When I installed the standalone ecu to my pickup, I had a running and functioning stock ecu (box tuned) engine. The running engine was my "simulator" for say.
So from that point I began to "piggy back" the new ECM begining from crank and cam signal.
Once it was obvious that was correct, connected a single injector, and setup correct driver voltage and current while exactly comparing to the stock ecu.
At the same time I could log injection timing and populate the timing table making a direct copy of the "box tune".
Pressure control.....I let the new ecu see pressure and control a volume control valve that was not on the actual pump and again monitored output between new and old system and this let me get....."close enough for startup"
Injector conversion table!!! I have flow data for my injectors and populated the table from extrapolating the data. Ideally the more accurate this is the easier the rest of the tune becomes.
Then it was as simple as connect the injectors and turn the key and it was running.....kind of non-dramatic.....
Then could work on the fine tune.
THIS was cheating really....I can see where adapting common rail to a older engine platform say this Detroit and starting right from scratch would be much more difficult!!!
I don't want to crap up your thread here but here's a quick video that I took not to long ago working on a new transmission. I should note the rail pressure is not accurate, it is closer to 30k as I run a pressure sensor the guage is not calibrated to.