X-Type: from four- to two-wheel drive

Visually the 2.0-L Jaguar X-Type is virtually identical to larger engined versions.

Four-wheel-drive versions of a model range may be introduced after the two-wheel-drive version has become established, but Jaguar went about things differently. When the transverse-engined X-Type appeared last year with four-wheel drive (and a choice of 2.5- or 3.0-L AJV6 engines), there was conjecture that a front-wheel-drive only version would be produced. That has proved to be the case, with the introduction of the X-Type 2.0-L and front-wheel drive. It is the first front-wheel-drive Jaguar—a layout that may be anathema to some Jaguar purists, but which is likely to prove a popular application.

The company has reduced the capacity of the all-aluminum AJV6 to 2.1-L, although for marketing reasons, the model has been officially designated 2.0-L. All X-Type engines are based on the 3.0-L V6 unit of the S-Type, which itself is based on Ford technology, albeit with extensive changes. Power output of the 2.0-L is 117 kW (157 hp) at 6800 rpm, with a peak torque of 200 N•m (148 lb•ft) achieved at 4100 rpm. The smaller unit is almost identical to the 2.5-L V6, except for a shorter stroke of 66.8 mm (2.6 in) compared to 79.5 mm (3.1 in). It has two overhead chain-driven cast iron camshafts per cylinder bank, four valves per cylinder, and a four-mode, variable geometry intake manifold. The AJV6 also has continuously variable intake cam phasing, which enhances mid-range torque, improves full-load performance, and reduces emissions, says Jaguar. The engine drives through the same five-speed Getrag manual transmission as that fitted to the larger-engined X-Types, with a five-speed auto as an option.

The X-Type 2.0-L V6 engine is technically a 2.1-L unit.

Jaguar said the 2.0-L's engineering program focused on steering precision and feel, a traditional weakness of front-wheel-drive cars, according to Jaguar. The rack-and-pinion steering is similar to that of the all-wheel-drive models. "But program engineers undertook Taguchi-based design of experiments, using complex simulations to understand fully the mechanisms of steering under power. The work led to several key design features, including equal-length and -stiffness half shafts; geometry calculated to ensure that the half shafts are perfectly aligned under torque; special constant velocity joints at the outboard ends of the half shafts to reduce friction; and, as fitted to the 2.5- and 3.0-L cars, a specially designed strut top mount to eliminate strut friction under torque. A ZF variable ratio steering system is used with an on-center ratio of 16.8:1, rising to a maximum 9:1 on lock. An inner bearing is used to counter the torque-steer effect. The bearing allows the strut piston to rotate freely even under the effects of engine torque, says Jaguar.

Jaguar's chassis focus was on steering precision and feel for the front-wheel-drive X-Type.

A specific piston and shim stack within each damper has been developed for the 2.0-L to tailor body control and handling characteristics. Electronic traction control is fitted, and dynamic stability control (DSC) is an option. Performance figures include a 0-100 km/h (62 mph) time of 9.4 s and a top speed of 210 km/h (130 mph).

- Stuart Birch

Twin turbos for Bentley Arnage

Bentley's new 6.75-L Arnage, now with twin turbochargers, is designated the Arnage T and claimed to be the fastest production sedan in the world.

Bentley claims its twin-turbo Arnage T as the world's fastest production sedan, with a top speed of 270 km/h (168 mph). That may be disputed by companies who voluntarily put a 250-km/h (155 mph) electronically controlled limit on their products, but for a car with a mass of 2585 kg (5700 lb), its performance is brisk. Numbers include a 0-97 km/h (60 mph) time of 5.5 s, 0-160 km/h (100 mph) in 13.5 s, and 80-112 km/h (50-70 mph) in 3 s. Since Bentley became part of the Volkswagen Group, the Arnage range has been thoroughly re-engineered. Although the T model looks similar to the original Arnage, Bentley says that "not a single significant area of its design has been left untouched," and that it is virtually a new car.

The major element of work has centered on the extensively modified 6.75-L V8 engine. Producing 336 kW (450 hp), it is more powerful than any previous Bentley power unit. The change from single to twin turbos has also brought greater torque—875 N•m (645 lb•ft) at 3250 rpm—and emissions benefits, made possible by the fitment of close-coupled catalytic converters near the exhaust manifold. Bosch Motronic ME7 engine management is fitted, and the block has modified water jackets. The pistons have been changed and have a revised crown configuration and their recesses removed. Camshaft design features increased lift and duration characteristics plus stronger push rods. The cylinder heads have been completely redesigned to accommodate new and lighter valves with stiffer rocker pedestals, while great attention has been paid to gas flow around the heads to improve volumetric and thermal efficiency. Over 50% of the engine has been changed and 80% re-engineered. A drive-by-wire throttle is fitted.

An extensively re-engineered 6.75-L 336-kW (450-hp) engine powers Bentley's Arnage T.

Other changes that mark out the Arnage T include enhanced torsional rigidity, computer-controlled sports suspension, and the addition of a rear anti-roll bar. The car has ESP (Electronic Stability Control).

- Stuart Birch

Opel's concept monocab

Opel's Concept M, revealed at the Geneva Motor Show, is set to mature into a production model next year.

The Opel monocab Concept M design study, which made its world premiere at the Geneva Motor Show in March, has a natural-gas-powered, turbocharged, 110-kW (148-hp), 1.6-L engine and Easytronic automated manual transmission. Opel's concepts often lead directly or indirectly to production models, and the Concept M, based on a stretched Corsa platform, is expected to reach production next year. It has design links with the new Opel Vectra and the company's Signum2 concept seen last year, and is 4.05 m (159.4 in) long and 1.78 m (70 in) wide. It has four seats, but the production car is likely to have five with versatile configurations. The Concept M has a roof-mounted console with DVD system and features a personal digital assistant with Internet access. Whether the gas-powered engine would be offered in a production version of Concept M is not clear; more likely it would be the company's established 1.6- and 1.8-L gasoline engines, together with a 1.7-L turbodiesel.

- Stuart Birch