P1030179 by DeL337--, on Flickr
    [​IMG]
    P1030180 by DeL337--, on Flickr
    [​IMG]
    P1030181 by DeL337--, on Flickr
    [​IMG]
    P1030184 by DeL337--, on Flickr
    [​IMG]
    P1030185 by DeL337--, on Flickr






    I have a 555 timer hooked up simulating injector pulses right now, I'm not too worried about the pulse width ( hence why the L/min seems very high ), it's just for testing.

    I'm open to any suggestions for new features and modifications.

    I'm programming it in metric, but it can easily be converted for Imperial/US measurements if any of you guys across the lake are interested.

    Aaron.
     
    Last edited: Feb 6, 2012
  2. Zaluss

    Zaluss Well-Known Member Donated!

    I so want this.

    How would this be installed in our cars? What sensors would be needed etc.

    Oh and a price! :p
     
  3. Spiderman

    Spiderman Well-Known Member

    Very clever, I'm interested.

    Aaron said "The end product will probably come out at around ~$20-$30 cost price."
     
  4. aaron

    aaron Well-Known Member

    No need for extra sensors unless you want them, like oil pressure etc.. It taps right into the ECU lines.
    You can install it anywhere you like, but the screen I'm using fits almost perfectly in the Tach hole, plus it has a tach on it.

    That's only a guess at the moment, the microcontroller itself only costs about ~$5, PCB ~$6 and the screen is ~$7.
    The rest of the components are a matter of cents each.

    I don't mind selling at cost price, but if anyone feels like they're stealing from me I'm happy to haggle :p

    Aaron.
     
  5. Thaifighter

    Thaifighter Well-Known Member

    Nice!!!

    $20-$30 isn't bad at all!
    I paid $70 (before shipping, and after $9 rebate) for an Ultraguage, which plugs into the OBDII port (I got this for my new car, not the Celica, haha) and has like over 60 gauges that I can monitor, from MPG to Boost Pressure, to diagnosing CEL's...

    Maybe you could do something like that... :) It would be nice to have something that could display MPG and stuff like that without the need for an OBD port... (Cause I haven't seen anything like that in the market yet.)
     
  6. aaron

    aaron Well-Known Member

    I will never understand why devices like that cost so much, all it is is simple data analysation.

    I could incorporate a CEL diagnostic program in the econometer if it would help people.
    I could pretty much read and display anything that uses a sensor; boost pressure, oil pressure, even G forces if I wanted to.
    All I have to do to display pretty much anything is a small amount of math.

    Would people like a CEL diagnostic program?

    Aaron.
     
  7. celica_gt-i

    celica_gt-i Well-Known Member

    Great work Aaron :D
     
  8. CelicaSteve

    CelicaSteve Well-Known Member Staff Member Super Moderator Donated!

    It's just business, that's the way it is :rolleyes:

    I love what you're doing !
     
  9. Stig

    Stig ST162 Guru Donated!

    Put me down for one

    How about exhaust temp, AFR, oil temp - those gauges seem to cost the earth!

    How do you meter the fuel?
     
  10. aaron

    aaron Well-Known Member

    If there's a sensor for it, I can read and display it.

    AFR is just simple math too, read how much fuel is being injected, read how much air is being sucked in via the MAF, and parse the data.

    The fuel is fairly simple, the injectors have a CC/min value and they are told how much fuel to squirt using Pulse Width Modulation. I set a hardware interrupt to run a routine whenever an injector fires, measuring how long the injector is open for with microsecond accuracy and multiplying that time by how much fuel is squirted in one microsecond, giving me how much fuel was injected.

    Aaron.
     
  11. 4thgenceli

    4thgenceli Test Dummy

    Whats the chance this will work with a swap?

    My fuel gauge no longer works... think I borked or fubared the sender. I'd like something like this that'd display all that data.
     
  12. lone wolf

    lone wolf Well-Known Member Donated!


    I strangly had the same...switched 2 cablles at the gastank and now it works again. :)
     
  13. aaron

    aaron Well-Known Member

    What do you mean by work with a swap? If it's the engine you swapped then it doesn't matter, it will still display accurate data.

    It doesn't use the data from the fuel sender at all, you just tell it how much fuel you put in when you fill the tank up and it calculates exactly how much you've used by by sensing the injector squirts.

    Aaron.
     
  14. 1fstgts

    1fstgts Well-Known Member Staff Member Administrator Moderator Donated!

    Pretty cool stuff. If I wasnt going to a Standalone Id be hitting you up for one. Glad to see another electronics guru on the site.
     
  15. 4thgenceli

    4thgenceli Test Dummy

    I understand that, my question is will it work with swaps?

    You say it uses the stock sensors for data (oil pressure, coolant temp, RPM, etc). Does it matter what engine? Will it be universal or motor specific (ie I can't use one setup for a ST162 3s-ge with a ST215 3s-gte).
     
  16. Stig

    Stig ST162 Guru Donated!

    So how do we "adjust" for injector swaps - I run 315 injectors, JDM is 165 and the rest are 295

    Also I discovered that flow rate doesn't equal the listed flow, most injectors flow 5-10cc less than listed
     
  17. aaron

    aaron Well-Known Member

    It will be universal, you can change the reading values of all the sensors.
    RPM is always universal because it read the injector fire rate, coolant temp and oil pressure will probably vary for every sensor. I can get the base value for the 3S-GE/GTE coolant sensor and oil pressure gauges but anyone with a swapped engine might need to test the sensors at known values ( one high, one low, one in between ) and read the resistance for each.
    I will try to find any information on commonly swapped engines that I can, but someone with each engine might need to read the sensors and I'll add the values into the software.

    The CC/min value is adjustable, but there really is no way to compensate for clogged/lower than rated value injectors without expensive flow rate sensors ( believe me, they cost a lot more than the actual econometer ). If you can get your injectors' true flow rate you can set it and get perfect data.

    Basically everything is adjustable, but I will try to find the right values for everyone's engines if I can.

    Since I'm designing both the hardware and software, I can pretty much anything I want with it as long as I keep within 16 thousand calculations per second :p

    Aaron.
     
  18. aaron

    aaron Well-Known Member

    Just noticed this. It might not matter what ECU you have, as long as your speedo still sends VSS (speed sensor) pulses to it and it sends injector squirt signals.

    Aaron.
     
  19. Spiderman

    Spiderman Well-Known Member

    Yes please :thumbsup:

    BTW, does anyone know if any 4th Gens came with a vacuum gauge instead of a tacho ?


    BAH ! is that all, lame :mrgreen
     
  20. 4thgenceli

    4thgenceli Test Dummy


    Yes, the alltrac.
     

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