BMW 3 Series 320si Engine Replacement Compare Prices & Get Quotes

A BMW 3 Series 320si engine replacement typically costs £2,500-£4,500 for a rebuilt unit supply-only, or £3,500-£6,000 fitted by a specialist. Used engines start from around £1,200-£2,500, while reconditioned units range from £2,200 to £3,500.

• Prices are significantly higher than standard 320i engines due to the N45's rarity
• Rebuilt engines carry a 12-month unlimited-mileage warranty
• Supply & fit adds £500-£1,000 in labour due to specialist requirements

The 320si uses a completely unique N45B20A engine, not an evolution of the standard 320i's N46 or N43. Differences include: increased bore (85mm vs 84mm) and shortened stroke (88mm vs 90mm); higher 11.0:1 compression ratio; larger valves and wilder camshafts; no Valvetronic system; aluminium alloy cylinder liners; hand-built construction; and a carbon fibre cam cover saving 10kg.

No - a standard 320i engine (N46 or N43) is not a direct replacement for the 320si's N45B20A. The engines have different bore and stroke dimensions, different cylinder heads, different engine management, and different ancillaries. Fitting a non-original engine will also significantly reduce the car's collector value.

• The N45B20A is a completely unique engine, not a modified N46
• Only an N45B20A is correct for a genuine 320si

Only 2,600 320si examples were built worldwide, with just 500 right-hand drive cars for the UK. The engines were hand-built at BMW's Hams Hall plant alongside racing engines. BMW main dealers have quoted 10-month waits for new engines. Parts supply is extremely limited, and many components are unique to this engine.

• Low production numbers mean limited used engine availability
• Hand-built construction means higher manufacturing costs
• The engine shares components with racing units, not standard road cars

A typical BMW 3 Series 320si engine replacement takes 2-4 days for a specialist workshop, assuming the replacement engine is available. However, sourcing the correct N45B20A engine can take significantly longer due to rarity.

• Allow 2-4 days for supply & fit through a specialist
• Sourcing the correct engine may take weeks or months
• Additional time may be needed if unique parts are required

Every rebuilt and reconditioned BMW 3 Series 320si engine supplied through EnginesMarket carries a minimum 12-month unlimited-mileage warranty. Used engines typically come with a shorter warranty (30-90 days) depending on the supplier - always confirm exact terms before purchasing.

• Rebuilt: 12 months / unlimited mileage minimum
• Reconditioned: typically 6-12 months
• Used: 30-90 days, supplier-dependent