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The BMW M52 inline 6-cylinder engine was used in a variety of BMW models, including the E36 3 Series, the E39 5 Series Sedan, the Z3 and the E46 3 Series.

The M52 was an upgrade to the successful M50 engine. The M52 was produced in 2.0 (M52B20), 2.5 liter (M52B25) and 2.8 liter (M52B28) configurations. When the BMW E46 3 Series was launched in 1999, the M52TU engine was introduced in the E46 323i, E46 328i and the E39 528i models. The major changes in this Technical Update were the redesigned crankcase, modified pistons, Double VANOS for the camshaft drive, and Siemens MS42 DME system. Later, the E39 523i was introduced with the M52B25TU engine.

BMW took a large step in 1994 with the introduction of an aluminum block with the wear-resistant Nikasil coating on the cylinder bores. This reduced the engine's weight from around 190 kg (M50) to some 160 kg (M52). The camshafts were now fitted with counterbalancing masses, as was already the case on those of the eight-cylinder engine.

With the introduction of the M52 a new BMW power-output characteristic was introduced as well. The maximum power of 192 bhp previously achieved with the 2.5-liter engine was now reached with a 2.8 liter engine that delivered a significantly higher maximum torque. The new 2.5-liter engine was positioned between the 2.0-liter and 2.8-liter versions with its 170 bhp.

As a special version for four countries with high-sulfur gasoline, the M52 was supplied with a cast-iron cylinder block. The Nikasil cylinder coating would have had marginal reliability under those operating conditions.

In 1998 the VANOS system, which initially adjusted only the inlet camshaft was developed into the Double-VANOS system which now adjusted the timing of the exhaust camshaft as well. This opened the potential for further optimization of the engine's performance.

Double VANOS
Double-VANOS system

The inlet system was provided with two technical refinements in 1998. One was a flap valve in the inlet plenum chamber that cut off the inlet passages of the front three cylinders from the rear three. The differentiated intake system, known as DISA, optimized the engine's running under full load. The other refinement was a dedicated system of tubes of very small diameters through which the inlet air was drawn during idling or when running at low loads. The increased turbulence that this achieved improved the combustion process and thus reduced exhaust emissions.

In order to be able to offer a single cylinder block to all markets throughout the world, the aluminum block was given dry cast-iron liners.

source: Geschichte des Motors, Dr. Karlheinz Lange


Engine Codes  Engine Specifications
Item/Measurement M52B20 M52B20 M52B25 M52B25
Vehicle 320i 320i 523i 323i
Number of Cylinders 6 6 6 6
Layout in-line in-line in-line in-line
Installation 30° inclined right 30° inclined right 30° inclined right 30° inclined right
Coolant liquid liquid liquid liquid
Crankcase/Block Material aluminum aluminum aluminum aluminum
Crankshaft one-piece one-piece one-piece one-piece
Main Bearings 7 7 7 7
Weight (kg) 166 177 166 177
Valve Layout dohc dohc dohc dohc
Camshaft Drive simplex chain simplex chain simplex chain simplex chain
Camshaft Bearings 7 each 7 each 7 each 7 each
Valves per Cylinder 4 4 4 4
Cylinder Center Distance (mm) 91 91 91 91
Displacement (liters) 1.991 1.991 2.494 2.494
Bore/Stroke (mm) 80/66 80/66 84/75 84/75
Stroke/Bore Ratio 0.83 0.83 0.89 0.89
Piston Speed (ms) 13.0 13.0 13.8 13.8
Valve Timing (IO/IC) 4°btdc/44°abdc 6°atdc/54°abdc 4°btdc/44°abdc 6°atdc/54°abdc
(EO/EC) 39°bbdc/9°atdc 47°bbdc/17°atdc 39°bbdc/9°atdc 47°bbdc/17°atdc
At Valve Lift (mm) ER-ER ER-ER ER-ER ER-ER
Valve Lift I/E (mm) 9.0/9.0 9.0/9.0 9.0/9.0 9.0/9.0
Connecting Rod Length (mm) 145 145 140 140
Connecting Rod Ratio r/l 0.23 0.23 0.27 0.27
Compression Ratio 11.0:1 11.0:1 10.5:1 10.5:1
Fuel Norm-Sup Plus LF Norm-Sup Plus LF Norm-Sup Plus LF Norm-Sup Plus LF
Power Output (bhp@rpm) 150/5900 150/5900 170/5500 170/5500
Power per Liter (bhp/liter) 75.34 75.34 68.16 68.16
Power/Weight Ratio (kg/bhp) 1.11 1.18 0.98 1.04
Torque (mkg@rpm) 19.4/4200 19.4/3500 23/3950 23/3500
Torque per Liter (mkg/liter) 9.73 9.73 10.01 10.01
Mixture Preparation fuel injection fuel injection fuel injection fuel injection
 Maker Siemens Siemens Siemens Siemens
 Designation DME MS41.0 DME MS42.0 DME MS41.0 DME MS42.0
Ignition integrated integrated integrated integrated
Ignition Advance map map map map
Generator 12 V/1120 W 12 V/1120 W 12 V/1260 W 12 V/1260 W
Supercharging - - - -
Miscellaneous VANOS, KD Double VANOS, KD VANOS, KD Double VANOS, KD
Year of Introduction 1994 1998 1995 1998

source: Geschichte des Motors, Dr. Karlheinz Lange


Engine Codes  Engine Specifications, contd.
Item/Measurement M52B28 M52B28    
Vehicle 328i 328i    
Number of Cylinders 6 6    
Layout in-line in-line    
Installation 30° inclined right 30° inclined right    
Coolant liquid liquid    
Crankcase/Block Material aluminum aluminum    
Crankshaft one-piece one-piece    
Main Bearings 7 7    
Weight (kg) 170 180    
Valve Layout dohc dohc    
Camshaft Drive simplex chain simplex chain    
Camshaft Bearings 7 each 7 each    
Valves per Cylinder 4 4    
Cylinder Center Distance (mm) 91 91    
Displacement (liters) 2.793 2.793    
Bore/Stroke (mm) 84/84 84/84    
Stroke/Bore Ratio 1.0 1.0    
Piston Speed (ms) 14.8 15.4    
Valve Timing (IO/IC) 1°atdc/49°abdc 6°atdc/54°abdc    
(EO/EC) 39°bbdc/9°atdc 47°bbdc/17°atdc    
At Valve Lift (mm) ER-ER ER-ER    
Valve Lift I/E (mm) 9.0/9.0 9.0/9.0    
Connecting Rod Length (mm) 135 135    
Connecting Rod Ratio r/l 0.31 0.31    
Compression Ratio 10.2:1 10.2:1    
Fuel Norm-Sup Plus LF Norm-Sup Plus LF    
Power Output (bhp@rpm) 193/5500 193/5500    
Power per Liter (bhp/liter) 69.10 69.10    
Power/Weight Ratio (kg/bhp) 0.88 0.93    
Torque (mkg@rpm) 28.5/3950 28.5/3500    
Torque per Liter (mkg/liter) 10.22 10.22    
Mixture Preparation fuel injection fuel injection    
 Maker Siemens Siemens    
 Designation DME MS41.0 DME MS42.0    
Ignition integrated integrated    
Ignition Advance map map    
Generator 12 V/1260 W 12 V/1260 W    
Supercharging - -    
Miscellaneous VANOS, KD Double VANOS, KD    
Year of Introduction 1994 1998    

source: Geschichte des Motors, Dr. Karlheinz Lange


links

Links

Performance Parts for your BMW M52 engine.

Repair Tips to keep your BMW M52 in top shape.

BMW engine and model codes.

Engine Technology:

Engine Cleaning. Be careful with your BMW M52 engine.

Wallpaper of BMW engines. More...

More engine links.

Do not buy an M52 320/323/328 with an alloy block made before 3/98 unless it's had a new engine under warranty or you get a compression check done. Sulfur in fuel causes premature bore wear which shows as a bad idle and lack of power. Only solution is a new block. - John G. Burns

John G. Burns E36 page has some tips for M52 engines.

Nikasil coating information.



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