What is it?
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.