| Next year marks the fiftieth year of Seven production and will see the iconic sports car powered by a new range of engines. The long serving Rover K-Series has been replaced by the Ford Sigma, available in a range of outputs. The base engines are manufactured at Ford’s plant in Bridgend, Wales and then bespoke tuned for Caterham. The performance pedigree of the Sigma unit has been already been proven in Formula Ford.
The all-aluminium K-Series made it a hit with manufacturers such as Caterham and Lotus because of its compact dimensions and light weight; essential for cars like the Seven and the Elise who rely principally on an exceptional power to weight ratio for high performance. But the demise of MG Rover, together with non-compliance with emissions standards has meant that users of the K-Series have had to re-source powertrains from elsewhere.
Caterham, which has a long history with the blue oval, has settled on the Ford Sigma after evaluating more than 80 engines from 19 different manufacturers. Otherwise known as Duratec and more commonly found under the bonnets of the Fiesta and Focus, these engines will provide the benefits of ready supply and Euro IV compliance.
Ansar Ali, Caterham’s managing director, said: “The infrastructure and support afforded to a globally recognised engine like the Ford Sigma allows us to plan for the future and maintain our proud tradition of protecting and developing the Seven for years to come.”
The 1595cc Sigma, like the K-Series before it, has an aluminium cylinder block and head and a 16V DOHC valvetrain. Bore and stroke are 79.0 and 81.4mm respectively and compression ratio a relatively high 11:1. NVH is improved, helped by a structural aluminium oil pan. The torque curve is said to be particularly flat, aiding driveability.
A single 1.6 litre displacement replaces 1.6, 1.8 and 1.8VVC K-Series derivatives, and Caterham will offer the engine in three states of tune: 125bhp (93kW) and 140bhp (104kW) variants will be available from launch, with a 160bhp (119kW) version available in summer 2007. Torque output of the 125bhp unit is 120lbft (162Nm) at 5350rpm; other ratings are not yet available.
The RoadSport 125 model, replacing the current Roadsport 120, has a kerbweight unchanged at 550kg but the extra 5bhp lifts the power to weight ratio to 227bhp/tonne, offering acceleration from 0-60mph in 5.9s; an improvement of 0.3s.
Caterham says that the validation program of the Sigma powertrains is its most rigorous ever, comprising more than 10,000 miles on the road and 1200 on the track.
Ironically, the K-Series is now in production again with Nanjing Automobile Corporation. Renamed the N-Series, it has been made Euro IV-compliant ready to go back into the revived MG TF.
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