The Difference Engine: Birth of an icon



The Difference Engine: Birth of an icon

Dec 10th 2010, 9:30 by N.V. | LOS ANGELES

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PETROL-HEADS of a certain age may have noticed that the 50th anniversary of the Jaguar E-Type sportscar is imminent. Within the motoring world, it will be the cause for much ballyhoo and dewy-eyed nostalgia. But before getting caught up in all the hoopla, your correspondent—wizened enough to have been around when the iconic car made its debut at the Geneva motor show in 1961—would like to contribute his two-pennyworth of personal experience on why the E-Type really was the most innovative piece of automotive machinery of its age. 

The most extraordinary thing about the E-Type was not just that its wind-cheating aerodynamic shape—at least in fixed-head coupé form—endowed it with one of the lowest drag coefficients for a mass-produced car ever. Nor was it simply the fact that the novel independent suspension at the rear, as well as at the front, allowed it to skate round corners like nothing before, while disc-brakes on all four wheels could bring it so abruptly to a stop. Nor even was it the powerful twin-cam engine, with its racing heritage, that could propel the car to 150 miles per hour in an age when the fastest most cars could manage was little more than half as much. 

All those features, and more, would have been enough to make the E-Type a classic. But what turned it into an icon that has endured for 50 years was the simple, yet remarkable, fact that it cost only half as much as anything comparable. In short, it put extraordinary motoring within the grasp of ordinary people.

As legend has it, Jaguar founder William Lyons (later knighted) and three key engineers, William Heynes, Walter Hassan and Claude Baily, used to discuss future engine designs while performing their nightly fire-watching duties from their factory rooftop during the latter years of the Second World War. When dawn came, they would trot downstairs to build prototypes that incorporated every conceivable innovation in engine design known at the time. 

The final result of all the talking and tinkering was a freely breathing, lightly stressed six-cylinder engine of 3.4 litres displacement, with a rigid cast-iron block and an aluminium cylinder head (better for dissipating heat) that incorporated opposed valves in hemispherical combustion chambers, driven by twin overhead camshafts. When the so-called XJ6 engine went into production in 1947, for the forthcoming XK120 sportscar, it was so ahead of its time that it would go on to power practically every Jaguar made for the next 40 years—not to mention the company’s legendary C-Type and D-Type racing cars that overwhelmed the annual Le Mans 24-hour endurance race during the 1950s. 

From the start, the layout of the XJ6 engine was so inherently correct that the only way it could be improved was to increase the cylinder diameter. Even then, enough room had been engineered into the block to allow for this to happen. To provide still more power, the engine would eventually be bored out first to 3.8 litres and subsequently to 4.2 litres. Even 20 years after its introduction, Mercedes, BMW and other makers of straight-six engines struggled to match the XJ6’s torque, refinement and reliability.

Thus, when the E-Type was being planned, Jaguar did not have to develop a powerful new engine. Nor did it have to invest in tooling to make it. The same could be said for the modern disc-brakes that are taken for granted nowadays. These were introduced to the world on the C-Type in 1952 for the Mille Miglia race in Italy, where sceptical officials, never having seen such things, demanded a demonstration before allowing the car to compete. By 1958, Jaguar had fitted fade-free disc-brakes as standard to the XK150 sportscar, the E-Type’s predecessor.  

The money saved from not having to develop a powerful new engine nor an advanced braking system was devoted instead to other innovations—most notably, the E-Type’s aerodynamics, unitary body construction and, above all, its revolutionary independent rear suspension. Even then, much of the engineering had been tried and tested on the D-Type racer. This way the E-Type’s development costs were kept to a minimum, making the final price of the car (around £2,100 after tax) half that of a comparable Aston Martin.

No account of the E-Type would be complete without mention of Malcolm Sayer, one of the first engineers in the world to systematically apply aerodynamic principles to car design. A firm believer in the use of wind tunnels and smoke testing, his first creation at Jaguar was the streamlined C-Type followed by the even more radical D-Type. The latter’s light but stiff monocoque body carried the various loads through its outer structure like an aircraft fuselage, rather than via a heavy frame-like chassis, as the C-Type and other cars had largely done till then. 

For the road-going E-Type, Sayer took a lengthened version of the monocoque concept with a subframe to brace the front torsion-bar suspension, but added an entirely new type of rear suspension. Given its power-to-weight ratio, a solid rear axle would have made the E-Type more than a handful for the average motorist, as the back end hopped and skipped under hard acceleration. The only answer was to make the motions of the rear wheels independent of one another. 

In Sayer’s design, each wheel had its own a pair of springs, one on either side of the drive shaft, with the disc brakes placed well inboard—so they would not add to the unsprung weight of the rear wheels and thereby hamper the action of the springs and shock absorbers. The assembly was carried on a pair of steel cross-members, which were bolted to the monocoque underbody by means of four large rubberised mounting pads. The arrangement not only improved the ride and handling of the car, but also isolated the interior from most of the noise and vibration generated by the wheels, suspension and the differential.

When Enzo Ferrari clapped eyes on the E-Type for the first time, he declared it “the most beautiful car ever built”—and went on to copy aspects of it for various Ferrari models that followed. But it wasn’t just Sayer’s flowing lines that captivated the Italian master carmaker. The E-Type’s innovative rear suspension subsequently found its way, in one form or another, into luxury and performance cars the world over. 

With the E-Type, Sayer created not just a motoring icon, but a whole design language that shaped the thinking of generations of car designers thereafter. If you look carefully, you can see how the long bonnet, feline curves and haunches over the rear wheels that defined the E-Type’s stance on the road have become features of practically every Jaguar since. Even today, when so much of a car’s external shape is governed by strict regulations that determine the height and position of every fitting, the DNA inherited from Sayer’s E-Type continues to infuse even the latest Jaguars developed under Ian Callum.

Over the years, your correspondent has driven a number of E-Types. His favourite, by far, remains the later 4.2-litre version of the Series 1 model in coupé form. By today’s standards, the E-Type is not particularly fast nor forgiving. But all versions have such stunning looks and purity of character as to mark them as truly great machines. Your correspondent never owned one. He wished he had.

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