Duk, thanks for this information, although I'm now somewhat concerned about how much latitude the Motronic will be able to handle even with a remapped ECU.
What can I expect from a remapped ECU? I certainly don't want to lose all of the good stuff (technical term) but I want the Motronic to be able to recognize 'slightly' oversized injectors. I would think that even if I don't have Spruell modify his 10.5:1 TS pistons to 10.3:1 would that be a big deal with a remapped ECU?
Ahhh! Proper remaps are the ONLY way to go (within the capacity of the ECU) if you plan to retain the factory computer. There are other ways, but we'll keep that for a different day.
What people need to understand is that there are fuel and ignition maps inside the factory ECU in the same way there are fuel and ignition maps inside an after market ECU. There is, however, a rather different approach in their 'internal lingo' in the way they tend to intemperate certain stuff, particularly engine load.
When a car manufacture/ECU supplier (like Bosch) tune a/their computer, they calibrate the processors interpretation of various sensor's data and change the fuel and ignition maps. What they ABSOLUTELY DO NOT DO
is fiddle externally with sensor values or fuel pressures to get their desired results. And it doesn't matter who's marketing says what (No one here on the AlfaBB, but there are a few aftermarket controller makers that make such claims) about that.
Car manufacturers get right inside the coding in their ECU's.
This can also be done by those who truly
know what they are doing. Fortunately there are people in the world who have figured out what is going on inside the ECU. Actually, they have been able to look at the raw Hex code in the ECU 'chip (stupid word)' and figure out what parts of the code do what. That is, what lines of the code represent the fuel maps and the ignition maps (amongst a whole bunch of other stuff!).
Real tuners who want to change fuel and ignition timing at given rev and load points do so by changing the appropriate information inside the Hex code.
That way, 1 breed/brand/model of computer could be used to run an engine from the lowliest shopping trolly to a very decent performance car all because of what is programmed into the 'chip (still a stupid word)'.
*** The 'chip' in older computers (car ECU's haven't had them for 10+ YEARS) is called an EPROM. 2 translations of that are: Erasable/Programmable Read Only Memory or Electronically Programmable Read Only Memory.
On the 'chip' is all of the data that tells the processing unit how to interpret the data from the various variable voltage or variable resistance sensors, how to calculate engine speed and position via the crank/cam angle/engine position sensor(s) and what to do in all of the myriad of combinations of engine speed, load, engine temperature, air temperature, knock sensor feedback, EGO sensor feedback and others. It will also contain the data for the 'self learn' corrections that are applied.***
If you want to have a good look at how Nissan ECU work, have a look at ECU Tuning
. You can learn how involved factory ECU's are.
For some offline (not real time) tuning software for Nissan ECU's, go to z31.com | Nissan PROM tuning
and download Live Edit.
Now obviously this is not applicable to Alfa Romeo's and Bosch ECU's, but it can help people learn what is going on inside their ECU. If you can get your hands on the software for an EPROM read/programmer like the Darkwire stuff, then you can actually look at the Hex code in the Nissan ECU files that come with the Live Edit software.
Live edit won't let you change certain things in the Nissan coding. In particular, it won't let you change the 'airflow meter limits'. What lots of people call the 'over boost fuel cut'. It's not a fuel cut and it's not based on boost pressure. What it is, is a 'potentially faulty condition' that causes the ECU to dump extra fuel into the engine and retard ignition timing if the airflow meter shows 'to much air flow' (to high an AFM voltage at a given rev point. That will happen when the boost is wound up in turbo cars). These changes can be made in the raw Hex code IF you know where to look!
Why any mention of Nissan stuff? Well I do believe that the very early digital Nissan ECU were based on early Bosch digital systems. Probably not applicable directly to Bosch stuff, but given the sheer lack of REAL info out there (at least in English), and a very good aftermarket support for a the popular Nissan's, you've gotta get your info and education from where you can