Avance - Motronic

 

 

 

Résumé des MotronicType

 

Offset (Decimal)

Offset (hex)

Offset Angle
(in Degrees)

Resolution

ML1.1,  ML1.2  &  ML2.1

0

00h

90º / Tooth#

ML3.1

20

14h

1800º / Tooth#

90º / Tooth#

60-2 roue dentée

30

1Eh

22.5°

0.75º

60-2 roue dentée [MP9.0]

60

3Ch

45.0°

0.75º

60-2 roue dentée

90

5Ah

67.5°

0.75º

 

 

Ignition Advance Formulas - ML1.1, ML1.2 and ML2.1

Ignition Advance Angle = 360º x Hex# / (4 x Tooth#)

Ignition Advance Angle  =   (90º x Hex#) / Tooth#

Tooth#
Hex# = Map value to be converted to ignition angle 
Offset = 0

ML1.1 - The first of the BOSCH Motronic family ECUs first appears in 1982.     This "first generation" of Motronic ECUs had no capability of ignition advance below Top Dead Center.   No negative numbers. The angular rotation of the engine is determined by counting the teeth on the flywheel's ring gear.

 

Quarter Tooth Technology - Each ring gear tooth is counted as 4.  A130 tooth ring gear has a resolution of 4x130 or 520.    Resolution of 360º/20 = 0.6923°. This changes with different ring gears.

Starter Ring Gear - Porsche 944 Flywheel

Car Type

Flywheel Teeth

Map values

Motronic Types

 

944

130 teeth

0.6923°

ML1.1, ML1.2, ML3.1

944Turbo

132 teeth

0.6818°

ML3.1

911

129 teeth

0.6977°

ML3.1

BMW

116 teeth

0.7759°

Various

Volvo

116 teeth

0.6338

ML1.2

 

Ignition Advance Formulas - ML3.1

Ignition Advance Angle = (360º / ( 4 x Tooth# )) x ( Hex#  -  20 )

Ignition Advance Angle = ( 90º /  Tooth# ) x ( Hex#  -  20 )

Tooth#
Hex# = Map value to be converted to ignition angle 
Offset = 20

ML3.1 - Next generation of Motronic ECUs first appears on the 1984 Porsche 911.    Negative numbers appear for the first time.  An offset of decimal 20 [14h] is defined as  0º ignition angle.

 

 

Ignition Advance Formulas - Motronic with 60-2 timing wheel

Ignition Advance Angle Formula = (360º / (4 x Tooth# )) x  (Hex#  -  30)

Short Version 1 = 0.75º x (Hex# - 30)

Short Version 2 = (0.75º x Hex#)  - 22.5º

Tooth# = 120 [for all 60-2 timing wheel]
Hex# = Map value to be converted to ignition angle 
Offset = 30   [In this example]

M1, ML4.1, M2.1 etc. The starter ring gear was abandoned.  A standardized "60-2 timing wheel" was introduced.

 

Changes...

 

Microcontroller from 8051 based to 8052 [or equivalent]

 

standardized "60-2 timing wheel"

 

offset of 30 [1Eh] is now defined as  0.0º  ignition angle.

 

Minimum ignition advance 22.5°

 

1h = .75º

 

 

The 60-2 timing wheel

 

In the mid 1980's Bosch standardized on this dedicated timing wheel with 60 equally spaced teeth. A single sensor is used. Since the teeth are equally spaced, both the leading edge and falling edge are now counted. This gives a total of a 120 count [triggered events] per 360º revolution.   Two teeth are missing  and this indicates the location of top dead center.

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