How the 4A-GE ECU works

[Ivan141]

Very nice work...some more info on you custom microcontroller setup would be interesting. BTW Zax, there is a dutch guy that has been remapping 4AGE ECU's for age's, but he hasnt disclosed any info since he made money remapping ECU's for ither guys. With some proper tuning software this might be an interesting thing to toy around with..
Imagine the benefits for relatively normally modded engines (cams, intake, exhaust), if you could get a proper map for it and run it using the factory ECU, with all the fancy correction factors still in place (possibly modded lightly as well)...
The trouble I suspect lies in making good mappings.

[irishtwincam]

http://www.mr2mk1club.com/

More of the same info here, been looking for the earlier articles actually!

[JMR_AW11]

NoHachi Wrote:Do you happen to know to what inputs the accel-enrichment is related? Only delta TPS or is there an rpm/map/watertemp reference as well?

The accel enrichment code is different for every UK 4A-GE ECU type I have looked at.
However, it always runs off a rapid change in the MAP sensor not the TPS.

The TPS has very limited functionality inside the ROM code for the UK mk1 MR2 ECUs.

I've not really studied the throttle enrichment code too closely though. Mainly because it is so different on each ECU type.

HTH

[JMR_AW11]

dreja Wrote:Respect

As I can see, the adapter replaces 4age microcontroller. Which microcontroller do you use at the adapter plate?

If the user decides to reprogram some data, what does he has to do: reprogram the microcontroller, reprogram the eprom or only set the microcontroller's parameters through pc with using a communication (serial, can, etc.)?

Regards
Andrej

I use a MCU with external FLASH memory that supports the same instruction set as the original MCU. I also use a custom chip to recreate some of the special I/O functionality of the original MCU. This custom chip is a fully programmable logic device which allows me to create I/O ports, registers and memory cells etc.

With my latest version, all reprogramming is done via a laptop. No need to unplug any chips. All done via the serial port into secure FLASH memory.

[JMR_AW11]

Ivan141 Wrote:Very nice work...some more info on you custom microcontroller setup would be interesting. BTW Zax, there is a dutch guy that has been remapping 4AGE ECU's for age's, but he hasnt disclosed any info since he made money remapping ECU's for ither guys. With some proper tuning software this might be an interesting thing to toy around with..
Imagine the benefits for relatively normally modded engines (cams, intake, exhaust), if you could get a proper map for it and run it using the factory ECU, with all the fancy correction factors still in place (possibly modded lightly as well)...
The trouble I suspect lies in making good mappings.

With my system there are no secrets about the mapping.
It is all displayed on the laptop screen for the user.

Maps can be altered by pointing and clicking with the laptop mouse.

Also it is possible to create a date/time stamped report from the ECU on all reprogrammed maps.
It can be printed out and shows before and after changes of any remapping. All the maps that can be reprogrammed will be listed in the report. This includes the rev limiter setting and TVIS setting.

Maps could be compared/exchanged between owners.

Also you can datalog test drives in the car and play back the journey on a viewer program. See http://www.jmross.freeserve.co.uk/page1.html

You could monitor how the fuelling has changed if you datalog 'before and after mapping' test drives.

This datalogging capability will be included with the ECU too. You even get a fuel economy readout on the laptop as you drive the car.

[phatBob]

That is an outstanding piece of work.

I'm interested in acceleration enrichment at this time because its the last part of the fuel setup that I'm doing on a 20v engined AE86. I'm using the VEMS managment system which has configurable enrichment values based on throttle opening speed (although MAP based enrichment is also possible). I'd be very interested in any timing advance information that you may have come across, as a maximum I'm running 25 degrees advance and I'm sure it can use more than that.

Rob

[JMR_AW11]

phatBob Wrote:That is an outstanding piece of work.

I'm interested in acceleration enrichment at this time because its the last part of the fuel setup that I'm doing on a 20v engined AE86. I'm using the VEMS managment system which has configurable enrichment values based on throttle opening speed (although MAP based enrichment is also possible). I'd be very interested in any timing advance information that you may have come across, as a maximum I'm running 25 degrees advance and I'm sure it can use more than that.

Rob

Thanks to everyone for the compliments about the articles etc.

As for the ignition timing, I have worked out the relationship between the 8 bit value and the real timing advance. I keep meaning to update the graphs on my web page to show degrees BTDC.

If you could send me an old 20V ECU I could remove the MCU chip and read out the ROM code from the chip and post the factory ignition map on here if you like.

I've also successfully hacked into the newer ECUs like the 4A-GZE and 3SGTE which use a more advanced family of MCU. I'd imagine the 20V ECU will use one of these newer MCUs so I should be able to read out the ROM no problem.

[NoHachi]

There is an interesting discussion going on about Accel-enrichment on the MS-EFI boards..I always used to believe that it was only necessary because of wall wetting effects and the resulting fuel dump into the intakestream..Some people there suggested a cause related to the pressure differential over the intake and exhaust ports..

Anyway, the end result is having to reference both delta TPS/MAP (depending on what system you run) and rpm...I was wondering whether the same thing happened in the older ecu's.

[firehawk]

On the ignition map, how does the 8-bit value correspond to actual ignition advance in degrees? Is it simple 0.8 fixed-point arithmetic, ie. the advance = max_advance*(cell_value/255)? If this is the case, have you determined what's the maximum advance in degrees (excluding the advance set mechanically from the distributor)?

Edit: man, I should refresh the browser window to see if there has been any more replies since I opened the thread.

You might also be interested in this;

http://www.r5r.net/gallery/album14

It's the TRD Group-A ECU used in circuit racing and rallying in the 80s and we're currently running our AE82 race car with the unit shown in the pictures. It's been build "on top" of the standard ECU similarly as we've discussed here. The piggyback board appears to have, in addition to some standard logic chips, an unknown Nippon Denso CPU (151801-1230? MC6800 clone?), a Hitachi HD46821 PIA (MC6820 clone) and two EPROMs (one marked 001, the other "RALLY4" "84.11.9" "E8" "5985"). I've been itching to dump out the contents of the socketed EPROM to see what I could find in there but my teammate doesn't want me to break our precious ECU.

[JMR_AW11]

firehawk Wrote:On the ignition map, how does the 8-bit value correspond to actual ignition advance in degrees? Is it simple 0.8 fixed-point arithmetic, ie. the advance = max_advance*(cell_value/255)? If this is the case, have you determined what's the maximum advance in degrees (excluding the advance set mechanically from the distributor)?

Edit: man, I should refresh the browser window to see if there has been any more replies since I opened the thread.

You might also be interested in this;

http://www.r5r.net/gallery/album14

It's the TRD Group-A ECU used in circuit racing and rallying in the 80s and we're currently running our AE82 race car with the unit shown in the pictures. It's been build "on top" of the standard ECU similarly as we've discussed here. The piggyback board appears to have, in addition to some standard logic chips, an unknown Nippon Denso CPU (151801-1230? MC6800 clone?), a Hitachi HD46821 PIA (MC6820 clone) and two EPROMs (one marked 001, the other "RALLY4" "84.11.9" "E8" "5985"). I've been itching to dump out the contents of the socketed EPROM to see what I could find in there but my teammate doesn't want me to break our precious ECU.

That is very interesting to see that ECU.
I would imagine one EPROM contains all the program code and one will contain the mapping (the socketed one).

Unless you dump out both EPROMS and trace through the program code you are never going to find out which maps do what. If you ever dump out the EPROMs then I would be keen to see the contents of both EPROMs.

(Unless of course you already have this map info direct from TRD)

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)

BTW
If your ECU ever fails then I could repair it for you.