BMW's new four-cylinder to replace classic six

BMW will fire the first shots in an upcoming prestige four-cylinder engine war when it replaces its classical straight-six with a turbo-charged four pot by the middle of this year.

The new petrol engine, dubbed N20, will soon debut in the X1 -- just weeks ahead of finding a home in everything from the X3 to the Z4 and even the 5-Series. Combining direct fuel injection, twin-scroll turbo-charging and variable valve timing and lift, the N20 engine will boast 180kW of power and 350Nm of torque.

While its European debut will be within the engine bay of the X1, it will also be strong enough to become the first four-cylinder BMW sold in the United States since the 1998 318i when it arrives in the Z4 SDrive 28i in September.

Having four cylinders won't make it slow, and BMW claims the X1 xDrive 28i will punch to 100km/h in 6.1 seconds (or 6.5 with the eight-speed auto) on its way to a 240km/h top speed. The lighter Z4 will be even quicker, and BMW sources expect a 0-100km/h sprint in the low five second bracket.

It's also more economical than the basic six-pot it replaces, with BMW claiming 7.9 litres/100km on the combined cycle for an average of 183 grams of CO2/km.

While the 3-Series is an obvious candidate for the N20, it is too deep into its model cycle for BMW to bother investing in the production engineering for it, so it will have to wait for the next, all-new 3-Series.

For the US, limited production capacity in the X1's Leipzig factory has pushed the X1's arrival out from the scheduled Spring date to the last quarter of the year -- at the earliest.

Heavily based around the 3.0-litre six-cylinder TwinPower engine (pictured), the new powerplant will, initially, arrive as a 1997cc with enormous flexibility.

While its peak power will arrive at 5000rpm, it delivers its peak torque from an incredibly diesel-esque 1250rpm. It uses an all-aluminium crankcase and a 10:1 compression ratio, combined with a heavily oversquare architecture to generate a 90.1 kW/litre specific power output.
 

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