It should come as no great surprise that a relatively compact, all-wheel-drive car with more than 400bhp at its disposal is capable of sharp off-the-line acceleration. Mercedes-AMG quotes a 0-62mph time of 3.9sec, which is three-tenths quicker than the old A45 managed, and in A45 S trim as sold in the UK, top speed is 168mph.
The way the drivetrain behaves is more important than the outright acceleration though. On the road, where you can only really use the car’s potential for very short periods of time, there’s actually not a great deal of difference in terms of pure speed to the 302bhp A35 – you can use the less powerful car’s performance more frequently.
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But while the A35’s engine is hardly lacking in response or character, the A45’s more fiery unit feels like someone has turned up the gain on an old tube amplifier. Throttle response is keen from low revs, allowing you to surge forward with little effort, and performance only builds from there. It revs smoothly but there’s a harder edge to the sound than with the A35, while the top-end rush is even greater, really encouraging you to use the last of the revs.
Make sure you’re in at least Sport+ mode and the barking and crackling exhaust adds to the theatre, though there’s perhaps a little too much sound also piped into the cabin for some tastes. Regardless, thundering through the gears feels exciting, and the changes from the dual-clutch box are themselves swift, and AMG’s metal paddles have a satisfying mechanical click to their action.
The brakes are more than up to the task of hauling the A45 S back down from high velocities too. There’s an initial softness to the pedal travel that could perhaps be improved upon (though it does make creeping around at normal speeds a smooth affair), but as is typical with AMGs, power and progression are plentiful thereafter, and with the caveat we’ve not yet carried out sustained lapping on track, fade isn’t an issue