Caterham has unveiled its lightest ever production car – the Seven 170. The new car is the firm’s first since it was acquired by Japan-headquartered automotive group, VT Holdings.

A follow-up to the Seven 160 that debuted in 2013, the Seven 170 features the same mechanical layout and a 660cc turbocharged three-cylinder from Suzuki designed to meet Japan’s domestic kei-car regulations, which put a limit engine size, power output and a car’s overall dimensions in return for cheaper road tax and insurance. Like the Seven 160, the new model qualifies as a kei car at least in size, measuring 1470mm wide – 105mm narrower than anything else within Caterham’s current range.

However, while 63bhp is the maximum output for a kei car, the engine in the Caterham Seven 170 has been tuned to 84bhp. That may not sound like much, but it’s more than twice that of the 1957 Lotus Seven; as the car weighs only 440kg, that means a power-to-weight ratio of 170bhp per tonne. The car also has a live axle and modest 155-section tyres for extra purist points.

Prices start from £22,990 in kit form, with the Seven 170 available in S and R variants. The latter gains a sports suspension pack, 14-inch black alloy wheels, limited-slip differential, a carbon fibre dashboard, composite race seats and four-point harnesses for an additional £1000.