TBI to MPFI swap questions

[93V8S10]

Unless you wind-up with a problem, then I would say that one wrong offset is just as good as another wrong offset, so stay with what you've got.

I wish I could explain the importance of the offset table, but I just bairly understand it myself, and its been a long time since I was trying.

[1project2many]

The injectors are electromagnetic devices. When the voltage changes, the injectors respond in a different way. Lower voltage means the injectors take longer overall to open. Higher voltage means the injectors respond quickly. So if the VE table currently requires 5 ms injector on time, and the injector takes .01 ms to open at 14 volts, then you've got to command 5.01 ms of injector on time to get 5.0 ms of fuel delivery. Now if voltage drops for some reason, say all the electrical accessories are on, and system voltage drops to 12v from 14, the injector may require .06 ms to open. With no voltage correction this means you've lost .05ms of fuel and the system will be slightly lean until INT / BLM can catch up. But with a good set of voltage corrections the extra time is added to the BPW value so the amount of fuel delivered by the injector remains unchanged.

This can get really obvious in a car where the voltage drops near idle. It's harder to tune, the VE seems all over the place, and each time you think you've got it tuned a small drive will change everything. The solution is to tune the voltage corrections.

If you don't have voltage corrections then no worries, they're easy to work out. Set all numbers in the voltage correction table to zero. Idle the engine (fully warmed up) and confirm about 14V on ALDL data. It's possible to connect a battery charger while the engine's running to increase system voltage at idle. Adjust VE so your INT and BLM are very close to 128 at idle. Disconnect the alternator and remove the battery charger (if used) so system voltage starts to drop. Watch INT. It will start to increase. As the system voltage approaches an entry in the voltage correction table, increase that number so INT moves back to zero. System voltage will continue to drop and you can keep adjusting the table entries in the correction table to bring INT and BLM in line.

The beauty of doing this is it takes into account the behavior of the entire system, not just the injectors, as system voltage drops. Once this table is set up there's no need to mess with it again unless you make changes to the injector wiring or change the injectors.

[JeepsAndGuns]

Good info! I think I understand it now.
Thanks