It’s doubtful that Colin Chapman could have envisaged such a prolonged shelf life for the Lotus Seven, his greatest gift to petrolheads.
But here we are, shortly to celebrate 50 years of the car which refreshes drivers’ parts other cars can’t reach. And just like Chapman’s first Lotus Seven to fire to life, the latest Jubilee spin-off from Caterham’s Dartford factory features Ford power beneath its flyweight, louvred aluminium bonnet.
It goes without saying that this is a big deal. As the bread and butter offering of the family, the Ford Sigma engine is trading places with that venerable stalwart of the Seven’s history, the Rover K-Series.
No need to spell out why that is. But why Ford’s 1.6-litre Sigma to take its place? Because it’s light, modern, has the delivery characteristics to suit the Seven and is clean – crucial if Caterham is to meet current EU4 emissions regulations – and comes with the R&D muscle of Ford, which will develop the powerplant further to satisfy 2009’s EU5 legislation.
In an age of nanny-state legislation governing the public’s consumption of cars, without Ford’s assistance Caterham’s future would be none too bright. And the world without Caterham would be very dull indeed.
The 1,595cc unit is an all-alloy lump with a cross flow, 16-valve cylinder head and twin overhead camshafts. With a higher compression ratio than the K-Series, and Caterham’s own tweaks – modified inlet cam timing, Caterham throttle body, engine management system and exhaust - your right foot is treated to 125bhp at 6,100rpm and 120lb-ft at 5,350rpm.
That may not sound a great deal but as any seasoned Seven driver will delight in explaining that, in a car weighing 550Kg (in Roadsport 125 trim), it equates to 227bhp per tonne and 0-60mph in just 5.9 seconds.
Move up the scale to the Roadsport 150 and there’s 150bhp at 6,900rpm but a slightly disappointing 120lb-ft at 5,600rpm. which means 270bhp per tonne and 5.0 seconds to 60mph. Do the right thing and tick the Superlight box on the order form and with 300bhp per tonne you’re talking 0-60mph in 4.7 seconds.
Torque about change
Torque is claimed to be the biggest single improvement over the K-Series, and it has to be said the 1.6-litre engine is flexible, pulling cleanly from 1,000rpm in fifth, but is equally happy hunting out the red line.
And when you do get it wound up there’s all the noise, performance and excitement you could reasonably expect from the baby of the range. At times I can’t help feeling it doesn’t have the crisp sweet-revving character of the ‘K’, but nonetheless it’s a great starting point for any Caterham virgin. Especially if all the customer cars can boast a gearshift as light and smooth as our test car’s five-speeder.
Shoe-horning the Sigma engine into the Seven’s chassis was no simple matter, however. It didn’t fit. At the same time as the engine programme, the new management wanted to further refine and improve the chassis’ spaceframe design, which resulted in an end to the firm’s relationship with Arch motors – whose enginers bronze welded each chassis by hand – and an increased commitment with Caged (now Steel Fabrications Ltd) which designed and constructed all the Seven’s roll bars and race cages.
The company talks proudly of CAD modelling, FEA finite element analysis, computer controlled tube and sheet laser cutters and robotic welding cells. So the rise of the machines even touches Caterham. Whatever next -- snow in the Sahara? The question is, what does it have to show for it on the road?
On the road
I have to say, the spaceframe chassis feels a lot stiffer than the couple of Sevens I’ve run in the past. Caterham claims an increase of 12 per cent, but the impression on your backside and fingertips is far greater. The trademark flexing and creaking of the chassis is less noticeable. Which is good news, as the suspension geometry can work as it was intended to, keeping the wheels in contact with terra firma.
Driving any Caterham is usually a life-affirming experience. And I’m glad to say that’s still very much the case in the new baby of the range. There may not be a glut of power, but if you haven’t driven one in a while there’s still a whole new world of sensory stimulation that comes as a sharp wake-up call.
The test car’s Avon ZV3 tyres wouldn’t be my first choice, but there’s a lot of fun to be had trying to maintain momentum once up to speed. The DeDion chassis’ natural balance is nicely neutral. Push beyond that into understeer and you can play around with the throttle, coaxing it into gentle lift-off oversteer and then a whiff of power oversteer if you gas it again in tighter second and third gear bends. And the beauty is, with the touchy-feely tactile feedback – through the ever-wondrous steering and seat of the pants - you trust it intimately.
Criticisms? The brakes showed an unnerving willingness to lock up at the front on our car in the wet, but that’s easily fine tuned to taste. And the four-point harness really should be five, as it slips up your torso no matter how tightly you fasten the lap strap.
Meanwhile, the hood remains as quaint as ever. (Don’t slow down and you won’t get wet.)
It goes without saying that you shouldn’t approach the Roadsport 125 expecting 100mph-plus thrills, or the ability to hold court at track days. And it also goes without saying that not everyone craves the full-blown, mind-numbing performance of top-end versions.
As a starting point, then, the Roadsport 125 does all you can realistically ask of it. The Sigma’s day to day drivability is excellent, top-end performance is stirring enough and the Seven’s chassis is better than ever. And as a pointer of what to expect, it should have Caterham fans excited about the Seven’s future. Roll on the R300...
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