M50 Engine

M50 Engine

Information on the BMW M50 Engine.








General Information

Cylinders
6
Displacement

B20 1991cc (121ci)

B24 2394cc (146ci)
B25 2494cc (152ci)
B30 2990cc (182.5ci)
B32 3201cc (195.3ci)
Firing Order
1,5,3,6,2,4





Model Variants

There are a number of variants of the M50 engine.  TU models refer to "Technical Update" and added single VANOS to the intake cam.  S50 variants are listed as a Model Vairant but they not covered in this guide. S-engines are high performance versions of M-engines.

M50B20

10.5:1 comp. iron block, alluminium head, 6500rpm limit

M50B20TU

1992-on, Single VANOS, 11.0:1 comp

M50B24TU

Thailand Only, 10.5:1 comp, same as B25TU but with reduced stroke

M50B25

10.0:1 comp

M50B25TU

1992-on, Single VANOS, 10.5:1 comp

S50B30

10.8:1 comp, 6x throttle intake, exhaust changes, 7200rpm limit

S50B32

1996-on, 11.3:1 comp, Dual VANOS, 6x throttle intake, 7600rpm limit, 3x knock sensors





Common Models

Engine Type
Common Vehicles
M50B20
  • 1990-1992 E34 520i
  • 1991-1992 E36 320i
M50B20TU
  • 1992-1994 E36 320i
  • 1992-1996 E34 520i
M50B24TU
  • 1993-1995 E36 325iA/2.4
  • 1992-1996 E34 525iA/2.4
M50B25
  • 1990-1992 E34 525i, 525ix
  • 1991-1992 E36 325i, 325is
M50B25TU
  • 1993-1995 E36 325i, 325is
  • 1992-1996 E34 525i, 525ix






Sensor Information

Crank/Cam Sensor

This engines uses a Crank Position Sensor with the trigger wheel having 60x teeth with a 2x tooth missing gap, commonly known as a 60-2.  This is part of the crank pulley on the front of the engine.




The cam trigger has a single tooth ring bolted to the end of the camshaft.  Both Reluctor and Hall Effect sensors were used on different models.  Early non-VANOS models use a Reluctor sensor, and later VANOS models use a Hall Effect sensor.

Reluctor cam trigger ring



Hall Effect cam trigger ring







Crank Sensor

A Reluctor crank position sensor is used and is located on the front of the engine.




Resistance between terminals 1 + 2 should be around 540 ohms.   1mm air gap to triger wheel.

Looking into sensor connector


Wiring

Sensor Pin
Function
Haltech Connection
1
Signal +
Trigger+ Yellow in Trigger 4-core
2
Signal -
Trigger- Green in Trigger 4-core
3
Shield
No Connection



Early Non-TU Cam Sensor

A Reluctor cam sensor is used on non-TU models. 




Non-TU Cam Sensor Wiring
Sensor Pin
Function
Haltech Connection
1
Signal -
Trigger- Green in Trigger 4-core
2
Signal +
Trigger+ Yellow in Trigger 4-core
3
Shield
No Connection





Late TU Cam Sensor

The TU models have a Hall Effect cam sensor.




TU Cam Sensor Wiring
Sensor Pin
Function
Haltech Connection
1
12V+
12V+ Red in Home 4-core
2
Signal
Home + Yellow in Home 4-core
3
Signal Ground
Signal Ground Blue in Home 4-core



Ignition Coils and Igniters


Coil Pin
Colour
Function
1
Varies
To Igniter Module
2
Brown
Ground to Cylinder Head
3
Green
12V+

The ignition coils have 3x pins however they do not have an internal igniter. The igniter is internal to the OEM ECU, so an external igniter such as the Haltech HPI6 is recommended for this application.




Dwell Time








Throttle Position Sensor



OEM Wiring
Haltech Wiring
1
Signal Ground
2
Signal (Spare AVI)
3
5V+




MAP Sensor

These engines do not come with a MAP sensor.
Use the internal MAP sensor that comes with your ECU.  For higher boost levels an external MAP sensor should be used instead, connected to a spare AVI.









Variable Cam

TU Models

These models have a switched cam control that BMW calls VANOS (variable nockenwellen steuerung) that is simply turned on or off with the inlet cam only. When engaged will advance the inlet cam 25deg. This will use the Cam Control Switched function.  It will be off at idle, on at low RPM and open throttle, and turns off above ~4000 to 5000 rpm.








Idle Valve


3-pin BAC valve.   Middle pin is 12V+ and output pins will go to 2x spare outputs.







Coolant Temperature

M50B20 Coolant Temperature Sensor


Wiring is not polarity sensitive
Pin
Haltech Connection
1
Any Spare AVI*
2
Signal Ground
An AVI with a selectable Pullup should be used.  If not and external 1k pullup to 5V should be connected.








Air Temp

The M50 engine comes with an intake air temperature sensor.


Wiring is not polarity sensitive
Pin
Haltech Connection
1
Any Spare AVI*
2
Signal Ground
An AVI with a selectable Pullup should be used.  If not and external 1k pullup to 5V should be connected.










Knock Sensor

The M50 has 2x knock sensors.

Recommended Knock Sensor.  Haltech HT-011100










O2 Sensor

For correct operation a Haltech WB1 kit is highly recommended for this application, with the provided 4.9 sensors replacing the pre-cat sensor.  Sensors use a 22mm socket or spanner to remove and replace.











MAF Sensor

The M50 engine has a MAF. Although most Haltech installation will delete the MAF it can be used if the tuner prefers.


Wiring
Pin
Function
Haltech Wiring
1
Chassis Ground 
---
2
Signal Ground
Signal Ground (Black/White)
3
12V+ Switched
---
4
MAF Signal
Spare AVI











Injector Data


Flow

The injector flow rate is measured with the injectors held wide open at 100% duty.  For fuel systems with a fixed regulator pressure (often returnless systems) that is not referenced to manifold pressure the flow needs to be mapped over Manifold Pressure for accurate tuning.





Dead Time

When an injector is commanded to open for a certain amount of time, the dead time is the amount of time the injector is not actually open during this period.  It covers the time to energise the solenoid and begin to open and the time to close as well.  There are also transient periods during which the injector is opening and closing where fuel flow is not at full capacity so this lost peak flow period is also taken into account.  









OEM ECU Information

M50B20 ECU



M50B20TU use MS40.1








ECU Pinout




MS40.1 ECU Pinout








  

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