More silly ideas-MAP

[Ludis Langens]

JTesta1966 at aol.com wrote:
> 
> This may be a stupid question, but I KNOW Fords do this (I went for ford
> training YEARS ago), doesnt the ECM look at MAP KOEO prior to starting to get
> a baro reading? And the compensate off that? Are you trying to have something
> constantly adjust for atmospheric changes??

Some GM ECMs do constantly update the baro reading based on other
sensors.  Here is a code snippet from the 1227170 ECM:

(first some calibration data)

CalcBAPMaxRPM   RPM     3600rpm
BAPDefault      RawMAP  95.9KPa
BoostBAPDefault DC.B    98
bap_a           DC.B    51
bap_b           DC.B    96,109,122,134
bap_c           DC.B    16,48,6
                DC.B     9, 7, 6, 1, 0, 0 ;1200 RPM
                DC.B    35,16, 8, 3, 3, 0 ;2400
                DC.B    68,38,21,11, 8, 8 ;3600

(now the program code)

                LDAA    EngineRPM
                CMPA    CalcBAPMaxRPM
                BHI     @6
                BTSTA   FeatureFlags,#twoBar
                BNE     @9
                LDAB    AccelThrottle
                SUBB    Throttle
                BHS     @2
                NEGB
@2              CMPB    #3
                BHS     @6
                LDAB    OneBarMAP
                CMPB    Barometer
                BHI     @0
                LDAB    Throttle
                CMPB    #96
                BLO     @6
                LDAA    EngineRPM
                CMPA    #1200/25
                BLO     @6
                CMPA    #3600/25
                BHI     @6
                LSRB
                PSHB
                LDAB    #85
                MUL
                BCC     @3
                INCA
@3              PULB
                LDX     #bap_c
                JSR     ArrayLookup
                CMPA    bap_a
                BLS     @4
                RTS
@4              PSHA
                JSR     BarometerIndex
                LDAB    #96
                LDX     #bap_b
                JSR     DifTableLookup
                PULB
                MUL
                ASLD
                BCC     @5
                LDAA    #255
@5              LDAB    OneBarMAP
                ABA
                BCC     @8
                LDAA    #255
                BRA     @8
@6              LDAA    BoostBAP
                BNE     @7
                MOVA    BoostBAPDefault,BoostBAP
@7              LDAA    Barometer
                BNE     @9
                LDAA    BAPDefault
@8              STAA    Barometer
@9              RTS

>From the above, you'll see that between 1200 and 3600 rpm, at moderate
(ie 96) to WOT steady (+/- 2) throttle, the baro value might be updated.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/