BMW N45B20S Engine Specs, Problems And Reliability

The 2 liter N45B20S engine was produced in a limited edition and was installed only on the BMW E90 320si. The engine was developed on the basis of the N42B20, compared to the previous N45B20S engine, it has a cylinder diameter increased by 1 mm (it was 84 mm, it became 85 mm), as well as a reduced piston stroke by 2 mm (it was 90 mm, it became 88 mm) due to another crankshaft.

In addition, reinforced connecting rods are used on the motor and the compression ratio is increased to 11. Instead of cast iron liners, aluminum liners are used on this motor.

Here is another cylinder head with other camshafts and valves, and a carbon fiber cylinder head cover. On the N45B20S, unlike the N42B20, there is no Valvetronic valve lift system. Timing chain drive, there are hydraulic lifters.

There is a Double Vanos variable valve timing system.

A more common N45B16 engine was produced, which has a smaller volume and less power. Together with the N45B20S, the N43B20 and N46B20 were produced. In 2011, the production of another motor N13B16 began.

Problems and malfunctions of the N45B20S engine

  1. You need to carefully choose a gas station, this engine is demanding on fuel quality. Otherwise, detonation may occur, which can seriously affect the future life of the motor.
  2. Engine knock often comes from a worn chain tensioner, and the chain itself is not famous for its reliability. The chain can stretch for about 100 thousand kilometers.
  3. Clean Vanos can help eliminate motor vibrations.
  4. Engine oil consumption may increase due to worn valve stem seals.

In addition, the engine is prone to detonation and accordingly, to the quality of fuel, as well as oil. It is not recommended to joke with oil, you only need to pour what is recommended by BMW, otherwise there is a chance to get big problems up to a major overhaul.

Reliability of the N45B20S engine

  1. Changer N42B20 , which was born in a limited edition in 2006 specifically for the BMW 320si E90. To some extent, the N45B20S engine is the heir to the old M44 , also used on si models.
  2. Compared to the simple N42, the new engine received a different crankshaft with a piston stroke reduced by 2 mm (was 90 mm), along with this, the cylinder diameter increased to 85 mm (was 84 mm).
  3. Cast iron liners were replaced with aluminum alloy liners, the connecting rods were replaced with reinforced ones, the compression ratio was increased to 11.
  4. A new cylinder head was used with larger valves, with different camshafts and without using the Valvetronic valve lift system. A striking difference from all other four-cylinder N-engines is the carbon fiber cylinder head cover.
  5. In addition to the 2-liter engine, the N45 series produced a smaller displacement power plant N45B16 . Together with the N45, other four-cylinder successors of the N42 were also produced – N43B20 and N46B20 .
  6. The engine was replaced in 2011 in the form of a turbocharged four N13B16, with a working volume of 1.6 liters.

BMW N42B20 Specs

ProductionBMW Plant Hams Hall
Engine brandN45
Release years2006-2007
Block materialAluminum
Supply systemInjector
Type ofIn-line
Number of cylindersFour
Valves per cylinderFour
Piston stroke, mm88
Cylinder diameter, mm85
Compression ratio11
Engine volume, cc1997
Engine power, hp / rpm177/7000
Torque, Nm/rpm210/4250
Environmental regulationsEuro 4-5
Engine weight, kg
Fuel consumption, l / 100 km (for 320si E90)

– City

– Highway

– Mixed


Oil consumption, g/1000 kmup to 700
Engine oil5W-30 / 5W-40
How much oil is in the engine, l4.5
Oil change is carried out, km10000
Operating temperature of the engine, hail.
Engine resource, thousand km

– according to the plant

– in practice


BMW N42B20 Tuning

Unlike N45B16 tuning N45B20S makes sense. On sale there are more evil camshafts for example Schrick 268/260, you can find even more evil.

Then you need to purchase a cold intake, install a sports exhaust and do chip tuning. After all this, the engine power will increase to 200 hp. If you wish, you can still port the cylinder head, which will add a little more power.


In 2006, the N45 engine received a new modification – N45B20S with a displacement of 1997 cubic meters. see The updated in-line 4-cylinder engine differs from its predecessor in terms of power – 126 kW (173 l / s).

In addition to improving the technical characteristics, the main technological improvement of the engine has undoubtedly been the use of the innovative Valvetronic system, which significantly increases the efficiency of the entire engine as a whole.

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