BMW 316 E90 N45B16 Engine
R21,500.00
The BMW N45B16 is a 1.6-litre, naturally aspirated, inline 4-cylinder petrol engine produced between 2004 and 2011. It was developed specifically to power the entry-level baseline models in markets with high displacement-based taxes or strict insurance brackets, most notably found in the pre-facelift BMW E90 316i and early E87 116i.
Unlike its companion engine of the era—the N46—the N45 is a simpler, high-revving unit built with old-school mechanical traits rather than advanced throttle-less valvetrains.
Core Engineering Design
The N45B16 represents an interesting engineering choice by BMW, as it stripped away some of the brand’s premium electronic valvetrain technologies to reduce manufacturing costs and physical complexity.
- No Valvetronic Technology: This is the most critical design feature of the N45. While the standard 2.0-litre engines of this era (like the N46) featured BMW’s complex Valvetronic variable valve lift system, the N45 completely omitted it. It relies entirely on a traditional mechanical throttle body to control engine airflow, meaning it has a simpler cylinder head layout with fewer moving parts.
- Dual VANOS: Despite lacking variable valve lift, the N45 does retain fully variable valve timing on both the intake and exhaust camshafts (Double VANOS). This helps the engine maximize its limited displacement by altering camshaft positions on the fly to smooth out the idle and optimize mid-range torque.
- Aluminium Block and Head: The engine features an all-aluminium construction to keep the front end of the E90 as light as possible, retaining BMW’s signature 50:50 chassis weight distribution.
- Short-Stroke Geometry: The engine configuration features a relatively large 84 mm bore combined with a short 72 mm stroke, giving it a high-revving character.
Technical Profiles
| Specification | Metric Value | Imperial / Standard Value |
|---|---|---|
| Engine Code | N45B16 / N45B16A | N45B16 / N45B16A |
| Displacement | 1,596 cc | 1.6 Litres |
| Bore x Stroke | 84.0 mm x 72.0 mm (Short stroke) | 3.31 in x 2.83 in |
| Compression Ratio | 10.2:1 | 10.2:1 |
| Valvetrain | DOHC, 16 Valves, Dual VANOS, Chain Driven | DOHC, 16 Valves, Dual VANOS, Chain Driven |
| Fuel System | Bosch Motronic ME9.2 Multi-Point Injection | Multi-Point Port Injection |
| Aspiration | Naturally Aspirated | Naturally Aspirated |
Performance Output (E90 316i Application)
Because of its small displacement and lack of forced induction, the N45B16 is severely underpowered for a heavy chassis like the E90 3-Series. It requires the driver to work the gearbox hard and rev the engine past 4,000 RPM to make meaningful forward progress.
- Power Output: 85 kW (114 hp / 115 PS) at 6,000 RPM.
- Torque Output: 150 Nm peaking relatively high in the rev range at 4,300 RPM.
- E90 Applications (2005–2007):
- BMW E90 316i Sedan (Pre-facelift global models)
(Note: In late 2007, the N45B16 was largely phased out in the E90 316i in favour of the newer N43B16 engine, which added direct fuel injection to improve fuel efficiency).
Critical Maintenance & Failure Points
While omitting Valvetronic eliminated a major electrical failure point, the N45 shares several structural weaknesses with BMW’s other 4-cylinder engines of the 2000s:
- Timing Chain Slippage & Guide Failure: The single-row timing chain is prone to stretching over time, especially if oil changes are skipped. Compounding the issue, the plastic timing chain guides become brittle from heat cycles and snap. When the guides shatter, the chain slackens, causing it to jump timing teeth, which results in instant valve-to-piston contact and catastrophic engine destruction. A distinct “rattling” sound on cold starts is the primary warning sign.
- VANOS Solenoid Clogging: The Dual VANOS solenoids at the front of the cylinder head feature tiny oil screens. If oil servicing is neglected, sludge gums up these solenoids, triggering a sluggish throttle response, flat spots during acceleration, and persistent “Check Engine” lights for camshaft timing advanced/retarded errors.
- Vacuum Pump Oil Leaks: The mechanical vacuum pump is driven off the back of the exhaust camshaft, positioned directly above the hot exhaust manifold. The internal rubber O-rings harden and leak engine oil onto the hot exhaust pipe, creating a distinct burning oil smell inside the cabin through the AC vents.
- Brittle Plastic Coolant Flanges: The cooling system relies heavily on plastic connectors, including a notorious cooling flange mounted to the rear of the cylinder head against the firewall. This plastic grows brittle and snaps unexpectedly, leading to a sudden, complete loss of engine coolant and immediate risk of head gasket failure.