mike_d

i'm going to add a little info. i just did some more research because your post re-inspired me to continue working on my fake OBD project. from what i found, the pinouts are the same. i found a pinout (i still need to scan it in) for an '89 22-RE and it still has pin TIL (turbo indicator light) listed, so they were still using 22-RTE computers in '89 when (as far as i know) they weren't making any 22-RTE's.

they say that when testing the pins you need an input impedence of at least 10KOhms, if i were making circuitry for this, i'd go at least 100K or even 1M.

other useful information:

your WOT light will be easy, just need to test for 3-5V between VTA and E2 or 8-14V between IDL and E2. but the cool thing is that there's .1-1V between VTA and E2 for a closed throttle. so my guess is that between 1V and 3V on VTA you'll be able to watch how far open the throttle is. so if you wanted to get really ricey you could set up a line of LEDs that light up as the voltage between VTA and E2 increases from 1 to 3V. you may also want to look into IDL, it seems to have a bigger range, but i don't have any more info on that.

other cool things you could do: it looks like No.10-E01 and No.20-E02 voltage pulse for the injectors. as far as i can tell, there are two pulses sent to the injectors that each spray in 1/2 the amount of fuel needed. so you could measure the pulse length and knowing the flow rate for the injector and your speed, you could calculate your instantaneous gas milage. also it looks like you get aout 6-12V between STJ and E1 when the cold start injector is on. i think that'd be a cool LED to have. you also have 1-3V on THA-E2 when the intake air temperature is less than 68 degrees. and .1-1V on THW-E2 when the water temperatue is less thatn 176 degrees.

YotaTruck1986

WOW! Thanks for all the info Mike. That sounds pretty cool the "Fake OBD." I've been dreaming of some type of system like that where I could hook my ECU to my laptop. How do you connect your ECU to your laptop? Serial or USB? Thanks for the posts!

mike_d

well i haven't designed the electronics yet for the fake obd. i've just been gathering all the ecu info i can. but most likely it'll be serial for two reasons: my old laptop that i don't mind banging around in my garage doesn't have usb. and two: i have lots of experience writing serial interfaces to microcontrolers. i'm sure usb isn't hard, but i don't want to relearn that. unfortunately with grad school being so busy, this project has been going on for about a year now and i haven't even built any electronics yet. it'll be nice when i'm done with school and i can put some real time into my projects.

YotaTruck1986

That will be pretty cool, and you should definatly post your work. Are you creating a program on your laptop that will read the signals coming in from your ECU? Sounds pretty complex.

mike_d

what i'm planning on doing is creating very simple high impedence amplifiers to put on the ECU and then feed the output of those to an analog to digital converter. then it's very easy to just have the laptop read the digital signal from the ADC. then i can write a fairly simple program that just reads the ADC and then convert it to a real value. for example, if i plug into the AFM i can read a resistance that is mapped to the amount of air coming in the intake. the ADC will just spit out a number that i read on the laptop and then using emperical calibrations i can turn that into a mass of air. then it's easy to make a real time plot or log it to a data file or do anything i want with it. when (if) i ever get it done i'll be sure to post it.

YotaTruck1986

That'll be awesome. I can't wait to see your results.