blue86iroc

iTrader: (2)

I've seen people talk about this table for adjusting the injector pulsewidth (obviously), but I was always curious as to how the table actually worked -- how can fluctuations in battery voltage be used in a fuel calculation? Especially considering that the table's VDC goes up to 25.6 volts... car batteries usually don't run THAT high, do they?

RBob

iTrader: (1)

The lower the voltage the longer is takes for an injector to open the less fuel is delivered.

And the higher the voltage the less time it takes to open and more fuel is delivered.

The table compensates for this change in opening time.

Don't know why the table exceeds above and below what you'd normally see in vehicle voltage. It's just the way they did it.

RBob.

Grumpy

Key word, usually.
Short the right combo of diodes out in the alternator, and you can get it. It won't read on a normal meter, but with a good scope you can see it when it happens.

RedIrocZ-28

First hand experience, when your alternator goes dead and you're running on battery power alone, coupled with what RBob said above, can make for a very rough running fuel injected vehicle. This happened to me one time in my bonneville. The battery was near dead and the alternator was DOA. I believe that if there weren't those calibrations for 7VDC and lower my car would have stalled in rush hour traffic. However, it seems like a fail soft mode calibration of sorts.

blue86iroc

iTrader: (2)

Makes sense. Now I understand why a lot of people modify this table to change injector PW globally. Thanks for the replies, RBob, Grumpy, and RedIrocZ.