Performance and 0-60 time
A familiar trope of the automotive journalist is that a well-driven hot hatchback could show a supercar a clean pair of heels on a tricky, winding back road. Back in the 1990s when the genre was at a low ebb thanks to insurance premiums this was hard to believe; with 376bhp and four-wheel drive at its disposal, the A45's ability to humble even the modern generation of supercars on tight, technical roads looks a lot more likely.
In terms of pure performance, the A45 is impressively fast. Mercedes quotes a 0-62mph sprint of 4.2 seconds, and when we timed it to just 60mph it reached the speed in 3.9sec.
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Thanks to the car's launch control mode (hold the brakes, press the stability control button, switch the transmission to manual mode, pull both paddles, pull the right paddle to confirm, floor throttle, release brake, and breathe), it's also endlessly repeatable.
The engine is punchy from low revs and really flies once the tachometer needle passes 2500rpm. Unfortunately, the 7-speed dual-clutch transmission hinders it a little - reaction to tweaks of either paddle is a little too slow, particularly when changing down the 'box. More satisfying, if puerile, is the pop accompanying each full-bore upshift, and it's cacophonous at other times too. First versions of the A45 made a long flatulent parp with every gear change, but it’s now a much more pleasing short sharp crack.
As well as the thunder from the exhaust, the AMG’s engine starts with an industrial chunter and idles with a burble, and brisk acceleration is always accompanied by a hard-edged rasp.
Power delivery is surprisingly linear for such a highly-strung engine, with little of the lag you'd expect from a heavily turbocharged unit. In some respects, it makes the A45's searing speed feel almost normal - there's no distinct rush of acceleration, rather a relentless gathering of pace.