BMW N43B20

The 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

Cylinder block

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

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

Vehicle applications

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