BMW N45 Engine Most Common Problems And Reliability

The BMW N45 is an inline four-cylinder engine from a Bavarian company. It is an update to the N40.  This naturally aspirated engine was used in the BMW E46 generation until it appeared under the hood of the BMW 116i.

And the BMW 316ci and 316ti models were sold in countries where large engine sizes were heavily taxed. Therefore, BMW decided that cars with a 1.8-liter N42 engine would not be popular.

The N45, like the N42 engine, uses ME9 control units, has 16 valves and a dual VANOS system. The differences with the N42 are mainly in the absence of Valvetronic. The N45N version used the ME1745 electronic control units.

The 2 liter version N45B20S occupies a special position. It was installed in a generation in the BMW 320si of the E90 generation.

This model was a limited edition car (2600 units) sold since 2006 as a homologation model for the World Touring Car Championship (WTCC).

The engine had distinctive features – the cylinder liners were made of aluminum alloy and installed inside the cylinder bores.

In the case of the normal versions of the N45/N46 engine, they are usually made of gray cast iron and are cast inside the cylinder block.

Other features are reinforced connecting rods and oil pan (aluminum base and gray cast iron inserts. The compression ratio has been increased from 10.5 to 11.

Cylinder head castings were produced in the Formula 1 workshop located at the BMW plant in Landshut, Germany .

Due to the high temperature stress during sporting events, the coolant passages in the engine have been specially designed to be large.

The six-cylinder versions used water cooling. The rocker arms of the N45B20S engine had a special coating, and the spark plugs were controlled by individual ignition coils.

The engine was largely hand-built at the BMW plant in Hams Hall , UK.

Read Also: 16+ The Most Reliable BMW Engine Ever Made

Characteristics of the BMW N45 engine

 Technical specifications N45B16 N45B20
 Working volume, cm³ 1596 1997
 Cylinder diameter / piston stroke, mm 84/72 85/88
 Power, hp (kW)/rpm 115 (85)/6000 (6100*) 173 (127)/7000
 Torque, Nm/rpm 150/4300 (3900*) 200/4250
 Liter power, kW/l 53.3 63.6
 Compression ratio, :1 10.2 11.0
 The engine control unit ME17.4.5/ME9* ME9.2
 Engine weight, ∼ kg 80 95
* – before the update in 2007;

1. BMW N45B16 engine

N45B16O1 engine was produced from March 2004 to September 2007 and was created on the basis of the 1.6-liter M43, only instead of 2, it is equipped with 4 valves per cylinder.

In 2007, an updated version of the N45N engine (N45B16O2) was equipped with a new engine management system – ME17.4.5 and was produced until 2011.

The 1.6-liter version was installed on:

  • BMW E81 116i
  • BMW E87 116i
  • BMW E46 316Ci Coupe
  • BMW E46 316ti Compact
  • BMW E90 316i / BMW E91 316i

2. BMW N45B20S engine

The 2-liter N45B20O0 engine was installed from January 2006 to June 2007 on the limited production model BMW E90 320si and was produced mainly by hand.

This power unit has a number of design features, unlike the 2-liter N42:

  • liners were made of aluminum alloy;
  • reinforced connecting rods and crankcase;
  • the compression ratio has been increased from 10.5 to 11;
  • the engine block is made of gray cast iron;
  • the coolant channels from the cylinder head were enlarged and the water cooler was taken from the 6-cylinder power unit;

BMW N45 Engine problems

Some basic malfunctions during operation of the N45 Engine:

  1. Detonation combustion of fuel: the reason problem is the use of low-quality fuel and oil:
    Recommendation: it is necessary to correct the ignition parameters, but this will lead to a loss of engine efficiency at high speeds (this problem can be corrected thanks to the knock control system of which the 1.6-liter engine is equipped);
  2. Engine knock: the reason problem is in the timing chain tensioner, which are perhaps a common problem in this engine (estimated service life is about 100,000 km);
  3. Idle vibrations: the reason problem is mainly in Vanos:
    Recommendation: cleaning the Vanos system;

The BMW N45 engine was replaced by the N13 engine .

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