What is it?
A limited-run homologation special of BMW’s world touring car. A mere 2600 will be made available worldwide, and only 500 will be coming to the UK.
Based on the 320i M Sport, the suspension, gearbox, bodywork and interior are all carried over unchanged. The areas that have been tweaked include the wheels (unique 18s), brake discs (now 300mm all round), and most significantly the engine, which is hand-built specifically for the 320si with more power and a very different character from the regular version. It may be stretching the point to call this a latter-day four-cylinder M3, but it’s well on the way.
The 320si engine is no mildly tweaked version of BMW’s regular 148bhp 1995cc unit. It has been engineered to rev higher; the bore is up by 1mm to 85mm and the stroke down by 2mm, to 88mm, while the induction and exhaust valves are all bigger, too. The compression ratio is up from 10.5:1 to 11.0:1, cylinder liners are aluminium alloy rather than cast iron, and there’s no Valvetronic induction system. The cylinder head is cast alongside BMW’s F1 engines.