June 25, 2008 Porsche has announced the launch of all-wheel drive models of its 911 Carrera 4 and 4S sportscars, including an engine, gearbox and drivetrain makeover that the company claims delivers up to 8.5% more power, 12.5% better gas mileage, and over 15% less CO2 emissions than the models they replace.

Both new Porsches feature direct-injected flat six engines. The 911 Carrera 4's 3.6 litre engine gains 15kW for a total of 254kW - and the higher spec 4S makes an extra 22kW to 283kW and gets around 22 miles to the gallon.

The fully electronically controlled all-wheel-drive system, taken from the 911 Turbo and modified to suit, is heralded as a big step forward over the old multi-plate clutch system in terms of stability, traction management and handling.

Both AWD sportsters come standard with a 6-speed plus reverse manual transmission - and as an alternative Porsche offers the new PDK double-clutch electro-hydraulic automatic. The PDK auto system shifts exceptionally quickly between its seven forward gears - so quickly that there's absolutely no interruption to acceleration during a gear change, which reduces wasted engine revs and boosts economy over the manual.

Other updates include bi-Xenon lighting, LED daytime driving lights, LED tail-lights and the option of dynamic bending headlights, in which the headlights follow the steering to better illuminate the road as you drive around corners.

Interior-wise, the Porsche Communication Management touch-screen system has a new user interface for easier access to navigation, info and audio systems - and the system now supports Bluetooth, USB and iPod interfaces.

The new Carrera models will debut in both Coupe and Cabriolet versions and are expected to go on sale in September.