2015 Mercedes-AMG A 45 Renntech 459 Edition

Maybe it’s the comically offensive exhaust. Think reverberant metallic boom, punctuated by a resounding crack on the upshift, and often finished with the cymbal hiss of the dump valve’s release. Or perhaps it’s the styling that – to these eyes at least – has stuck two fingers up at tasteful and gleefully gone on to embrace flamboyancy.

More likely than any of that, it’s the no-prisoners performance served up by the 452bhp, 398lb ft 2.0-litre turbocharged motor.

Regardless of the specifics, the Renntech Mercedes A 45 AMG is an oddly addictive thing.

For £3599, the Nürburgring-based tuners will take your stock A 45 AMG, update its software, put a bigger turbo on that boosts pressure up from 1.85 to 2.05bar and deliver you a car that will do 0-62mph in 3.9sec and strop right on to a faintly ludicrous 186mph. That’s improved from 4.6sec and a limited 155mph in the (hardly faint-hearted) standard A 45 AMG, which produces a mere 355bhp and 332lb ft.

Naturally, Renntech will upgrade the chassis and brakes, too. For £2050 including fitting, you get a set of Pagid brake pads and Bilstein coilovers (tuned and set up by Renntech) in the softer of two available set-ups, catchily titled the ‘Fast Road B16’ package. Opting for the firmer Clubsport set-up, as fitted to our test car, will cost a further £1626. Finally, our car also came with Renntech’s sports exhaust downpipe and catalytic converter, at £1935. At least the trick Dunlop tyres are thrown in for free.

You can opt out of the carbonfibre bonnet and garish decals if you wish, and the £6000 19in forged alloys that our car sits on are also probably an unwise expenditure. 

It’s hard not to look at the Renntech A 45 and immediately expect it to be something that’s way over the top for UK roads, but the creation isn’t as monstrous in practice as it first appears.

The dampers are a particular success. Yes, they’re firm enough that you’ll get lots of short-frequency vertical movement in town or over undulating country roads. More importantly, however, the actual bump absorption and resistance to awkward cambers is effective and sophisticated enough that it keeps the car from skittering over fast mid-corner bumps or jarring uncomfortably over potholes. Stick the seven-speed dual-clutch automatic gearbox in Comfort in order to tame the exhaust and, although tyre and engine noise are still a background hum, the Renntech A 45 is also an acceptable long-distance commuter.