legacycentral bbs

Thanks for the contribution.

I built an EPROM reader/EEPROM writer about a year ago, but instead of using a DIP socket I used a card-edge connector so it would be easy to read and write Select Monitor cartridges. I think I'm just gonna build another one with a socket on it for chips.

And, yeah, like I said, the 8-bit ECUs have industry-standard EPROMs on them.

I looked through Renesas' site, and found the same thing. The problem is that the processor in the 16-bit ECUs is a 7700 series, not a 7900. It's a 7791, I believe. Renesas has info on the more recent 7700 series processors, but I actually found a changelog page that said in 2000 they removed the 7790 information.

The general 7700-series information has plenty of info on the opcodes and such but I have no information on the architecture of the 7790 in particular (like the hardware registers, memory mapping, etc). I have found that it is different from the others, but a little similar. For example, I was able to manipulate the UART using the same addresses as more modern 7700-series chip.

Gad. I'd get much farther in my explorations if I got the part number right, eh? Hmmf.

Nevertheless, I found some tech poop on the 7700 series, and I'm all hot to trot to diassemble this code.

Question to all: Are there any sites/bbs/covens who are tinkering with this breed of ECU (older legacies)?

This one. :)

If you'd like the complete dump of this ROM PM me your email address. Technically it's copyrighted or whatever so I shouldn't post it publicly.

Guys, this might be a little astray from vrg3's purposes here and it is definitely a worn-out issue. But he might stumble upon this in his studies and I unfortunately still have this issue...

I have done everything people have claimed have fixed their hesitation issues. I have an updated knock sensor, I have a new alternator, I actually cried "cure" with the motor mounts, when I really didn't test it enough, so that wasn't it. I have NGK V-powers gapped at .040", and my engine is otherwise in a perfect state of tune. But I still have this aggravating hesitation!!

So, delving into the shallow depths of my ECU knowledge , I believe that the ECU is pulling timing because it detects knock. Is it the engine's fault? No, it's flawless. Is it the knock sensor's fault? No, the sensor is new and has been updated. So whose fault do I think it is? I think it's the ECU's! I think that the ECU is actually overreacting to input from the knock sensor and pulling timing in accordance. I also wonder if this contributes to the EJ22's rock-solid reputation of being so dependable: the ECU babies it unneccesarily!

vrg3, I am curious if you can find some particular evidence of this as you dissect one of our ECU's. Maybe you can hook one up to a running motor and watch the engine pull timing under conditions where it's probably not needed...

Again, I don't know a whole bunch about ECU's, except what they do. So what I have just said is speculation. But I have thought about it this way for a while, and was wondering if vrg3 could research this as he plays around with it.

Thanks for bringing this up -- it is something I have definitely planned to examine. Saying the engine is flawless may be a bit strong, but you're right that the engine computer ought to be able to compensate for any flat spots or anything in the engine's powerband.

Right now I'm actually working on a very low-cost engine monitor that should allow a lot of us to better understand what our ECUs are doing.

Or maybe those dips and hills aren't from a bad rom transfer it's actually what the maps look like.

Hmm, maybe you're right! I'll have to dump the memory again and take a look. If that's so, I wonder if it's by design or by defect, though... It doesn't seem like a problem that would be hard to fix.

Okay, I've dumped the ROM from my EJ22T ECU, and its data area appears to be a lot harder to understand than the 92 non-turbo's. I can't make good sense of the maps and find their axes intuitively.

My current plan is to try to watch the ECU's behavior and infer what the maps should look like, so then I can find them more easily. It's given me a lot more respect for dyno-tuning. It's really hard to test all the load sites on the road. It's especially hard to reliably get high-RPM high-load conditions. Even loading hard with my brakes (WRX brakes in front with Axxis Ultimates, Legacy Turbo in rear with Axxis Metal Masters) my engine wouldn't stay loaded at those speeds.

Okay, I've got some interesting stuff, I think:

http://www.graphics.cornell.edu/~v/pics/aa694.gif

There seem to be two ignition timing maps. One has quite a bit more advance at loads above idle. It would appear that the one with more advance indicates the maximum permissible advance and the one with less indicates the base timing. The ECU presumably then learns (through knock sensor feedback) the best value inclusively between the two maps. These maps do seem to jibe with my datalog of my ECU's timing versus load and RPM.

The MAF sensor calibration looks different on this ECU than it did on the 1992 non-turbo ECU. The sensors themselves are different, so maybe this makes sense.

I haven't found anything that looks like a fuel map. It's really weird. I did find this unusual 16x16 map that I can't identify (note in the above figure that the axes are inverted to show the shape of the surface; the values are highest at the origin).

I'm just going to add to your confusion but if you took this data from an auto ecu could the second map be from "Power" mode? If it was from a manual just ignore this, also what other maps could there be? Something from the o2 sensor? Or some other sensor?

The EJ22T ECUs are all the same, automatics and manuals. So this ECU is for both kinds of transmissions.

Power mode is operated entirely by the TCU; the ECU doesn't know anything about it.

I have read about WRX ECU tuning and apparently the way it works is that it has an ignition map and an "ignition advance map" that tells it how much it's allowed to advance. I'm pretty confident that this is the same sort of thing here, except it has two ignition maps instead of one map and a delta map.

There are like a gazillion 8x8 maps in here. I'll get them all out and show you guys... I'm not sure about their axes but maybe their shapes will be meaningful. The thing is, I doubt the fueling map is 8x8. It's bizarre that I can't seem to find a 16x16 fueling map.

I come with a possible gift.

I'm getting an underdriven alternator pulley. go fast bits are the only ones who make one. However I didn't want to buy a set....anyway I'm buying the pulley through autospeed. Was doin some looking around and found this book.

http://www.autospeed.com/cgi-bin/browse ... roduct=852&

The thing that caught my eye is they show a pic of a timing map......I would assume they have similar info for fuel and other stuff. There seems to be a lot of stuff covered in it too. I would think if you can find this book at amazon or some other place, it would be worth your while to get, and see if it has any info you could use in hacking at your ecu & maps.

http://us1.webpublications.com.au/stati ... ry_3mg.jpg

Interesting; thanks, Josh! Amazon does apparently carry it. Anyone have 35 extra bucks they wanna give me? :)

I think I have a good idea what ignition and fueling maps should look like... I'm just amazed that I can't seem to find anything that looks at all like a fueling map in the ROM of my EJ22T ECU. Maybe I should dump another Hitachi ECU's ROM for comparison. The small bit of disassembly I've done hasn't revealed much, but I haven't had time to reverse engineer it hard core.

What if the extra maps are fail safe maps? When the ECU detects some errors it will set fixed values for the item? Maybe the maps you found are for when the oxygen sensor or MAF is removed?

ciper, you're probably right about some of them. I just want to figure out exactly what they're maps of.

As crazy as it sounds, I'm unable to find a fuel map in the turbo ECU's ROM. The code is hard to follow but I'm working on it on and off. I wish I could find a datasheet for the Hitachi HD63140CP chip; it would make sense of a lot of the I/O.

If I could just figure out how to remap fueling I'd be happy for the moment. Remapping ignition and fuel are of primary importance. If beyond that I could remap boost and adjust injector size (at the proper part of the computation instead of just changing the fuel map or MAF calibration) I'd be set.

vrg3, check out http://www.pgmfi.org

Thanks for the link. A lot of that site seems to talk about engine tuning, which is a stage I haven't even reached yet. My current hurdle is understanding the code. It's interesting, though.

Those guys all hacked the code of Honda ECUs and wrote their own software to modify it for forced induction. I thought it might give you some inpiration.

Yeah, it certainly does, and it is helpful to read about a system parallel the one I'm working on.

I heard you did some engine control mod, but i cant find any info on it. Can you give me some details?

http://bbs.legacycentral.org/viewtopic.php?t=14620

http://bbs.legacycentral.org/viewtopic.php?t=1505

http://bbs.legacycentral.org/viewtopic.php?t=16219

pm him if you have more questions, or maybe start a thread somewere else. I think this thread is soo content filled it should probably stay on track. No offense.

VRG... still tinkering with the ECU? I work with embedded microcontrollers every day, 24MHz mixed-signal chips programmable in C and Intel-based assembly. Maybe I could help you look at some of that ECU dump and make sense of it - I too would like to be able to alter my fuel and timing maps.

On a completely unrelated note, I have a Megasquirt that I was building for my late Turbo Saturn, which was wrecked by someone that wasn't paying attention to a stop sign. Which brings me to my Subaru, which has much more potential than the Saturn anyway... but at any rate I do have a half-assembled Megasquirt that I havent touched in a while. I'm into this kind of stuff. Gimme info

I'm not working on it at the moment because I'm pressed to finish up with school, but I will be returning to the project shortly.

If you'd like a copy of the ROM dump of my ECU, drop me an email (my address is at the bottom of my web page).

Sorry to hear about your Saturn. What model was it?

MegaSquirt is cool... that's what my brother and I are using on his MkII Supra now that we've turbocharged it. Have you read about UltraMegaSquirt?

keep us posted!

V: Have not kept up with the Megasquirt groups, didnt even know they had an ultramegasquirt - I'll have to check that out. I had a 1999 SC2 3-door with a rebuilt garrett T3 super 60 turbo, it was finally running 4psi intercooled with the stock 9.5:1 CR and not doing too bad - all I needed was the megasquirt, injectors, fuel pump, and different year head to lower the CR and I was prime to run some decent boost in that thing. It was just FWD though, I'm much happier with my Scooby. Still hurts to see all that work go down the drain though, I did all that in my friggin driveway with my friend and mostly junkyard parts. Even welded my own downpipe together. But oh well.

What are you studying? I just finally graduated this past semester from UCF with a degree in computer engineering. Very glad it's over with.