Engine and gearbox
The Audi Q8’s 3-litre V6 turbo diesel engine is supplemented by a 48-volt belt-driven small electric motor mounted on the front of the engine. Its main use is to aid the diesel engine under load to reduce turbo lag, but it also acts as a starter motor to smooth out the car’s start/stop function and adds charge to the 48V sub-system’s lithium-ion battery.
When it comes to actually reducing lag, though, it’s not entirely successful. Press the throttle below 2500rpm and there is a significant pause before the car responds and eventually surges forward. It isn’t any worse than you would reasonably expect from a diesel SUV, but the promise of less lag from the mild hybrid system and that the Q8’s engine is very responsive above 3000rpm, and the delay you get at low rpm is rather disappointing. As is the 5000rpm red line that the engine won’t rev to; instead the gearbox changes up automatically, whether you’re in manual mode or not, at 4900rpm.
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These are the only criticisms of the Q8’s drivetrain, though; its performance is more than adequate, it’s very smooth and refined, its eight-speed automatic gearbox makes almost seamless shifts, the quattro system distributes torque to all four wheels without any fuss, and if you get a hint of noise from the engine it’s actually rather pleasant – not the rattly diesel sound you might have anticipated.