Things have been busy as renowned BMW tuner AC Schnitzer’s Aachen HQ: the company has two new vehicle packages ready for display at the 2011 Geneva auto show that will open next week.Focusing on the F10 5 Series and latest Z4, Schnitzer has prepared a light convertible and pseudo M5 sedan package for public debut on its display stand in Geneva.TURBODIESEL Z4?Starting with the Z4, which Schnitzer has renamed the 99d, the company’s technicians have done the unusual and transplanted a 320d turbodiesel engine into A Z4l. Why? To achieve the best-possible combination of performance and economy, a rather noble aim for a company traditionally given to making cars faster and heavier on fuel. With the Z4 lightened by an amazing 230kg and power boosted (negligibly) from 135 to 140kW, Schnitzer claims it consumes only 3.8 litresl/100km with its CO2 emission signature at a low 99g/km - hence the 99d nameplate. Moving on to the company’s new 5 Series offering: here is the ACS5 Sport S, a tuned 550i which is more Schnitzer’s traditional fare.GOOD FOR 320KM/HThanks to a raft of electronic engineering trickery (relaxing the engine’s control parameters) and less-strangling exhaust plumbing, Schnitzer’s technicians have liberated an additional 97kW from the twin-turbo, 4.4-litre, V8. Powering up to 397kW, supported by 720Nm of torque, and featuring a proper mechanical limited-slip rear differential, Schnitzer says its ACS5 Sport S is good for the benchmark 0-100km/h sprint in a time of only 4.5sec. At the long end of its eight-speed ZF transmission’s endurance the ACS5 Sport S has recorded a speed of 320km/h during testing. Despite their very different performance profiles (economy versus sheer speed) the 99d and ACS5 Sport S are both set to retail for similar money, a rather substantial R1.5-million. Not really great value for a M5 knock-off? Perhaps.Obscenely overpriced for 140kW of diesel powered Z4? Very much so. More 2011 Geneva auto show reports.