BMW M50B20 / M50TUB20 Engine

  1. Specifications
  2. Overview, problems
  3. Performance tuning

M50B20 / M50TUB20 Specs

Manufacturer  Munich Plant
Also called BMW M50
Production 1990-1996
Cylinder block alloy Cast iron
Configuration Straight-6
Valvetrain DOHC
4 valves per cylinder
Piston stroke, mm (inch) 66 (2.6)
Cylinder bore, mm (inch) 80 (3.15)
Compression ratio 10.5
11 (TU)
Displacement 1991 cc (121.5 cu in)
Power output 110 kW (150 HP) at 6,000 rpm
110 kW (150 HP) at 5,900 rpm (TU)
Torque output 190 Nm (140 lb·ft) at 4,700 rpm
190 Nm (140 lb·ft) at 4,200 rpm (TU)
Redline 6,500 rpm
HP per liter 75.3
Fuel type Gasoline
ECU Bosch Motronic 3.1
Siemens MS40.0
Siemens MS40.1 (TU)
Weight, kg (lbs)
Fuel consumption, L/100 km (mpg)

for E36 320i
11.2 (21)
6.7 (35.1)

8.6 (27.4)
Turbocharger   Naturally aspirated
Oil consumption , L/1000 km
(qt. per miles)
up to 1.0
(1 qt. per 750 miles)
Recommended engine oil 5W-30
Engine oil capacity, L (qt.) 5.75 (6.0)
Oil change interval, km (miles)  7,000-10,000
Normal engine operating temperature, °C (F) ~90 (194)
Engine lifespan, km (miles)
-Official information

400+ (250+)
Tuning, HP
-Max HP
-No life span loss


The engine is installed in BMW 320i E36
BMW 520i E34

BMW M50B20 engine reliability, problems and repair

BMW M50 series is equipped with the smallest straight 6-cylinder engine that was firstly introduced in 1990 and replaced the BMW M20B20. The series also includes M50B24, M50B25, S50B30 and S50B32. The main difference between M50B20 and M50B25 is in their capacity. B20 is a 2.0-liter engine while B25 is 2.5-liter motor. It is equal to series of engines which include M50B24 – 2.4 L, S50B30 – 3.0 L, S50B32 – 3.2 L.
At the same time new motor also had several innovations including new cylinder head, 24 valves and 2 camshafts. In addition new motor was equipped by hydraulic lifters. Specifications of M50B20 camshafts are as follows: duration – 240/228 deg, lift – 9.7/8.8 mm. Diameter of inlet and exhaust valves is 30 mm and 27 mm respectively.

Other differences include individual ignition coils, new pistons, new 135 mm lightweight connecting rods. The size of M50B20 injectors is 154 cc.

At the same time M50B20 timing belt was replaced by timing chain with higher level of reliability and duration which is more than 150,000 miles (250,000 km) of mileage.

In 1992 these engines were also equipped with phase shifters. They were installed in Vanos inlet valve. At the same time the name of engines has also been changed into M50TUB20. The length of connection rods was 145 mm.
The given engine was mainly used in BMW models with 20i index.

In 1994 2-liter M50B20 engine was replaced by new upgraded M52B20 with the same production displacement.

BMW M50B20 engine modifications and differences

1. M50B20 (1990 – 1992) is a base modification of engine. Specifications are as follows: compression ratio – 10.5, power – 150 HP at 6,000 rpm, 190 Nm of torque at 4,700 rpm.

2. M50B20TU (1992 – 1996) was additionally equipped by Vanos phase shifter placed on the inlet valve with duration and lift specs 228/228 deg and 9/9 mm respectively. Specifications are as follows: compression ratio – 11, power – 150 HP at 5,900 rpm, 190 Nm of torque at 4,200 rpm.

BMW M50B20 engine problems and drawbacks

Speaking about possible malfunctions M50B20 engine is equal to its elder brother 2.5-liter M50B25. HERE you will be provided with detailed information on possible problems.

BMW M50B20 engine tuning

M50B20 Stroker. ITB

It is commonly known that 2-liter engine can hardly impress someone with its power. That is why the majority of M50B20 owner are looking for any possibility to add additional HP without losing in reliability and quality. The easiest way is to make Swap after purchasing M50B25 engine. If we speak of increasing HP of native motor, the only way is to increase its capacity up to 2.6 liters. Such project can be implemented using standard BMW spare parts and components. Those who want to take the advantage of such upgrade will need crankshaft as well as oxygen sensor which can be found in M52B28 engine. In addition you will also need stock connecting rods, M50TUB20 pistons, injectors, throttle body, fuel pressure regulator and tuned by M50B25 ECU. After such upgrade compression ratio will be increased up to 12 while HP will be about 200. If you need lower compression ratio you will need to install thick cylinder head gasket or take of -.3 mm from the bottom of the piston and use standard stock gasket.

If you are tuning M50B20 Vanos engine, you are supposed to install M52B28 crankshaft and connecting rods as well as M50B25 injectors.

If you are eager to reveal the whole potential of your M50B26 engine, you need to buy M50B25 intake manifold and throttle body. Then you need to make head porting and install exhaust headers with M50B25 full exhaust system. Sports exhaust system will also be a good choice for this purpose. Such modifications and improvements will reveal the whole potential of your engine and increase its HP rate. At the same time you will also benefit from better dynamic specifications of M50B26 engine. They will be much higher in comparison with standard modification of M50B25.

M50B20 Stroker 3.0 can be the following stage of the upgrade. If you want to obtain 3-liter engine, you need to bore cylinders up to 84 mm (Max bore) and buy new pistons with rings, connecting rods and crankshaft (All from the M54B30). Block of cylinders should be milled by 1 mm. At the same time you will also need new cylinder head and radical loose from M50B25. Don’t forget about timing chain equipped by tensioner and damper as well as all necessary gaskets and 250 cc injectors. When the assembly of new engine based on M50B20 is completed, you will get M50B30 Stroker.

If you want to make your M50B30 Stroker as powerful as possible without turbocharger, you should replace your stock camshafts with Schrick 264/256 deg camshafts or something equal to them. You will also need individual throttle bodies, injectors, exhaust system and MAP sensor which can be found in BMW S38. After tuning is over you will have engine with 250-270 HP or even more.

M50B20 Turbo

The best way to turn M50 engine into turbocharged motor is to buy turbo kit: Garrett GT30 turbocharger with blow-off, wastegate, intercooler, exhaust manifold, boost controller, downpipe, full exhaust system, MAP sensor, broadband lambda sensor, 440 cc injectors, intake manifold, throttle body, fuel regulator and intake pipe with filter. If you want to make it move, you need to tune it (ECU Megasquirt). When the upgrade is over you will get engine with 300 HP on stock piston.

If you need even more power, you should install Garrett GT35 turbocharge along with 500 cc injectors, CP Pistons with 8.5 CR, Eagle connecting rods, ARP bolts, metal cylinder head gasket. When the tuning is completed, you will have an opportunity to take the advantage of 400++ HP engine. If you do everything right, your auto equipped by turbocharged M50B20 will be able to speed up to 60 mph (0-100 kmh) in 5 seconds which is not bad a t all.