How the 4A-GE ECU works

[np303]

"the stock ECU has a hidden diagnostic capability"

does anyone know anything more about this?

[SuperHessu]

Hmm... I have an ECU for my AE86 which is made for Group-N rallycars, and I could'nt pass the emissions test's with it so I started to examine. I used an 80's Toyota tester called the TCCS-checker which basicly is connected between the ECU and wiring harness and allows you to display all the sensors signals. Well all the sensors were ok, but I notest a very okward thing, I could disconnect the TPS-signal from the ECU and it had no affect on the engine at all I opened the ECU and there were a few things changed:

1. I don't know what theyre colled in english but they're the things that have resistance, I thould they're changed to alter the signals to "fool" the ECU to run the engine "wrong" as in richer.

2. There were a few black boxes changed, the kinda that have lots of "feet" around them connected to the board. [ LOL at my english vocabulary ]

3. There was a wire on the board connecting two dots that werent originally connected.

Questions:

1. If the stock ECU doesn't use the TPS signal nearly at all as you said, could it be that the Group-N ECU has been modified to ignore it totally??

2. Could that extra wire be there to get an other map running??

To np303: As I have the engine in TE-71 I had to make some of the wiring myself and the stock AE86 ECU has a diagnostic ability similar to newer Toyota ECU's. Meaning it displays trouble codes by flashing a LED.

If you want I can take pics of the ECU board this weekend, I bought a stock ECU for my AE86 so it's free for examination. Oh and by the way, have you ever gotten familiar with the Saab ignition system?? I'm working as a Saab/Mercedes/Honda/BMW/Citroen mechanic so I have. I'm planning to use a Saab-ignition cassette on my 4A-GE, which basicly allows you to sensor the firing quality inside the engine It'll be sometime next year that I'll have time for this thou..

[NoHachi]

Do you know of any people that have succefully installed the Saab Ion sensing iginition into other cars? I know that a lot of people tried but failed..very interesting technology that would allow a HUGE improvement in tuning capability.

[SuperHessu]

NoHachi Wrote:Do you know of any people that have succefully installed the Saab Ion sensing iginition into other cars? I know that a lot of people tried but failed..very interesting technology that would allow a HUGE improvement in tuning capability.

Haven't heard of anyone even trying yet, but I have all the original wiring diagrams etc. and I've discussed them with experienced car-electric mechanics and we've all agreed on how to run it succesfully with a MegaSquirt for example.. The wiring is rather simple actually, it needs a solid 12volts, 12volts while ignition on and a ground. Then you control the ignition by connecting the correct pins to earth making the plugs ignite, and then there's two pins giving out the knowledge of the burning, they're grouped so that cylinders 1 and 2 come though one pin and 3 and 4 through one. That's so that the original Saab system would know in what position the engine is. At first when you start the car it uses the crankshaft position signal to get clear of which cylinders are up, and then ignites on 1 and 4 or 2 an 3, then it just checks which pin gives out the fire signal. Naturally if there's a spark on 1 and 4 and the pin of cylinders 1 and 2 tells of a burn, it knows where to ignite next and keeps igniting only one cylinder at a time.. Saab systems don't have a knock sensor at all, but the system keeps monitoring if the cylinders ignite before there's even a spark and that way knows if the engine is knocking.. I'm not gonna try to use that feature but only to get a look at the firing seguence and burning quality to be able to adjust the engine even better..

SORRY FOR THE OT!

[banpei]

np303 Wrote:"the stock ECU has a hidden diagnostic capability"

does anyone know anything more about this?

http://www.aeu86.org/viewtopic.php?t=749

[Ivan141]

That's hardly a hidden feature now is it, I suspect JMR ment something else.

[irishtwincam]

SuperHessu Wrote:2. There were a few black boxes changed, the kinda that have lots of "feet" around them connected to the board. [ LOL at my english vocabulary ]

Microchips.
Your vocabulary needs work but you are very "articulate".
you can describe what your trying to say very well

SuperHessu Wrote:3. There was a wire on the board connecting two dots that werent originally connected.

JMR mentions that there is a jumper/wire that needs cutting/joining to enable the race map. Please post pictures of where this is done.

Also the resistors are a known trick. They are probably on the water temp sensor to make the car run rich. Possibly some variable resistors to alternate the map signal to force timing changes.
Igt->Igf is probably joined also.

[banpei]

Ivan141 Wrote:That's hardly a hidden feature now is it, I suspect JMR ment something else.

Ah right. I totally misread the post.

[alimonos]

irishtwincam]

[quote=SuperHessu Wrote:3. There was a wire on the board connecting two dots that werent originally connected.

JMR mentions that there is a jumper/wire that needs cutting/joining to enable the race map. Please post pictures of where this is done.

[/quote]

RACE MAP ????
Hmmmmmmmmm.......
PICS PICS PICS

[Bad_Dog]

JMR_AW11,

great work!

Do you have the IGt sygnal scoped? I badly need it both during cranking and running. Thanks