how many cycles per second does the stock ECU operate at? i am going to try to hook up one of my spares to the PC in hopes of simulating engine conditions by faking sensor inputs and logging ECU outputs, thereby giving us a detailed map of ECU programming. after that i will use the logs to create my own programming and try to run an engine from my laptop.

what is the most basic control i need over an engine to make it run? (just at an idle) i need to be able to fire injectors and spark plugs. is that all? meter air, add appropiate amount of fuel, fire ignition at proper time.
that about sum it up? does anyone know what kind of accuracy i need on the crank sensor? the lead timing is at 5 degrees after top dead center. trailing is 20 deg ATDC.

alternator output is 12v at 70amps? i suppose i will need a transformer to power my ecu for testing purposes, eh? or else hook it up to a car battery. i guess running the ecu cant use that much power. hehehe

so if i can accurately track the crank (via CAS output)
then i should be able to dump in some gas by giving the injectors power and telling the ignition coils to fire at the specified crank position. even without giving it the RIGHT amount of gas it should at least TRY to run. hehehe.

the FSM looks like its got enough info here for me to fake all the sensor output i need, so i guess i can just give it a whirl and find out just how fast the ECU is on my own.

if anyone can give me a list of exactly what functions a good ECU should perform, it would be most appreciated.
like ignition advance with rpm, retard with boost, more fuel with load, ignition retard on decel... whatever.
anything the haltech does i want to hear it. hehe
thanks.

 

people already have full ecu maps ect on there computers... read straight off the ecu chip. but it doesn't go anywhere... reted tryed to do a bunch. there is also somebody else right now who has some big electrics board made hooked up to an ecu testing stuff.

and the ecu is slow...

 

well hell! why doesnt everyone have this information?
or am i just the last to hear about it. =)

know where i can get my hands on one?

hahaha, slow... =) good i was worried it would be blazingly fast and i wouldnt be able to keep up.

slow makes things easier

 

S4 NA ECU:
8-bit, 16Kb processor, 52 digital terminals
Inputs: vehicle speed, throttle position, exhaust manifold pressure, air flow, coolant temperature, engine rpm, exhaust gas O2.
Outputs: spark timing, fuel injection, idle speed, exhaust emission.

S5 ECU:
Supposedly twice as fast.

Sorry, I don't know what all is required to trick the computer into working. IMO, it is best to throw it in the trash and buy an aftermarket EMS made in the current century.

 

how is idle speed and exhaust emmision an output function of the ECU?

seriously good information.

8 bit, eh? w00t NES!!!

exhaust manifold pressure??? are you serious?
what the heck for?

 

I'm not exactly sure what you're trying to do...

You mention clock speed, but do you know there's a difference between CPU clock speed and uP clock speed?


-Ted

 

The base idle speed is controlled by the TB, but the ECU uses the BAC valve and ASV to increase idle speed to compensate for alternator, air-con and power steering loads.
Emissions output is controlled by the ECU-controlled secondary air injection system, EGR system, etc.

 

Vash,

I've done some similar work in the last couple weeks. I have installed the MegaSquirt standalone EFI system on my '86 n/a. I modified the stock ECU, and diverted the appropriate inputs and outputs to the MS to allow it to run injectors. Ignition is still run by stock ECU. To check tuning values I'm using, I've compared the stock ECU's pulse width against my present MS settings. This has been quite helpful. I have configured the system so I can quickly swap back to a spare stock ECU if I have problems with my 'experimental' setup.

 

what is uP clock speed?

the speed i was thinking of is how many times per second the computer analyzes all input and computes new values for output.

oooh right. i shoulda thought of that. im sitting here with no emmisions controls on my car so i totally forgot about them. hehehe

 

It's not faster than 12MHz.

Clock speed comparision with a (computer) CPU isn't valid, since the reduced IS of the uP and the fact it runs in machine langauge (well the CPU does to, technically) allows very quick absolute time frames for an instruction cycle...



-Ted

 

The stock 86-88 ECU is a modified 6303 running at 1MHz, this gives it about a 300k instructions/s execution rate - quite slow particularly these days (shift all decimal points by 3!). How it works is a mix of software with hardware support. Basically all the timing critical stuff (injection timing/length, ignition timing) is handled with hardware assist - you won't be able to duplicate this affect easily with S/W only (needs lots of SW cycles). The main loop runs at 8.2ms, which allows it to handle up to about 7300rpm (probably one reason why the redline is at 7k). Don't let its lack of advertised blazing speed fool you, the outputs are plenty accurate - fuel can be controlled to the uS as an example. Haven't figured timing yet. The 89+ runs at 1.5MHz I believe (somebody give me one and I'll confirm

BTW the stock ECU does all those things you mention in the "what a good ecu does" category, it just has a different optimization than many people with aftermarket ECUs are running.

Also, starting and idling an engine are probably the hardest things to do - WOT is much easier.

Henrik
87TII

 

www.16paws.com

mike