BMW N42B20 Engine

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

N42B20 Specs

Manufacturer BMW Plant Hams Hall
Also called BMW N42
Production 2001-2004
Cylinder block alloy Aluminum
Configuration Straight-4
Valvetrain DOHC
4 valves per cylinder
Piston stroke, mm (inch) 90 (3.54)
Cylinder bore, mm (inch) 84 (3.3)
Compression ratio 10
Displacement 1995 cc (121.7 cu in)
Power output 105 kW (143 HP) at 6,000 rpm
Torque output 200 Nm (148 lb·ft) at 3,750 rpm
Redline 6,500 rpm
HP per liter 71.7
Fuel type Gasoline
Fuel system Bosch ME 9.2
Weight, kg (lbs) 120 (265)
Fuel consumption, L/100 km (mpg)

for E46 318i
10.0 (23.5)
5.5 (42.8)

7.2 (32.7)
Turbocharger Naturally aspirated
Oil consumption , L/1000 km
(qt. per miles)
up to 0.7
(1 qt. per 850 miles)
Recommended engine oil 5W-30
Engine oil capacity, L (qt.) 4.25 (4.5)
Oil change interval, km (miles) 7,000-10,000
Normal engine operating temperature, °C (F)
Engine lifespan, km (miles)
-Official information

250+ (155)
Tuning, HP
-Max HP
-No life span loss


The engine is installed in BMW 318i E46

BMW N42B20 engine reliability, problems and repair

BMW N42B20 is a straight 4-cylinder engine that was produced in 2001 to replace M43B18, M43TU and M44B19 older versions. Heavy iron-cast cylinder block was replaced by lighter aluminum alternative with iron-cast sleeves. N42B20 uses new long crankshaft with 90 mm stroke as well as new pistons and connecting rods. Balance shafts are the same as in M43TU. They were modified a bit in order to suit new block of cylinders.
SOHC 8V cylinder head was replaced by new DOHC 16V. At the same time cylinder head was additionally equipped by Double-Vanos variable valve timing system along with variable valve lift system Valvetronic. Hydraulic lifters are still used for this series of BMW engines. Diameter of inlet and outlet valves is 32 and 29 mm respectively. Stock camshaft specs are as follow: duration 250/258 deg, lift 9.7/9.7 mm.
N42B20 has variable-length intake manifold DISA which makes it possible to optimize characteristics at high and low rpm.
New engine is equipped by Bosch ME 9.2 motor control unit.
This engine was used in BMW 18i models.
Younger N42B18 engine version was developed on base of this engine.
N42B20 was replaced by new types of engines N45B20S and N46B20 in 2004. Third successor of the motor appeared in 2007. It was N43B20.

BMW N42B20 disadvantages and problems

1. Overheating. This problem mainly results from polluted radiator. It requires regular cleaning. Another problem is broken thermostat which needs to be replaced every 60,000 miles (100,000 km) of mileage. Valve stem seals go out of order resulting in higher motor oil consumption. Also pay attention to operation of cooling system.
2. N42 noise. Replacement of timing chain tensioner can be efficient solution to this problem. It should be changed every 60,000 miles (100,000 km) of mileage. At the same time N42 has not very reliable timing chain. It starts making noise and stretches every 60,000 miles (100,000 km) of mileage.
Moreover BREMI ignition coils may get out of order while replacing spark plugs. If you have faced such problem you are recommended to change them on EPA ignition coils.
N42 establishes rather high requirements to motor oil. That is why you are supposed to use motor oil that is recommended by auto producer. If you use oil of lower quality it can lead to rebuild, Vanos replacement and many more.
Summing up N42 is rather technological and economic engine. At the same time it can be rather demanding. The level of its reliability is the same as in M40-M43 series and it calls for regular examination and control as well as high quality maintenance.

BMW N42B20 engine tuning

N42B20 Chip tuning

N42 engines are not the best choice for tuning. You may face difficulties in finding necessary dimensions and performance parts on the market. That is why you will hardly be able to implement serious upgrading project. The only way to increase the level of HP is to proceed with chip tuning. You need to buy cold air intake and cat back performance exhaust system. Don’t forget to complete engine management tuning to make everything work properly. Such modifications will make it possible to increase power rate up to 160 HP.
If you still require more power the best way is to sell your BMW 318i and buy BMW M3 E46.