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4age - ecu, how does it work?
Hi guys,
A friend of mine in antarctica wants to know something about stock, bigport 4AGE ECU's.
How exactly do they *work*? Do they use the 02 sensor until XX amount of throttle or XX amount of revs are met, then switch to a pre-set "map"? Or do they use a pre-set map all the time?
Do the ECU's "learn" or are they "adaptive"?
Gurus feel free to join in.
fuzzy logic
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I haven't played with them extensively, and there are probably a few souls around better equipped to answer, but from what I've read/seen/heard:
The O2 sensor is only used at cruise (low throttle, reasonably constant RPM). There is it used to add/remove up to 5% fuel to keep the desired AFR. When giving it some gas the ECU uses open loop control, where it just looks up injector times in a table and uses them.
I'd be surprised if they were using any adaptive control or serious "learning" in an ECU from the mid-late 80s.
Hen
No adaptive learning
O2 sensor only works in light load cruise, tries to keep it at stoich for max cat efficiency
ecu's using knock sensor have 2 ignition maps
early ecu's 8 bit, later 16bit
Hachiroku since 1994
Originally Posted by LittleRedSpirit
I have a article on a guy who reverse engineered an AW11 4age ecu. Basically has pre-defined maps and alters those maps based on sensors (richer/leaner). So e.g. based on AIT, it will +/- 5% blah blah.
He was trying to do what the honda and nissans guys have with retuning there ECU. Aparently toyota's aren't as easily cracked.
I'll try to refind it an post it. interesting stuff.
Yeah please do, that stuff is always interesting, if you can read Japanese try and track down a book written by the founder of E&E Systems, he did the Freedom computer. I have had a few bits a pieces translated and it's great stuff.
Hachiroku since 1994
Is that 'Sam' by any chance? (Razorback)
Interesting info so far guys, thanks!
yer i wouldnt mind a copy of that article too!
as for the 4age ecu. pretty primitive, but same as most standard ecus.
they can simplifiy it right down since they dont expect you go to and change things.
ive gathered the following about the 4age ecu.
the ecu fires the injectors in a "batch" style. ie all the injectors fire at once. im not exactly sure when they do it, but they arent done sequentially. however the spark plugs are fired sequentially (individually) when required for each cylinder.
the basic fuel and spark map is based around a fuel/spark table, with MAP sensor on one axis, and RPM on the other axis. its very simple, the ecu detects both of these values, and this lines up pulse opening time for the injectors (in mili seconds). and the same thing is done for the spark table, the amount of spark advance is found, and then on the next cycle it is implemented. the map sensor is basicaly sensing "load" on the engine, and the rpm well its exactly what it is.
im not sure of the polling time of the 4age (how many times it "checks" the sensors) but it woudl be pretty high..
now that is enough to get your base map going well. now onto the enrichments.
the tps, when you slam down the throttle the ecu gives an enrichement percentage to the base map. it also lets the ecu know that you want the engine to get up and go, which im not exactly sure how it does it, but you get better throttle response. you will find that if you unplug the TPS, your throttle response will be lower, and also when you jump off the throttle the revs will not drop as quick. i guess the tps is just an extra input that the ecu uses to detect exactly what you want out of the engine. the MAP sensor can be a bit "laggy" since its detecting pressure changes in the manifold, which dont perfectly correlate to what your doing with your right foot (although it is good enough to make it run very well). the tps just gives it that extra edge.
now onto other sensors. the green temperature sender (from what i understand) applies an enrichment across the entire fuel map, when the engine is cold. ie to make driving a cold engine a little bit easier. it also tells the ecu when the engine is hot (obviosly) so it can apply the best fuel mixture and spark advance to make the most power. you will find that if your temp sensor is stuffed (like mine was) it will run rich all the time, and when you slam your foot down it will stumple and splutter and carry on. essentially its just over fueling.
right now onto the cold start injector, my understanding is that the brown plug is just a temperature switch, and when its cold the cold start injector fires with all the other ones. just to give that extra fuel when you are trying to start the engine. pretty sure thats how it works.
now there arent that many more sensors on the ye ol 4age...
as said the 02 sensor works to give the optimal AFR on cruising, gets those lovely low fuel usage figures on the highway. one of the reasons is that the standard 02 sensor (like most cars) is a "narrow band" sensor. this means that it takes around 10 secs for it to read the air fuel mixture proply (well the exhaust end of it). so this is why its only good for cruising. alternatively you can get a "wide band" 02 sensor, which is used by ecus that auto tune on the fly, and also used by tuning shops when tuning your car. these react to the air fuel mixture much quicker.
there is also the air temp sensor, this is used to (you guessed it) detect the air temp, essentially colder air = more dense air = more air particles = more fuel required.
thats about it really....
i dont think ive mised anythign important
In faith there is enough light for those who want to believe and enough shadows to blind those who don't.
- Blaise Pascal
Narrow band O2 sensors work on a 0-1v and works in a "narrow" band, it is designed to work around stoichiometric a/f ratio, it doesn't work very good outside of this range
you can see from the diagram below that either side of stoichiometric gives a voltage which is about the same, this means when using a narrowband sensor what is a "rich" voltage?? By this I mean, look at anything richer than 14.7:1 and have a look at the voltage....it's about the same!! If you are lighting up LED's using this voltage, how rich is your mixture? really rich(11.0:1) or 13.0:1?????
This is still a fast reading sensor just not really designed to work off stoich, all it will say is YES richer/leaner than stiochiometric.
A wideband or linear sensor gives a voltage for each a/f ratio(in easy terms)they generally work on a 0-5V output
This is the only type of sensor used with an a/f ratio meter I would EVER use for tuning!
It is not uncommon these days to find an upstream and downstream O2 sensor, used like this they are checking cat converter efficiency, contrary to popular belief the MAIN reasons for having an O2 sensor is to maintain a stoichiometric a/f ratio(in light load/cruise) so that the cat converter gets maximum conversion, a by product is better fuel efficiency, if you were aiming strictly for max economy in light light you would use in the 15's or even leaner BUT then oxides of nitrogen start to go through the roof.
Last edited by Frak; 27th July 2009 at 10:12 PM.
Hachiroku since 1994
ahh good info frak, that makes sense.
interesting point about the cat convertor being used to its maximum, i never realised that.
In faith there is enough light for those who want to believe and enough shadows to blind those who don't.
- Blaise Pascal
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