Jaguar D-Type Design
However, in a way characteristic of the often-shifting logic behind Jaguar model nomenclature, the new racer became known as the D-Type even before its chassis numbers were given the suggestive prefix XKD. But the "D" might easily have stood for "departure," because in many ways, that's just what the D-Type was.
©2007 Jaguar Cars and Wieck Media Services, Inc.
The Jaguar D-Type was wider and lower than the
C-Type and at 1,930 pounds, 10 percent lighter.
Certainly, basic layout and much hardware were carried over from the C-Type. An XK six-cylinder engine still resided in front and drove through a four-speed gearbox to a live rear axle. Front suspension remained independent, and there were all-round torsion bars and telescopic dampers.
Front radiator, rear rubber-bag fuel tanks and spare tire, rack-and-pinion steering, disc brakes and lift-up nosepiece were all familiar, well-tested competition concepts.
But the engine had a dry-sump lubrication system, adopted partly to cure the oil-surge problems sometimes experienced with C-Types and partly to reduce the engine's height.
Also equipped with a smaller flywheel and three-plate clutch, the revised powerplant mounted nearly three inches lower, which not only allowed a lower hoodline for minimizing drag but also lowered the center of gravity for consequently improved stability. To make room for the trio of Weber carburetors in a physically smaller car, the entire engine was tilted eight degrees to port.
Output was now 250 horsepower at 6,000 rpm, according to documentation released on the car's announcement, though subsequent information downgraded that by 5 or 10 horses and 200-300 rpm. But more powerful the D-Type engine definitely was, thanks to 9.0:1 pistons, new cam timing, larger intake valves, and a more aggressively tuned exhaust system. Torque came to 242 pounds/feet at 4000 rpm.
Continuing the departures was a completely new gearbox with bottom-gear synchromesh for the first time. Rear suspension was modified to provide more positive axle location, and much of the front suspension hardware was new, with that elegant, satisfying look of purpose-built forgings.
The wheels, no longer the familiar old wire-spoke affairs, were a stronger, lighter disc design by Dunlop.
Strong and light aptly described the D-Type's new chassis. Its middle part, where the driver and theoretical passenger sat, was a "tub," a monocoque structure made of folded, riveted and arc-welded light alloy. Jaguar's monocoque was not quite the first-ever application of this aircraft construction technique to auto racing, but it was the-first of significance.
Adding strength to the central spine of the monocoque and completing the chassis forward of the firewall was a space-frame mainly made up from square-section tubes. These were made of aluminum and welded directly to the tub. Gracefully shrink-wrapped around all this lightness was a new bodyshell, the result of much wind-tunnel research by Malcolm Sayer.
Dimensionally, the D was distinctly more diminutive than the C. Its wheelbase was more than five inches shorter, at 90.6. Its front track, at 50 inches, was one inch narrower, and the rear was three narrower, at 48. Turning circle was a foot less, at 32.
Nose to tail, the D-Type body initially measured 154 inches (versus 157), though later it would grow a little longer. From the start the D was a trifle wider, its aerodynamic fenders swelling to 65.4 inches, though that was just 1.9 inches up on the C's maximum width, which was established by its protruding wheel nuts.
But the new car was lower through the body and, in original form, had a windshield for the driver alone, so frontal area was only 12.5 square feet, a useful 9.4-percent reduction from the C's 13.8 square feet.
Drag, which Jaguar measured as horsepower required to maintain 100 mph, was down more than 28 percent (38 horsepower versus 53). Even against the "droop snoot" C, the D-Type was cleaner by 4 horsepower, or almost 10 percent.
The extra slipperiness was apparent on the Mulsanne Straight, where the 1954 D clocked nearly 174 mph, some 14 percent faster than the unstable 1952 car.
As always, numbers for weight are suspect, but a D-Type figure used by the factory itself was 1,930 pounds, about 10 percent less than the C-Type. Distribution was 1,000 front/930 rear, or 51.8/48.2 percent. This was in "dry" condition, of course.
Aerodynamic testing figures published by Jaguar's Bob Berry in Jaguar: Motor Racing and the Manufacturer show a presumably race-condition weight distribution even more nose-heavy, 53.5/46.5. Yet at a speed not specified, but probably 100 mph, this reduced to 51/49. That meant the new car was not only faster than the ill-fated "droop-snoot," it was far more stable, actually gaining effective weight on the back end.
The whole car may have been lifting, but at least the tail wasn't lifting more than the nose. And once a prominent fin was added to the headrest, D-Type drivers reported they could scream along at 170-plus with their hands off the steering wheel. It was restful, they said.
For more on Jaguar and other great cars, see:
- Jaguar Cars: Check out more information on the great sporting cars.
- How Sports Cars Work: Get the lowdown on hundreds of fantastic sports cars from the 1940s to today.
- Classic Cars: Learn about the world's most coveted automobiles in these illustrated profiles.
- Ferrari: Learn about every significant Ferrari road car and racing car.
- New Jaguars: Reviews, ratings, prices, and specifications on the current Jaguar lineup from the auto editors of Consumer Guide.
- Used Jaguars: Reviews, recalls, trouble spots, and more on pre-owned Jaguars starting with the 1990 model year. From the auto editors of Consumer Guide.