These are the first pictures of the new Mercedes S400 BlueHybrid. With a combined economy figure of 35.8mpg and a CO2 rating of just 190g/km, Mercedes claims it is the world’s most economical petrol-powered luxury saloon.
But put your chequebook away – it’s not coming to the UK. The BlueHybrid has been developed primarily for the diesel-disliking US market, where its green credentials and upper-echelon image should make it a massive hit for buyers looking to downsize their fuel bills without affecting their status. And of course, when it goes on sale in summer 2009, it will also have extensive pan-European appeal.
How does this Mercedes S-class BlueHybrid work?
A pancake-shaped electric motor sits between the engine and the modified seven-speed automatic transmission. It’s an advanced three-phase AC external rotor magneto motor, which develops 20bhp and 118lb ft of torque while operating at 120V.
As well as acting as a starter and generator for stop-start work in urban areas, the motor also recaptures lost energy during braking and when coasting. This recouped energy is stored in the Mercedes’ bespoke lithium-ion battery.
Compact and developed specifically for automotive applications, this sits in the engine compartment where the traditional lead-cell battery would normally be housed. As well as supplementing the powertrain, it also powers the on-board electrical systems through an integral 12V transformer.
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The car’s 3.5-litre V6 has also been heavily modified for this application. It’s fitted with a new cylinder head, reworked pistons and it breathes through a new variable valve control set-up where the intake valve is kept open slightly longer between the intake and compression phases to boost thermal efficiency and reduce untreated emissions. And because the battery pack and electric components are fully integrated, cabin and boot space are unchanged.
The result is a 1955kg limousine with a combined petrol-electric output of 299bhp and 283lb ft – enough to hit 60mph in 7.2 seconds, top out at 155mph, cover 700 miles between refills and emit just 190g/km – a CO2 rating better than a Mercedes C230.
And Mercedes claims the green S400 is particularly frisky through the gears because the torque developed by the electric engine kicks in instantly, irrespective of engine revs. But then you can say the same about any electric car.
The figures are indeed impressive – for a petrol engine. But it only takes a cursory glance at the specifics for the S320 CDI (34mpg, 7.5 seconds, 155mph) to see that the regular S-Class diesel can pretty much match the S400 BlueHybrid.
Where the S400 does win hands-down though is its paltry 190g/km CO2 rating – significantly lower than the diesel’s 220g/km. There’s no word on pricing, but expect the BlueHybrid to sit between the S350 and S500 – which means about £65,000 in today’s money.
Mercedes UK is pushing hard for right-hand drive versions of the S400 BlueHybrid, but given the engineering costs of conversion it looks like it will be 2010 before the big hybrid arrives here in right-hand drive – well after the facelifted S-class arrives in mid-2009.
Would you take an S400 BlueHybrid over a diesel S-class or an Lexus LS600h? Click 'Add your comment' below and have your say