Mazda reveals extra-green Sky engines

Mazda is putting the finishing touches to new advanced petrol and diesel engines and manual and automatic transmissions that will bring fuel economy savings of up to 20% in its medium and large cars.

Some of the technology they employ has forced Mazda to develop an all-new platform with an engine bay big enough to take them.

The platform can be adapted for anything from mid-sized hatchbacks and SUVs to larger family cars and MPVs. Mazda is also developing a new suspension system that, it says, will solve the ride and noise issues with some of its current models. More precise electronic power steering is also on the way.

The new engines are called Sky ('because the sky's the limit', says the company's research and development chief, Seita Kanai) and will initially be available as a 165bhp 2.0-litre direct-injection petrol unit and a 175bhp 2.2-litre diesel.

Both will be available with the new six-speed manual or auto gearboxes. More powerful and smaller-capacity versions of the Sky family will follow. All will meet emissions regulations not due to come into force until 2014.

Torquey petrols, smooth diesels
They'll be seen first in the next Mazda 6, arriving in the UK in 2012. The aim was to create a range of petrol engines with something close to the torque characteristics and fuel economy of diesels, and diesel units with the refinement and smoothness of petrols.

Mazda has targeted a CO2 figure of 105g/km for the manual diesel, with fuel economy 20% better than the equivalent 6 today, while the aim for the petrol unit is CO2 emissions of 140g/km and 15% fuel savings.

The petrol develops 144lb ft of torque all the way from 2000rpm to 5500, with a peak of 155lb ft. The diesel, meanwhile is unusual in that it revs to 5200rpm rather than the 4500rpm of most rivals, thanks to an increased spray of fuel delivered at higher pressure, and lighter moving parts. It has a maximum 310lb ft of torque from 2000rpm, although there's smooth acceleration from around 1500rpm.

New drivetrains tested
We've tried all combinations of the new engines and gearboxes in prototypes disguised as current Mazda 6s, and they're impressive in their smoothness and consistent acceleration over a wide rev range. Mazda's claims that the petrol and diesel deliver their torque in a similar way are borne out: the biggest difference is that the diesel has double the torque of the petrol engine.

Both engines have a new space-consuming exhaust layout that disperses waste gases better than a conventional system, for greater efficiency. This, and the need to package the new rear suspension, was partly behind the need for the new platform, which is 20kg lighter than the platform of the current 6, despite being 30% stiffer.

The benefits of the increased stiffness will be improved crash protection and reduced transmission of road noise into the cabin.

The overall weight saving compared with today's 6 is 100kg. Mazda's iStop stop-start system, regenerative braking and new electronc power steering will also be fitted as standard.