[Gmecm] Modify $8D to work on MPFI 3.1L DIS engine - It RUNS

[davesnothereman at netscape.net]

Changing calibration values does not generally cause communication failures.  Changing spark reference angles may cause engine failure, but does not cause ECM comms failure.
 
Timing values for max and min work like number line.  Look at absolute value for conversion to degrees.  For negative ($FFXX) values, use difference between $10000 and value in question.  Sign for "advance" or "retard" depends on spark reference angle and sign of spark typically encountered after reference angle is subtracted from desired angle.  
 
 $10000
-$ FFE3
=$   1D
 
$1D = d29
d29 * .35163 = 10.195
 
Generally speaking, for DIS calibration, typical spark angle has negative sign.  More negative values indicate more advance.  For distributor calibration typical spark angle has positive sign.  More positive spark values indicate more advance.  The $88 data posted indicates 60 deg maximum advance and negative 10 deg minimum advance.
 
Zaphod
 
-----Original Message-----
From: bpatten at centurytel.net
To: gmecm at diy-efi.org
Sent: Mon, 4 Sep 2006 1:38 AM
Subject: RE: [Gmecm] Modify $8D to work on MPFI 3.1L DIS engine - It RUNS


Here is what I have found.

1990 CAVALIER Z24 ATMF5241 $88
            location        hex     value 
Initial SA:     13          1A      9.14
Spark Ref Angle 15          AA      59.77
        Equation:  0.351563 * X + 0 used for two above

Max Adv     1D          FF E4       -19.69
Max Retard      1F          FF 39       -139.92
        Equation:  0.703125 * X + -46080.000000 used for two
above

All this data looks correct for a DIS v6 engine.  I looked at my
Tunerpro XDF definitions and the A1, 8F, 88 all have the exact same
values for those 4 constants.

Now here is the 88 mask 3.1L Camaro distributor

AZTY1407 FBODY 3.1L $88
Initial SA:     13          1A      9.14
Spark Ref Angle 15          1C      9.84
        Equation:  0.351563 * X + 0  same equation as above DIS
motor, same values seems logical.

Max Adv     1D          00 AB       -45956.77
Max Retard      1F          FF E3       -20.39
        Equation:  0.703125 * X + -46080.000000 same as used
above.

Now what happened to the Max Advance????  If you use the 0.351563
equation, you get a number that makes more sense.  60.12 Degrees.

So what is going on here???
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