BMW N20 engine explained: the turbo four, its timing chain and care

The BMW N20 is a 2.0-litre turbocharged four-cylinder petrol engine used from 2011 to around 2017. It replaced many six-cylinder engines in models such as the 328i and 528i, offering similar performance with lower fuel consumption.

In this guide we explain how the BMW N20 works, which models use it, the timing chain issue that many owners ask about and how to keep the engine healthy.

What the BMW N20 is

The N20 was BMW's move towards smaller turbocharged engines. Instead of a naturally aspirated six, it uses four cylinders, a turbocharger and direct injection to produce strong torque from low revs.

The engine has an aluminium block and head, a twin-scroll turbocharger, high-precision direct injection, Valvetronic variable valve lift and double VANOS. Balance shafts help it run smoothly.

This combination gave the N20 a wide spread of torque and good fuel economy. Our articles on BMW Valvetronic and BMW VANOS explain those systems in more detail.

BMW N20 versions and power

The N20 was offered in several outputs:

• Around 156 to 184 PS: used in models badged 18i, 20i and similar.
• Around 245 PS: used in models badged 28i, such as the 328i and 528i.

Both main versions offer around 270 to 350 Nm of torque, available from low engine speeds. In some markets, a related N26 version was used to meet stricter emissions rules.

The real-world performance of the 245 PS version is close to the older 3.0-litre naturally aspirated six, but with less fuel used in everyday driving.

Which BMWs use the N20

The N20 appeared in many models from around 2011:

• F30, F31 and F34 3 Series: 320i and 328i.
• F32, F33 and F36 4 Series: 420i and 428i.
• F10 and F11 5 Series: 520i and 528i.
• F20 and F21 1 Series and F22 2 Series: 125i, 220i and 228i.
• X1 E84, X3 F25, X4 F26 and the Z4 E89 with the sDrive20i and sDrive28i.

From 2015 BMW began replacing it with the B48. Our article on the BMW B48 engine explains the successor.

The BMW N20 timing chain issue

The best-known N20 problem involves the timing chain. On many earlier engines, the plastic chain guide could wear or crack over time. As the guide wears, the chain becomes looser and may start to make noise.

The typical warning sign is a whining or rattling noise, often most noticeable at start-up or at certain engine speeds. If ignored, a broken guide can let the chain jump, which can cause serious engine damage.

BMW revised the parts during production, and many engines have since had the timing chain and guides replaced. When buying, ask for proof of this work. Our article on BMW timing chain problems explains the symptoms in detail.

Other common N20 problems

Besides the timing chain, owners report some other typical issues:

• Oil leaks from the oil filter housing gasket and the valve cover. Our article on the BMW oil filter housing gasket explains this common leak.
• Electric water pump and thermostat failures as the car ages.
• Crankcase ventilation and hose problems, which can affect idle and oil consumption.
• Ignition coils and spark plugs, which need regular replacement on turbo engines.
• Carbon build-up on the intake valves, a typical issue for direct-injection engines.

None of these is unusual for a modern turbo engine, but they should be considered when buying. A pre-purchase inspection by a BMW specialist, with a scan of the fault memory, is a good way to find them early.

How to keep a BMW N20 healthy

Good maintenance is the best protection for an N20:

• Change the oil more often than the long official interval, using a BMW-approved oil. Clean oil helps the timing chain and the turbo.
• Listen for timing chain noise and act early if you hear a whine or rattle.
• Replace spark plugs on time. Our article on BMW spark plugs explains why.
• Warm the engine up gently before driving hard and let the turbo cool after a hard drive.
• Keep records of all work, especially the timing chain.

An N20 with the updated timing parts and a good service history is a strong, efficient engine for everyday driving.

BMW N20 at a glance

Item	Details
Engine type	2.0-litre turbocharged four-cylinder petrol
Production	2011 to around 2017
Power	Around 156 to 245 PS
Technology	Twin-scroll turbo, direct injection, Valvetronic, double VANOS
Main cars	F30 328i, F10 528i, F22 228i, X1, X3, Z4
Known issue	Timing chain guide wear on many earlier engines
Warning sign	Whining or rattling noise from the engine
Successor	B48

Frequently asked questions

What is the main problem with the BMW N20?

The best-known issue is wear of the plastic timing chain guide on many earlier engines, which can cause noise and, if ignored, serious engine damage.

Which BMWs have the N20 engine?

Many 20i and 28i models from around 2011 to 2017, including the 320i, 328i, 428i, 528i, 228i, X1, X3, X4 and Z4.

How much power does the N20 have?

Depending on the version, around 156 to 184 PS for the lower outputs and around 245 PS for the 28i models.

How do I know if my N20 timing chain was replaced?

Ask for invoices or the service history. A specialist can also check the engine and listen for typical chain noise.

What replaced the BMW N20?

The B48, a newer 2.0-litre turbo four introduced from 2015, which is part of the modular BMW engine family.

Sources

• BMW Group – engine technology information
• BMW owner's manuals – F30 and F10
• Workshop experience with BMW four-cylinder engines