M52 Engine
Information on the BMW M52 Engine
General Information
| Cylinders | 6 |
| Displacement | B20 1991cc (121ci) B24 2394cc (146ci) B25 2494cc (152ci) B28 2793cc (170ci) |
| Firing Order | 1,5,3,6,2,4 |
Model Variants
There are a number of variants of the M52 engine. TU models refer to "Technical Update" and added VANOS to the exhaust cams, Drive-By-Wire throttle, and a variable length intake system.
M52B20
11.0:1 comp. 6500rpm limit for all models
M52TUB20
1998-on, Dual VANOS, DBW, Variable Intake Length
M52TUB24
Thailand Only
M52B25
10.5:1 comp
M52TU25
1998-2000, Dual VANOS, DBW, Variable Intake Length
M52B28
10.2:1 comp
M52TUB28
1998-on Dual VANOS, DBW, Variable Intake Length
Common Models
| Engine Type | Common Vehicles |
| M52B20 | |
| M52TUB20 | |
| M52B25 | |
| M52TUB25 | |
M52B28 |
|
M52TUB28 |
Sensor Information
Crank/Cam Sensor
This engines uses a Crank Position Sensor and 1x Cam Position Sensor for normal models, or 2x cam position sensors for TU models.
Crank Sensor
A Hall Effect crank position sensor is used and is located on the front of the engine with the 60-2 trigger being part of the crank pulley.
Wiring
| Sensor Pin | Function | Haltech Connection |
1 | 5V+ | 5V+ Orange |
2 | Signal | Trigger + Yellow in Trigger 4-core |
3 | Signal Ground | Signal Ground Blue in Trigger 4-core |
Cam Sensor Non-TU Models
Early engine models use a unique cam sensor design. The OEM ECU sends the sensor a frequency signal, and the pattern is altered if a cam tooth is present under the sensor. This type of "frequency sensor" is not supported by Haltech or any other aftermarket ECU. A single "half-moon" tooth is used
The Yellow pattern is the crank sensor 60-2 signal. The Blue pattern shows the frequency signal. When a tooth is present a higher frequency is produced.
Image from VEMS.
To support these models the cam position sensor should be replaced with a conventional Hall Effect type sensor. Most people replace sensor with one from the M50 engine. Pinout is the same as for the Siemens sensor.
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 |
Cam Sensor TU Models
TU Model engines are reported to use normal Hall Effect sensors. These are supported by Haltech Elite ECUs.
Wiring is the same as for non TU models.
Trigger Configuration
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
DBW Throttle System
Models with the Technical Update will have a DBW Throttle. Other models use a conventional cable throttle.
DBW Throttle Wiring
Position Sensors
| Pin | Description | Haltech Connection |
| 1 | 5V+ | 5V+ |
| 2 | TPS2 | AVI3 |
| 4 | TPS1 | AVI2 |
| 5 | Signal Ground | Signal Ground |
Drive Motor
| Pin | Haltech Connection |
| 3 | DBW1 |
| 6 | DBW2 |
DBW Accelerator Pedal Position Sensors Connection
| Pin | Description | Haltech Connection |
| 1 | Signal Ground | Signal Ground |
| 2 | APP2 | AVI5 |
| 3 | Signal Ground | Signal Ground |
| 4 | 5V+ | 5V+ |
| 5 | APP1 | AVI4 |
| 6 | 5V+ | 5V+ |
Throttle Position Sensor (Cable Throttle Models)
| 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 Cams
Non TU models
These models have a switched cam control that is simply turned on or off with the inlet cam only. 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 ~4200rpm.
TU Models
These models have continuously variable cams on the inlet and exhaust cams. This will use the Cam Control function.
Idle Valve
3-pin BAC valve. Middle pin is 12V+ and output pins will go to 2x spare outputs.
Coolant Temperature
M52B28 Coolant Temperature Sensor
M52TUB28 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.
Calibration: Use "Temperature - xxxxxxx.cal"
Created for Haltech ECUs using a 1k pullup to 5V
Air Temp
An air temperature sensor is incorporated in the MAF Sensor. If the MAF is deleted then an external Air Temperature Sensor needs to be installed in the intake, preferably in the plenum near to where the MAP sensor connects.
Haltech 1/8" NPT Air Temp Sensor
Wiring is not polarity sensitive.
Calibration: Use "Temperature - GM Air Sensor.cal"
Created for Haltech ECUs using a 1k pullup to 5V
Knock Sensor
Recommended Knock Sensor. Haltech HT-011100
O2 Sensor
Adding a Haltech Wideband Kit (highly recommended)
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.
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
Siemens ECUs are used by BMW for these engines.
Non TU use MS41.0
TU use MS42
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