How the 4A-GE ECU works

[dAYTONA]

I just got a quick question..

Will the 4AGE ECU make use of a Oxygen/Lambda Sensor if it doesn't have one from factory. I think there is a pin for the sensor on the ecu, but does anyone know if it actually is active?

Thanks.

[Denmark]

Do you sell this program,so that the user can map the ecu themself?

regards,
Skassa

[JMR_AW11]

dAYTONA Wrote:I just got a quick question..

Will the 4AGE ECU make use of a Oxygen/Lambda Sensor if it doesn't have one from factory. I think there is a pin for the sensor on the ecu, but does anyone know if it actually is active?

Thanks.

On the UK MR2 4A-GE ECUs the car has a manual mixture adjuster instead of an oxygen sensor.

On at least one of the UK ECUs the mixture screw uses the Oxygen sensor input pin!

I wrote another article on the mixture screw a few months back for the MR2 club magazine. I'll try and upload it to my website asap.

I doubt your ECU will support a proper Oxygen sensor.

[JMR_AW11]

Just added a quick 3D graph to my web page to show ignition timing in degrees BTDC.

I think I have got the conversion correct.

I tested it with an oscilloscope on the IGT wire and it seems to check out OK.

Skassa,
The ECU has to be modified as well. The software will not work on a standard 4A-GE ECU.

[alimonos]

JMR how can we start these hidden-secret(for race use?) programms in our ECU?

[JMR_AW11]

alimonos Wrote:JMR how can we start these hidden-secret(for race use?) programms in our ECU?

With a pair of wire cutters.

Seriously, on the UK ECUs these maps are locked out with a wire link which sets a logic level in the ECU.

These extra maps may only be present in the UK ECUs.
They are there on the UK MR2 and AE86 4A-GE ECUs.

I'll post the AE86 stock and secret maps on here when I get the chance and maybe someone can advise on what they are for.

It may just be for lower grade fuel (or for a different country?)

On some ECUs you may have to add a wire link rather than cut one.

[firehawk]

Quote:I would imagine one EPROM contains all the program code and one will contain the mapping (the socketed one).

That's what I thought as well. I'll have to try to follow the address lines from the CPU to the EPROMs and PIA to see how they're mapped into the address space. The "001" EPROM appears to be 32Kbit, while the other one is only 16Kbit. It would seem possible that the code is mapped to $F000-$FFFF because the reset vector on 6800 series CPUs is at $FFFE:$FFFF. The lack of an external RAM chip on the board would suggest that the mystery ND chip might actually be a Hitachi 6301 or 6303.

This is actually getting so exciting that I probably have to remove both EPROMs from the board, then dump them and disassemble the code to satisfy my curiosity - It's been a while since I've done some proper reverse-engineering.

Quote:I am very surprised they use a cheap pressed ribbon cable connector to interconnect the two PCBs. I would have thought a direct soldered 0.1" pitch ribbon would have been more reliable and worth the extra expense. (i.e. that's what I use)

Indeed. The 3S-GTE ECU consists of two boards which are connected with a quite solid ribbon cable soldered directly onto the boards just as you described. The cable used by TRD, however, is more flexible so they may have chosen to use if they've thought that the two boards need to be often removed from the casing and put back. I can't, however, see why one would need to do this as the EPROMs are easily accessible after just removing the upper lid of the casing. Maybe they had originally thought that the piggyback board would be mounted in the casing component side down.

[JonT]

Hi Jeremy, pleased to see you continued with this, there are lots of people who would be after an affordable programmable unit, me for a start.

[Denmark]

This is great,

can you make a price on what it would cost if the ECU is shipped to you,and then you modified it!,
Put in the OE maps again,but on the the new chip,so it can be modified!.

The cable needed to connnect to the laptop,and the program!.

This is what we all need,but a Q?.

can the map sensor get changed and the maplimit,so the car can be boostet, and still use the oe ECU, or would it then be better to use MS, or some other ECU

Regards,
Skassa

[phatBob]

JMR_AW11 Wrote:Just added a quick 3D graph to my web page to show ignition timing in degrees BTDC.

Have you got a URL for that please? I had a look at your site and couldnt find anything specific. I can patch it into the VEMS ecu tomorrow. I will be moving the 20V onto coil on plugs in the next few days so to run on a 'proper' ingition advance table would be really good. Even with bad accel enrichment setup the engine feels really lively and responsive, although it can take a lot of advance it seems to be good with only 25degrees total advance. I'm a Honda man with Nissan leanings but these Toyota engines are ver impressive.