Caterham’s new Seven 170 is now available to order in the UK as a complete kit or a factory build with prices starting from £22,990. The lightest Caterham model ever produced, the new model builds on the foundations of its predecessor, the Seven 160, by complying with Japanese Kei car regulations.

That means the 170 comes with a 660cc turbo-charged Suzuki engine, which produces 84 bhp and 86 lb-ft of torque. It might not sound like much, but when the car can weigh as little as 440 kg depending on specification, it’s enough for a power-to-weight ratio of 170 bhp per tonne.

The miniscule weight is partly down to the compact dimensions. No Seven is large, but the 170 is the smallest model in the range. With a total width of 1.47 metres, it’s 105 mm narrower than anything else in the Caterham stable. And with a 155-section tyre and a live rear axle, Caterham says “drivers of all capabilities” can extract “the full potential” from the car.

Caterham Seven 170

And the full potential is substantial, thanks to that lack of weight. The sprint from 0-62 mph takes just 6.9 seconds and the top speed can rise above 100 mph, putting the 170 on a par with warm hatchbacks such as the Kia Ceed GT, despite its 0.66-litre engine.

The reduced weight also means the 170 is among the most efficient cars Caterham has produced. With official CO2 emissions of 109 g/km, the 170 is the least polluting model ever built by the British car maker.

As well as choosing whether to build the car or have it built by the factory, customers also get a choice of S or R trim levels. The S is the more laid back version, with a five-speed gearbox, road suspension and 14-inch silver alloy wheels. Black leather seats also feature alongside a Momo steering wheel and a choice of four paint colours, while a full windscreen and wet-weather gear including a hood and side screen are also thrown in.

Opt for the R and you get the same five-speed gearbox, but you also get a sport suspension pack, black alloy wheels and composite race seats. You also get a four-point race harness, a limited-slip differential and a carbon-fibre dashboard.

“The Seven 170 really distils the brand’s reputation for offering accessible, simple, light-weight sports cars,” said Caterham CEO Graham Macdonald. “Given the popularity of the 160, we’re really excited by the potential the Seven 170 offers customers.

“We’ve taken what was great about the 160, its performance and competitive price, and built on it by adding even more choice for our customers. We’re confident the inclusion of the 170R, not previously available on the 160, will prove a hugely popular specification for both new and old customers.”

Gallery: Caterham Seven 170