GeneralDisorder Posted July 9, 2006 Share Posted July 9, 2006 I haven't played much with the SPFI, and so I'm curious what experiences people have had with disconnecting the Evap purge, and EGR systems. I'll leave the solenoids in place for the computer.... I have done this plenty of times on carbed engines with no effect, but there's also no software interface there. Does anyone know or has anyone experienced strange behaviour from the computer if the pre-determined amount of exhuast gas is not present? Does it run too lean from the extra oxygen present in the intake charge? Or will the rest of the system (MAF, 02, etc) compensate by telling the computer it needs more fuel? Am I making this way to complex? I'm a software engineer, and I would break into the silly thing's ROM if I thought I would be able to do anything with it. Sadly I don't want to risk wrecking the only computer I have at the moment... (but it's tempting to think about trying - just to save out the fuel maps for later mega-squirt use). I also want to turn the IAC valve upside down so the solenoid is on the right side - this will help to clear the disty on the EA81 - any problem with that other than it's hose routing? I took it off, and it doesn't seem to be oreintation dependant as far as I can tell.... GD Quote Link to comment Share on other sites More sharing options...
SOOBOUTLAW Posted July 9, 2006 Share Posted July 9, 2006 I dunno about Subaru SPFI, but on alot of other cars with computers, you can just disconnect the battery for a few mins to an hour, then reconnect and let the motor idle for a certain time to let the computer reset itself. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 9, 2006 Author Share Posted July 9, 2006 I'm not asking how to reset the computer, I'm asking if the computer is hard coded to expect exhaust gas or not. And I need to know if turning the IAC upside down will affect it - doesn't seem to be oreintation dependant, but then I'm not totally familair with it's theory of operation either - I don't have an EA82 FSM. GD Quote Link to comment Share on other sites More sharing options...
azsubaru Posted July 9, 2006 Share Posted July 9, 2006 I think you'll find some disagreement on this, but I don't think you will notice anything at all if you just plug off the EGR valve. I haven't noticed any difference after about a year with mine blocked. Had the purge disconnected for a while, also didn't notice any difference in power or gas mileage. Can't really help with the IAC valve, but I don't know why it would matter as long as it it fits. Quote Link to comment Share on other sites More sharing options...
keltik Posted July 9, 2006 Share Posted July 9, 2006 Regarding the IAV, looking at mine - its a pretty simple piece of kit and i cant see why it wouldnt work the other way around. As for the EGR and Evap systems, I think the best answer for you would be to go out and try it, unplug the stuff and go for a hoon around the block. As the ECU has to adjust for changing O2 levels anyways, i dont think you'll hve a problem. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 9, 2006 Author Share Posted July 9, 2006 I did decide the disconnect the EGR and the Evap stuff. I left the solenoids in place to fool the ECU. I turned the IAC over, and bent the two vacuum supply lines to the side to clear the intake hose for it. I'll block them off as they supply the EGR and Evap that I already removed. GD Quote Link to comment Share on other sites More sharing options...
NorthWet Posted July 9, 2006 Share Posted July 9, 2006 I would imagine that the EGR (and purge, for that matter) changes would be well within the closed-loop envelope of the map. A smart engineer/programmer would anticipate for failures in the EGR and purge, and allow the system to compensate rather than risking engine damage. Quote Link to comment Share on other sites More sharing options...
85Sub4WD Posted July 9, 2006 Share Posted July 9, 2006 I agree with NorthWet on the EGR and Evap stuff - I think it should compensate, though I havent personally tried blocking it the IAC valve should be fine to rotate 180* - the solenoid is a pretty sturdy unit good luck on cracking the software - if I did have a spare ECU - Id send it to you - Im a EE student, and I cant find much info out about how to access the memory chip in it - there are two basic types of ECUs for the SPFI system - one had the memory burned-in on the CPU, its a gray box - the black ones have a seperate EPROM or something like that which is reprogrammable (both boxes are interchangeable - theres no difference in wiring harness or anything like that) - the MCUs are Hitachi and appear to be similar to the Motorola 6800 CPU - they run good-ol C of course - I found some info about them in pdf format if you want it - I'll have to dig for it though - PM me if you want it and I can email you, Id love to see SOMEONE crack it Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 9, 2006 Author Share Posted July 9, 2006 I'll give it a whirl - I can always get some ECU's at the junk yards around here - there were 30 EA82's at least at my local yard yesterday. Many or them SPFI. I have a friend who's an EE guy from way back - got his degree 15 years ago. I'll probably enlist his help with the hardware portions of it. He's a software engineer now, and we are both assembly nuts - if it's straight C it should be relatively easy to dissasemble, or I could just go through the assembly code line-by-line too. I'm sure it's a simple chip - probably something like the 6800 as you say - that would be a perfect chip for a small closed system like this. What would be neat is to rebuild the interface of the ECU for a serial or parrallel connection and run the whole software interface from a laptop. GD Quote Link to comment Share on other sites More sharing options...
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