So this is the suspect routine for dwell calculations.
It relies heavily on low res, old low res, delta low res, ign voltage, rpm and map.
Still have no clue what it does.

Code:
RESERVED:3E0C loc_3E0C:                               ; CODE XREF: OC4I+40Bj
RESERVED:3E0C                 bclr    byte_25 $20 ; ' '
RESERVED:3E0F                 ldd     word_13D
RESERVED:3E12                 lsrd
RESERVED:3E13                 lsrd
RESERVED:3E14                 lsrd
RESERVED:3E15                 coma
RESERVED:3E16                 comb
RESERVED:3E17                 addd    word_13D
RESERVED:3E1A                 bpl     loc_3E1F
RESERVED:3E1C                 ldd     #0
RESERVED:3E1F
RESERVED:3E1F loc_3E1F:                               ; CODE XREF: OC4I+420j
RESERVED:3E1F                 std     word_13D
RESERVED:3E22                 ldd     word_A1
RESERVED:3E24                 std     word_135
RESERVED:3E27                 ldaa    #$FF
RESERVED:3E29                 ldab    word_16B
RESERVED:3E2C                 subb    byte_16D
RESERVED:3E2F                 bcs     loc_3E35
RESERVED:3E31                 cmpb    #$20 ; ' '
RESERVED:3E33                 bcc     loc_3E53
RESERVED:3E35
RESERVED:3E35 loc_3E35:                               ; CODE XREF: OC4I+435j
RESERVED:3E35                 ldd     #$4000
RESERVED:3E38                 cpd     word_135
RESERVED:3E3C                 bls     loc_3E56        ; above 60 rpm
RESERVED:3E3E                 cpd     word_137
RESERVED:3E42                 bls     loc_3E56
RESERVED:3E44                 ldd     word_137
RESERVED:3E47                 subd    word_135
RESERVED:3E4A                 lsld
RESERVED:3E4B                 subd    word_13D
RESERVED:3E4E                 bmi     loc_3E56
RESERVED:3E50                 addd    word_13D
RESERVED:3E53
RESERVED:3E53 loc_3E53:                               ; CODE XREF: OC4I+439j
RESERVED:3E53                 std     word_13D
RESERVED:3E56
RESERVED:3E56 loc_3E56:                               ; CODE XREF: OC4I+442j
RESERVED:3E56                                         ; OC4I+448j ...
RESERVED:3E56                 ldd     word_16B
RESERVED:3E59                 std     word_16B+1
RESERVED:3E5C                 ldd     word_135
RESERVED:3E5F                 lsrd
RESERVED:3E60                 lsrd
RESERVED:3E61                 lsrd
RESERVED:3E62                 cpd     word_13D
RESERVED:3E66                 bcc     loc_3E6B
RESERVED:3E68                 std     word_13D
RESERVED:3E6B
RESERVED:3E6B loc_3E6B:                               ; CODE XREF: OC4I+46Cj
RESERVED:3E6B                 ldd     word_135
RESERVED:3E6E                 std     word_137
RESERVED:3E71                 ldd     #0
RESERVED:3E74                 brset   byte_23 $80 loc_3E7B ; 'À'
RESERVED:3E78                 ldd     word_2048
RESERVED:3E7B
RESERVED:3E7B loc_3E7B:                               ; CODE XREF: OC4I+47Aj
RESERVED:3E7B                 std     word_145
RESERVED:3E7E                 ldab    byte_128
RESERVED:3E81                 cmpb    #$2D ; '-'
RESERVED:3E83                 bcc     loc_3E87
RESERVED:3E85                 ldab    #$2D ; '-'
RESERVED:3E87
RESERVED:3E87 loc_3E87:                               ; CODE XREF: OC4I+489j
RESERVED:3E87                 subb    byte_204B
RESERVED:3E8A                 clra
RESERVED:3E8B                 xgdx
RESERVED:3E8C                 ldd     word_204C
RESERVED:3E8F                 idiv
RESERVED:3E90                 ldd     word_135
RESERVED:3E93                 cpd     word_204E
RESERVED:3E97                 bhi     loc_3EB1        ; bra below 3400 rpm
RESERVED:3E99                 ldd     word_204E
RESERVED:3E9C                 subd    word_135
RESERVED:3E9F                 lsrd
RESERVED:3EA0                 adcb    #0
RESERVED:3EA2                 adca    #0
RESERVED:3EA4                 std     word_143
RESERVED:3EA7                 xgdx
RESERVED:3EA8                 subd    word_143
RESERVED:3EAB                 bcc     loc_3EB0
RESERVED:3EAD                 ldd     #0
RESERVED:3EB0
RESERVED:3EB0 loc_3EB0:                               ; CODE XREF: OC4I+4B1j
RESERVED:3EB0                 xgdx
RESERVED:3EB1
RESERVED:3EB1 loc_3EB1:                               ; CODE XREF: OC4I+49Dj
RESERVED:3EB1                 stx     word_13F
RESERVED:3EB4                 ldd     word_135
RESERVED:3EB7                 lsrd
RESERVED:3EB8                 lsrd
RESERVED:3EB9                 lsrd
RESERVED:3EBA                 lsrd
RESERVED:3EBB                 std     word_A3
RESERVED:3EBD                 addd    word_145
RESERVED:3EC0                 addd    word_13D
RESERVED:3EC3                 addd    word_13F
RESERVED:3EC6                 std     word_13B
RESERVED:3EC9                 ldx     word_2052
RESERVED:3ECC                 ldaa    byte_160
RESERVED:3ECF                 cmpa    byte_2050
RESERVED:3ED2                 bls     loc_3EDF
RESERVED:3ED4                 ldaa    word_16E
RESERVED:3ED7                 cmpa    byte_2051
RESERVED:3EDA                 bls     loc_3EDF
RESERVED:3EDC                 ldx     word_2054
RESERVED:3EDF
RESERVED:3EDF loc_3EDF:                               ; CODE XREF: OC4I+4D8j
RESERVED:3EDF                                         ; OC4I+4E0j
RESERVED:3EDF                 stx     word_143C
RESERVED:3EE2                 pshx
RESERVED:3EE3                 tsx
RESERVED:3EE4                 ldd     word_135
RESERVED:3EE7                 subd    0,x
RESERVED:3EE9                 pulx
RESERVED:3EEA                 cpd     word_13B
RESERVED:3EEE                 bcs     loc_3EF3
RESERVED:3EF0                 ldd     word_13B
RESERVED:3EF3
RESERVED:3EF3 loc_3EF3:                               ; CODE XREF: OC4I+4F4j
RESERVED:3EF3                 std     word_139
RESERVED:3EF6                 std     word_141C
RESERVED:3EF9                 subd    word_A3
RESERVED:3EFB                 cpd     word_13F
RESERVED:3EFF                 bls     loc_3F04
RESERVED:3F01                 ldd     word_13F
RESERVED:3F04
RESERVED:3F04 loc_3F04:                               ; CODE XREF: OC4I+505j
RESERVED:3F04                 std     word_141
RESERVED:3F07                 bne     loc_3F0C
RESERVED:3F09                 ldd     #1
RESERVED:3F0C
RESERVED:3F0C loc_3F0C:                               ; CODE XREF: OC4I+50Dj
RESERVED:3F0C                 std     word_1440
RESERVED:3F0F                 brset   byte_23 $80 loc_3F40 ; 'À'
RESERVED:3F13                 ldd     word_139        ; at eng off
RESERVED:3F16                 ldx     word_135
RESERVED:3F19                 fdiv
RESERVED:3F1A                 ldaa    #$B4 ; '+'
RESERVED:3F1C                 pshx
RESERVED:3F1D                 tsx
RESERVED:3F1E                 psha
RESERVED:3F1F                 ldab    1,x
RESERVED:3F21                 mul
RESERVED:3F22                 adca    #0
RESERVED:3F24                 pulb
RESERVED:3F25                 psha
RESERVED:3F26                 ldaa    0,x
RESERVED:3F28                 mul
RESERVED:3F29                 tsx
RESERVED:3F2A                 addb    0,x
RESERVED:3F2C                 adca    #0
RESERVED:3F2E                 ins
RESERVED:3F2F                 pulx
RESERVED:3F30                 adda    byte_14B
RESERVED:3F33                 tab
RESERVED:3F34                 ldaa    #$B4 ; '+'
RESERVED:3F36                 adda    byte_2044
RESERVED:3F39                 sba
RESERVED:3F3A                 tab
RESERVED:3F3B                 lsrb
RESERVED:3F3C                 clra
RESERVED:3F3D                 std     word_14CE
RESERVED:3F40