The BMW M50B20 engine, together with its modernized version M50B20TU, was produced at the Munich and Steyr plants between 1990 and 1996. It is one of the company’s most famous engines, which provided high performance and reliability in various BMW car models.
Characteristics
The M50B20 is an inline six-cylinder engine with a cast iron cylinder block and an injector-based power system. The cylinder diameter is 80 mm and the piston stroke is 66 mm. The engine has a compression ratio of 10.5, which is increased to 11 in the TU (Technical Update) version. The engine displacement is 1991 cc.
Power output reaches 150 hp at 6000 rpm (150 hp at 5900 rpm for the TU version) and maximum torque is 190 Nm at 4700 rpm (190 Nm at 4200 rpm for the TU version). The engine weighs 194 kg, which provides a good balance between power and weight.
Economy and performance
Fuel consumption for the BMW E36 320i is 11.2 liters per 100 km in the city, 6.7 liters on the highway and 8.6 liters in the mixed cycle. Oil consumption does not exceed 1000 grams per 1000 kilometers. It is recommended to fill the engine with oil with viscosity 5W-30, 5W-40, 10W-40 or 15W-40 with a volume of 5.75 liters. Oil change should be carried out every 7000-10000 km.
The operating temperature of the engine is about 90 degrees Celsius. The factory warranty on the engine resource is not specified, but in practice it is able to run more than 400 thousand kilometers.
The M50B20 engine has a significant potential for tuning. The maximum power that can be achieved with this engine is more than 300 hp, but without loss of resource it is possible to get 190-200 hp.
Application
The M50B20 engine was installed in the BMW 320i E36 and BMW 520i E34 models. These cars were in great demand due to the high level of reliability and performance of the engine, which provided excellent performance on the road and driving comfort.
Reliability and repair of the BMW M50B20 engine
The smallest inline six of the BMW M50 series (the family also included the M50B24, M50B25, S50B30, S50B32) was released in 1990 as a replacement for the outdated M20B20. Here is a new cast iron cylinder block with oil injectors, the intercylinder distance remained the same – 91 mm, but the height has changed to 210 mm. Inside this block is a new crankshaft with a stroke of 66 mm, lightweight forged connecting rods 135 mm, new pistons with compression height of 42.8 mm. So we get 2 liters on 6 cylinders.
The main innovation here is the use of a new cylinder head with 4 valves per cylinder and two camshafts, as well as with hydrocompensators. It uses camshafts with 240/228 phase and 9.7/8.8 mm lift. The intake valves are 30mm in diameter, the exhaust valves are 27mm and the stem diameter is 7mm. Double valve springs are used here.
Among other things, in the M50B20 belt drive timing gave way to a more reliable chain drive, the service life of which is more than 250 thousand kilometers.
The M50 has an intake manifold made of plastic, more perfect contruktion, instead of the trampler used individual ignition coils, electronic ignition system, injectors M50 – 154 cc.
Control system – Bosch Motronic 3.1/Siemens MS40.0.
Update
In 1992, the M50 engines received an upgrade, the purpose of which was to reduce fuel consumption and improve environmental friendliness by reducing friction. These engines are called M50B20TU or simply vanosny M50. They were equipped with a phase shifter on the intake shaft (Vanos), and also received new lightweight connecting rods (length 145 mm), much lighter pistons (-100 grams), and the compression height of the piston decreased to 31.64 mm. Lightweight valves were put here, with single less stiff valve springs. The valve stem size is now 6mm.
The engine management system was changed to Siemens MS 40.1.
All these motors were used on BMW cars with the index 20i.
In 1994, the low-volume M50 was replaced by a new more advanced M52B20, with the same displacement.
Modifications of the BMW M50B20 engine
- M50B20 (1990 – 1992) – the basic variation of the engine. Compression ratio 10.5, power 150 hp at 6000 rpm, torque 190 Nm at 4700 rpm.
- M50B20TU (1992 – 1996) – added Vanos system (phase shifter on the inlet), replaced the CMP, used camshafts with phase 228/228, lift 9/9 mm, compression ratio increased to 11. Power 150 hp at 5900 rpm, torque 190 Nm at 4200 rpm.
Problems and shortcomings of BMW M50B20 engines
Typical problems of M50B25 engines include:
Overheating
These engines are hard to tolerate temperature violations, so be sure to check the condition of the radiator, pump and thermostat, make sure there are no blockages in the engine cooling system, check all hoses and pipes for leaks. It is recommended to change the oil every 7-10 thousand km, and it is necessary to choose it strictly according to the catalog, recommended by the manufacturer.
Thrashing
This symptom of unstable engine operation is most often explained by the failure of the ignition coil. It is also worth checking the spark plugs and injector injectors.
Swimming revs
The cause may be a faulty idle valve: it needs to be cleaned. If the problem can not be eliminated in this way, you should check the throttle position sensor (DPDZ), as well as the engine temperature sensor and lambda probe. Throttle valve cleaning is a mandatory engine maintenance procedure.
Vanos system
The problem with “vanos” makes itself known by the engine rumbling, a drop in its power, floating revolutions. Often the problem can be solved by buying a repair kit, but if the “vanos” fails, buying them for replacement will hurt the wallet.
Maslozhor
Because of its venerable age, and also as a result of aggressive driving, M50 engines are characterized by an increased oil appetite. Oil spoilage reaches up to 1 liter per 1000 km of mileage, and even overhaul does not eliminate the problem. Oil leaks through the gaskets of the valve cover and sump, sometimes – right through the dipstick.
Other problems
Often owners complain about a cracked expansion tank, as a result of which antifreeze leaks from the cooling system. It is worth to keep an eye on the camshaft and crankshaft sensors (DPKV), coolant temperature.
Tuning the BMW M50B20 engine
M50B20 Stroker
It’s no secret that the 2-liter engine is not striking acceleration and many owners of M50B20 do not mind to increase the power, without losing much in reliability. The easiest way would be to buy an M50B25 engine for Swap. If we consider the options of modifying the native engine, the easiest option to raise the output is to increase the working volume to 2.6 liters, and with standard BMW parts.
For this step we will need to buy a crankshaft and air flow sensor from M52B28, connecting rods are stock, pistons are bought from M50TUB20. Injectors, throttle plate, fuel pressure regulator and tuned ECU is taken from M50B25. After these transformations we get a compression ratio of ~12 and power of about 200 hp, pour 98 gasoline and drive without problems, or put a thick cylinder-head gasket and pour 95, as a variant you can remove from the bottom of the piston 0.3 mm and do without a standard gasket.
If the motor with vanos, then put the crankshaft and connecting rods from M52B28, injectors from M50B25.
To our new motor M50B26 opened to the full, you need to buy an intake manifold and throttle from M50B25, make porting head, combine the channels and install the exhaust equal-length manifold with full exhaust from M50B25 or sports. These modifications will allow the engine to breathe freely and the maximum power will increase significantly. The dynamic characteristics of the car with the M50B26 engine and all the above tuning will be significantly higher than the usual one
M50B25
The next step could be the M50B20 Stroker 3.0. To get 3 liters of displacement, we need to bore the cylinders to 84 mm and buy pistons with rings, connecting rods with liners and crankshaft from BMW M54B30. The cylinder block is bored by 1 mm. To this we buy the cylinder head, main liners from M50B25, timing chain with tensioner and caliper, as well as all gaskets and injectors 250 cc. After assembling all of this on an M50B20 block, we will have a complete M50B30 Stroker.
To get maximum power without a turbo on the M50B30 Stroker, we need to throw out the stock camshafts and buy Schrick 264/256 (or other similar), 6 throttle intake, injectors and MAP sensor from S50B32, exhaust from BMW S38. After tuning we will get about 250-270hp and sometimes more.
M50B20 Turbo
The easiest way to turbocharge an M50 is to buy a Garrett GT30 based turbo kit with turbo manifold, westgate, block-off, MAP sensor, wideband lambda probe, boost controller, full intake, intercooler, 440 cc injectors and full exhaust. To make it all go you need to tune the brain. The output will be about 300 hp on stock pistons.
For more power you need to replace the turbo on Garrett GT35, injectors at 500 cc, stock pistons change to CP Pistons with a compression ratio of 8.5, Eagle connecting rods, APR bolts, metal cylinder head gasket, tuned and get 400++ hp.
ENGINE RATING: 5-