Twenty Thousand Degrees Advanced

[EagleMark]

Do all 16 bit data have to be signed? Because the BPW is 16 bit and not signed too...

[RobertISaar]

not required of all 16-bit, some 8-bit values are even signed at times.

if there is a value that can go negative and it doesn't have a negative offset in its equation, that is a good indication that it is a signed value. otherwise, you get the whole wraparound issue that happened here. if spark happened 4.9* BTDC, the raw value is 14 (14X.35=4.9). if it happened 4.9*ATDC, the same 14 comes into play, but it is subtracted from 65,535(or 65,536, i can never remember), so 65,535-14 = 65,521.

it's kind of like a compliment situation, except the MSB of the value determines the sign. 0-32,767 is positive and 32,768-65,535 is negative. with 8-bit values, 0-127 is positive and 128-255 is negative.

while the MSB is set(so, things are negative), the scales are reversed(large raw values are actually small real-world values).


it's still kind of confusing to me at times.

[ericburgundy]

You're genius!!!!!
replayed the log with the new ADX, and what was 23000 SA is now -3.867
I have factory spec 4 degrees advance at the distributor. Does the computer factor that in, so in this instance we have 4 ATDC?
With timing that late, I could see the spark jumping to #8 cylinder.... = fireball.

What advance range should we be in with low RPM/WOT/low load?

[ericburgundy]

At warm idle, the data says 10 degrees advanced.
But at the damper checked with a timing light its 4.
I have verified the marks are correct on the damper.
I have set base timing to 4 degrees with ETS disconnected.
Now I should either read 10 degrees with a light if the computer accounts for the base time,
Or 14 degrees if it does not.
Why the discrepancy?