ARIEL ATOM 4RR

Ultra-lightweight track toy's 25th birthday gift is an astonishing 525bhp

- MATT PRIOR

Ariel calls this its “most extreme performance machine ever”, which is some claim given that it once put a 500bhp V8 into an Atom.

But this is the 4RR - created to celebrate 25 years of Atom production - whose Honda Type R-sourced turbo four has been turned up to eclipse even the Hartley V8’s output, making 525bhp at 8200rpm and 406lb ft of torque at 5200rpm. I remember the Atom V8 being the most ferociously accelerative production car I had driven back in 2011. At 657kg, the 4RR is a bit heavier, but we're still talking about a power-to-weight ratio of 799bhp per tonne - or more than you got in a Bugatti Chiron Super Sport.

The engine gets forged pistons and conrods, a lightened flywheel, bespoke camshafts, an uprated valvetrain with revised port geometry, and a race-grade head gasket and cylinder head studs. There's a high-pressure fuel system, a bigger turbo that boosts to 1.7 bar and a higher-flow oil system.