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BMW N42B20 Engine (Design, Issues & Tuning)

Updated: Feb 2

✔ This article has been fact checked.

The BMW N42B20 is a DOHC four-cylinder petrol engine manufactured between 2001 and 2004, it replaced the BMW M43. Its 2L displacement yields 141 horsepower and 200 nm of torque.

N42 engines have a DOHC valvetrain, VANOS (variable valve timing), and an aluminium engine block compared to its M43 forerunner. It also had Valvetronic (variable valve lift) for the first time in a BMW engine.

The N42B20 engine was used in the following cars:

  • 2001-2004 E46 318i/318Ci/318ti

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bmw n42b20 engine

BMW N42B20 Engine Design

Instead of having a fully cast iron cylinder block, the engine features an aluminium cylinder block with cast iron sleeves. The engine is therefore substantially lighter than earlier BMW four-cylinder engines.

The cylinder block has been fitted with a brand-new crankshaft, pistons, and connecting rods with a 90 mm stroke. The balance shafts on the N42B20 engine are the same as those on the M43TU engine. Engineers had to make a few changes in order to fit them within the new cylinder block.

The new aluminium cylinder block is topped with a 16-valve DOHC aluminium cylinder head. This is a significant advancement over earlier models, which had 8-valve SOHC heads. Exhaust valves have a diameter of 29 mm, while intake valves are 32 mm in size.

The N42B20 camshaft has a duration of 250/258 degrees and a valve lift of 9.7/9.7 mm. The engine uses the variable valve lift technology known as Valvetronic. The engine has a timing chain added.

The variable valve timing technology is integrated into both camshafts (Double-Vanos). An intake manifold with a variable shape that is electrically regulated is also present. To define this technology, BMW came up with the acronym DISA.

At both high and low rpm, it is intended to deliver optimum torque and power characteristics. A Bosch DME ME9.2 fuel injection system is used.

Engine Specs

  • Manufacturer: BMW Plant Hams Hall

  • Production years: 2001-2004

  • Cylinder block material: Aluminium

  • Cylinder head material: Aluminium

  • Fuel type: Gasoline

  • Fuel system: Fuel injection

  • Configuration: Inline

  • Number of cylinders: 4

  • Valves per cylinder: 4

  • Valvetrain layout: DOHC

  • Bore: 84.0 mm

  • Stroke: 90.0 mm

  • Displacement: 1995 cc

  • Type: Four-stroke, naturally aspirated

  • Compression Ratio: 10:1

  • Power: 143 hp (105 kW) at 6,000 rpm

  • Torque: 148 lb-ft (200 Nm) at 3,750 rpm

  • Firing order: 1-3-4-2

  • Engine oil weight: 5W-30, 5W-40

  • Engine oil capacity: 4.25 litres

  • Oil change interval: 6,000 miles (10,000 km) or 12 months

  • Applications: BMW E46 318i, 318Ci, 318ti