BMW B48 Engine — The Modern Four-Cylinder Turbo

Overview

The B48 is BMW's modular 2.0-liter turbocharged four-cylinder, replacing the N20 from 2015 onwards. Part of the same modular family as the B58 (six-cylinder) and B38 (three-cylinder), sharing the 500cc-per-cylinder architecture.

Specifications (B48B20):

• Displacement: 1,998 cc
• Bore x Stroke: 82.0 mm × 94.6 mm
• Compression: 11.0:1
• Power: 184-258 hp depending on variant
• Torque: 300-400 Nm
• Turbo: Single twin-scroll
• Injection: Direct (TU0) or Dual direct+port (TU1)

Key Improvements over N20

• No timing chain issues — robust duplex chain, front-mounted
• Modular design — shared tooling with B38/B58
• Higher compression — 11.0:1 vs 10.0:1
• Longer stroke — more torque-oriented
• Dual injection (TU1) — eliminates carbon buildup

Variants

Code	Power	Torque	Application
B48B20A	184 hp	300 Nm	320i
B48B20B	258 hp	400 Nm	330i
B48B20O1 (TU1)	245-258 hp	400 Nm	330i (2019+)

Common Issues

The B48 is significantly more reliable than the N20:

1. Coolant Loss

• Some B48s experience slow coolant loss
• Usually thermostat housing or hose connection
• Fix: Pressure test, replace faulty component

2. Oil Consumption

• Some units consume oil, especially early production
• Monitor oil level between services

3. Turbo Wastegate Noise

• Minor rattle at idle on some units
• Usually not a reliability concern

Tuning

Stage	Power	Torque
Stock (330i)	258 hp	400 Nm
Stage 1	300-320 hp	460-480 Nm
Stage 2	340-360 hp	500-530 Nm

The B48 is a solid, modern engine that fixed the N20's biggest problems. It's not as exciting as the B58 but it's efficient and reliable.