[Diy_efi] pic based afm -> maf conversion

[Ashley Evans]

Daniel R. Nicoson wrote:
> Honestly?  With some of the stuff you are proposing, I think you'd be
> further ahead trying to read the bin file off the BMW ECU and figure out all
> the settings there.  Then modify the fuel tables, spark tables, airflow
> functions, and write this info back to the ECU.  What you are proposing in
> all this discussion so far is modifying inputs to achieve outputs.  Problem
> with that is you don't really know what the ECU does with all that.
>   
> One example:  You mentioned adding a lean-burn cruise mode.  I assume you
> intend to tell the ECU there is less air than normal so it cuts fuel back =
> lean.  That would be good except for cruise is typically a closed loop
> operation.  Not sure how old your ECU is (do tell) but since the mid 1980's
> most ECU's run closed loop at cruise which means they look at the calculated
> air coming in, factor in other things like RPM etc, command a pulse width
> and then check the result (O2 sensors).  Now if they detect a bit of
> leaning, the ECU modifies its short term fuel trim table and starts the loop
> again, this time zeroing out your recently added "lean input".
>
> So by just modifying the inputs, you won't achieve long term success.
> Without control over the actual code, tables, functions and scalars, most of
> your proposed mods will not work.
>
> This post is not meant to discourage you in your quest to make the BMW
> better.  I would first research how much is known about the actual operating
> logic for this particular ECU.  I think the older Motronic ECU's may have
> some hacker groups out there, find them, learn as much about the various
> modes of operation, then consider what some of these "input mods" will
> really do.
>
> Dan Nicoson
>   

I've yet to come across anybody who really know the inner workings of 
these motronic systems unfortunately.  I still keep my eyes open for it 
though.  Some people know where to modify in the .bin for fuel/spark and 
rev limit but they tend to be cagey about releasing this information as 
it's part of their revenue stream.  Also there are some books available 
on motronic, I suppose it should invest.

Most e30s in this country came without a CAT, mine included,  so there's 
no O2 sensor on the car.  This doesn't mean that there won't be other 
unknown signals that have an effect on the fuelling, besides the air 
meter. Hopefully there won't be but I'll have to see how things pan out 
when I get to install the first revisions.

For those intersted it's motronic 1.3 (55pin) system. 

No discouragement taken.  There are many ways to modify a car, some are 
"the right way" and others are a bit hackish.  This is obviously the 
latter but, I still think it has scope to improve the car 
significantly.  Of course as the project extends out of just the air 
metering, I'll look at taking control of other sensors maybe eventually 
replacing the ECU altogether, but time will tell on that one.

Cheers,
Ashley