Ariel has introduced the fastest and most powerful Atom ever. It’s called the 4RR, and it features an upgraded 2.0-liter, turbocharged four-cylinder K20C Honda engine making 525 horsepower and 406 pound-feet of torque. It can propel the Atom to 62 miles per hour in just 2.4 seconds and to 100 mph in just 5.1 seconds. Top speed is 175 mph.
It is a bespoke, hand-built engine featuring several components that Ariel replaced, upgraded, and re-engineered. It has closed deck sleeves, bespoke forged pistons and connecting rods, and revised cylinder head and port geometry. Ariel also installed an alloy valve set with improved springs and guides, along with a bespoke camshaft.
It has a competition-grade head gasket, a race-spec gated oiling system with a high-flow oil pump, and a larger turbo. Other enhancements include a carbon air inlet system and a new titanium exhaust. The engine pairs with a Quaife six-speed sequential gearbox. 
Power, Features, & Price
The car has three power maps, in addition to the most potent one. Map 1 produces 400 hp and 280 lb-ft. while Map 2 makes 500 hp and 332 lb-ft. Each engine comes with an individualized dyno graph.
The 4RR comes with adjustable twin-tube Öhlins dampers. Stopping power comes from 12.2-inch, two-piece AP Racing ventilated rotors, the largest that will fit with the Atom’s wheels. Drivers have 11 ABS settings, including an off option. The car wears staggered 16- and 17-inch wheels front and rear, which Ariel wraps in Yokohama A052 tires.
Tell us what you think!
Ariel says it is building the 4RR in “extremely limited numbers.” How limited? The company did not say, but the starting price for this ultimate Atom is £208,000, or $279,472 at today’s exchange rate. Oh, and it is road legal.
The 4RR also celebrates the Atom’s 25th anniversary. Deliveries originally began in 2000.
Motor1’s Take: It’s wild to think the Ariel Atom has been on sale for a quarter century, but it is still here, pushing the boundaries of unmatched fun and performance. There are very few small, lightweight open-cockpit sports cars on the market, but the Atom 4RR has just moved to the top of our bucket list.
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The Ariel Atom 4RR delivers 525 hp and 0-62 mph in just 2.4 seconds for $279,472.
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This ultra-lightweight supercar pushes performance boundaries in the rare open-cockpit sports car segment.
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The 4RR celebrates Ariel's 25th anniversary since the original Atom debuted in 2000.
