Big issues

摘要

V12 engines are big. But are they bad? Two AE writers start from Audi's V12 (right) and look at green and weight issues. Against industry trends to downsize, Audi and BMW's large capacity V12 engines both embody some of the latest in powertrain technology, albeit to different ends. Audi's six-litre diesel offering follows on from the Le Mans winning R10 TDI race engine and will be used initially in the Q7 Quattro SUV, making this the most powerful diesel car in the world. Two turbochargers and a common rail piezo injection system pressurised to 2000bar see the new engine, currently undergoing pre-production testing, develop 500PS at 4000rpm and 1000Nm from 1750-3000rpm. This torque figure eclipses the 650Nm of the 4.2 litre V8 TDI from the luxury A8 and even the 750Nm from the 5 litre V10 TDI fitted to the VW Touareg SUV. Thus equipped, performance of the V12 Q7 is startling: 0-62mph takes only 5.5s before reaching a limited maximum speed of 155mph. A revised exhaust gas recirculation (EGR) system and a diesel particulate filter (DPF) allow the new engine to meet Euro V emissions standards, due in 2010. Fuel consumption on the EU combined cycle is 23.7mpg.