BMW N43B20

BMW N43B20The BMW N43B20 is a 2.0 liters (1,995 cc, 121.7 cu·in) straight-four, four-stroke cycle natural aspirated gasoline engine from the BMW N43-family. The engine was manufactured from 2007 to 2011 on the BMW Plant Hams Hall (Coleshill, Birmingham, United Kingdom).

The N43B20 engine features an aluminum cylinder block and aluminum head with a dual overhead camshaft (DOHC) and four valves per cylinder (16 in total). The cylinder bore is 84.0 mm (3.31 in) and the piston stroke is 90.0 mm (3.54 in). Compression ratio rating is 12.0:1.

This engine used a direct injection fuel system and the Siemens MSD 81.2 engine management system, dual VANOS (Variable Valve Timing System from BMW) for both inlet and exhaust camshafts, fully electronic throttle without mechanical backup. Redline is 5,000 rpm.

The N43B20 had three variants:

  • N43B20K0 – 122 PS (90 KW; 121 HP) at 6,000 rpm of horsepower and 185 Nm (18.9 kg·m; 136.5 ft·lb) at 3,000 rpm of torque. This engine was used on the BMW 116i (E81/E87).
  • N43B20U0 – 143 PS (105 KW; 141 HP) at 6,000 rpm of horsepower and 190 Nm (19.4 kg·m; 140.2 ft·lb) at 4,250 rpm of torque. This version was used on the BMW 118i (E81/E87/E88) and BMW 318i (E90/E91/E92/E93).
  • N43B20O0 – 170 PS (125 KW; 168 HP) at 6,700 rpm of horsepower and 210 Nm (21.4 kg·m; 155.0 ft·lb) at 4,250 rpm of torque. This version was used on the BMW 120i (E81/E82/E87/E88), BMW 320i (E90/E91/E92/E93) and BMW 520i (E60/E61).

The breakdown of the engine code is as follows:

  • N43 – Engine Family
  • B – Gasoline
  • 20 – 2.0 Liter Displacement

General information

Engine Specifications
Engine code N43B20
Layout Four stroke, Inline-4 (Straight-4)
Fuel type Gasoline
Production 2007-2011
Displacement 2.0 L, 1,995 cc (121.7 cu in)
Fuel system Direct injection
Power adder None
Max. horsepower N43B20K0: 122 PS (90 KW; 121 HP) at 6,000 rpm
N43B20U0: 143 PS (105 KW; 141 HP) at 6,000 rpm
N43B20O0: 170 PS (125 KW; 168 HP) at 6,700 rpm
Max. torque N43B20K0: 185 Nm (18.9 kg·m; 136.5 ft·lb) at 3,000 rpm
N43B20U0: 190 Nm (19.4 kg·m; 140.2 ft·lb) at 4,250 rpm
N43B20O0: 210 Nm (21.4 kg·m; 155.0 ft·lb) at 4,250 rpm
Firing order 1-3-4-2
Dimensions (L x H x W):
Weight

Cylinder block

Cylinder block
Cylinder block alloy Aluminum
Compression ratio: 12.0:1
Cylinder bore: 84.0 mm (3.31 in)
Piston stroke: 90.0 mm (3.54 in)
Number of piston rings (compression / oil): 2 / 1
Number of main bearings: 5
Cylinder inner diameter (standard): 84.000 mm (3.3071 in)
Piston skirt diameter (standard): 83.996 mm (3.3069 in)
Piston ring side clearance: Top 0.020-0.060 mm (0.0008-0.0024 in)
Second 0.015-0.060 mm (0.0006-0.0024 in)
Piston ring end gap: Top 0.150-0.300 mm (0.0059-0.0118 in)
Second 0.200-0.400 mm (0.0079-0.0157 in
Crankshaft journal diameter: 1-4: 56.000 mm (2.2047 in)
5: 65.000 mm (2.5590 in)

Main bearing cap tightening procedure and torque specs:

  • Step 1: 20 Nm (2.0 kgf·m; 14.8 ft·lb)
  • Step 2: Turn all bolts 70°

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing

  • Step 1: 20 Nm (2.0 kgf·m; 14.8 ft·lb)
  • Step 2: Turn all bolts 120°

Lower part of the crankcase block

  • M8x40: 22 Nm (2.2 kgf·m; 16.2 ft·lb)
    M8x26: 22 Nm (2.2 kgf·m; 16.2 ft·lb)

Oil injectors to cylinder blockk

  • 12 Nm (1.2 kgf·m; 8.9 ft·lb)

Cylinder head

Cylinder head
Valve Arrangement: DOHC, chain driven
Valves: 16 (4 valves per cylinder)
Intake/Exhaust duration:
Valve head diameter: INTAKE
EXHAUST
Valve steam diameter: INTAKE 6.000 mm (0.2362 in)
EXHAUST 6.000 mm (0.2362 in)

Head tightening procedure and torque specs:

M10x170

  • Step 1: 30 Nm (3.1 kgf·m; 22.1 ft·lb)
  • Step 2: Turn all bolts 90°
  • Step 3: Turn all bolts 90°-
  • Step 4: Turn all bolts 45°

M9x95, M9x125

  • Step 1: 30 Nm (3.1 kgf·m; 22.1 ft·lb)
  • Step 2: Turn all bolts 90°
  • Step 3:
  • Step 4: Turn all bolts 45°

Maintenance data

Compression pressure
Standard 10.0 bar (145 psi) or more
Oil system
Oil consumption , L/1000 km (qt. per miles) Up to 0.7 (1 qt. per 850 miles)
Recommended engine oil SAE 5W-30, 5W-40
Oil type BMW Lognlife-04
Engine oil capacity (Refill capacity) 4.25 L (4.49 US. qt, 3.74 Imp. qt.)
Ignition system
Spark plug NGK ZKBR7A-HTU

Vehicle applications

Model Years Produced
BMW 116i (E81/E87) 2007–2011
BMW 118i (E81/E87/E88) 2008-2011
BMW 318i (E90/E91/E92/E93) 2007-2011
BMW 120i (E81/E82/E87/E88) 2007-2011
BMW 320i (E90/E91/E92/E93) 2007-2011
BMW 520i (E60/E61) 2007-2009
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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