Audi's R18 e-tron quattro endurance racer has been thoroughly revised for the 2015 season, with efficiency being the dominating theme of this year's LM P1 car.
Audi has long been a believer in hybrid race cars, and has won the Le Mans round of the World Endurance Championship since 2012 with its diesel-electric R18 e-tron.
In 2015, the company's racing arm Audi Sport aims to retain the Le Mans crown by employing wide-ranging efficiency and powertrain tweaks.
Key among these is the increased output of the R18's hybrid driveline, which moves the car up a power class to the 4-megajoule category.
That means the R18 can now pump out up to 4 megajoules of recovered electrical energy per lap of the 13.6km Circuit de la Sarthe, though it comes with the penalty of a reduced fuel allowance - 2.5 percent less fuel per lap, to be exact.
Still, with the electric drive motors now capable of churning out 200kW - significantly more than last year's car - and the battery now able to store up to 700 kilojoules of energy recovered during braking, the 2015 R18 should be able to get extract more go from each drop of diesel it takes on.
Despite the changes, the R18 still hits the LM P1 class minimum weight of 870kg.
The R18's four-litre turbo diesel V6 now makes 410kW (an increase of 15kW), and power from the combustion engine is taken to the rear wheels. The front wheels are powered by the electric drive motors, giving the R18 e-tron quattro an all-wheel drive capability.
Meanwhile, substantial changes to the exterior have been made to improve cooling and aerodynamic performance. Vent placement and ducting for the R18s radiators have been optimised to reduce drag, and have necessitated changes to the car's LED headlamp array.
The 2015 R18 will also have the ability to swap its bodywork between two designs: a low-drag, low downforce version for faster circuits and a higher-drag, high-downforce version for tighter, twistier tracks.
Audi's decision to bump the R18 up into the 4-megajoule class means this year's racer will need to be a more efficient machine than before, but with the benefit that less fuel (and thus less weight and shorter refuelling times) needs to be carried.
Its strategy is by no means as extreme as that of Nissan and its GT-R LM Nismo FWD LM P1 car (which belongs in the 8-megajoule class), but with Audi's strong track record in endurance prototype racing should put it in good stead for this year's season.