Less is more with Merc’s new SL400Comment on this story
Stuttgart, Germany - Mercedes-Benz has announced a new SL two-seat roadster - the SL400 - to replace the current 3.5-litre SL350 V6. But far from being a four-litre V8 (we couldn't help fantasising about a rev-happy, short stroke version of the SL500) the SL 400 is actually half a litre smaller than the engine it replaces.
It's a 2996cc biturbo V6, marginally oversquare at 88 x 82mm, running maximum boost of 1.8 bar. Spray-guided combustion controlled by piezo-electronic direct fuel-injectors delivers as many as five injections per powers stroke at fuel pressures of up to 200 bar.
This third-generation direct injection system is supplemented by rapid multi-spark ignition; after the initial spark and a brief combustion period, the 'stick' coil (there's one in each spark plug cap) is recharged very rapidly and a further spark is discharged - as many as four sparks in succession within one millisecond, creating a flame front with a larger spatial expansion than conventional ignition.
By varying the timing and duration of the sparks both the timing and the rate of combustion can be controlled to reduce detonation promote cleaner, more complete combustion.
The SL400 kicks out 245kW (20kW more than the 350) at 5250rpm and a muscular 480Nm - a 110Nm improvement on its predecessor - from 1600 - 4000rpm, launching the all-aluminium roadster from 0-100 in just 5.2 seconds and on to an electronically limited 250km/h, at a quoted combined-cycle cost of 7.2 litres per 100km and 172 g/km of CO2.
The SL400 will be released in South Africa in July 2014; prices, as always, when they get here.