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Tuesday, January 20, 2009

The Low Down on Jaguar's New Engines

Jaguar chose Detroit to unveil its new direct-injected 5.0-liter V-8 engines that will power its XK coupe and XF saloons, including the super-quick R models that pitch the marque against BMW's M-cars, the AMG models from Mercedes and Audi's S offerings.

The supercharged version puts out 503 bhp at 6000–6500 rpm, while the normally aspirated V-8 produces 380 bhp at 6500 rpm. But the really impressive figures are for torque delivery — a mammoth 461 lb.-ft. on tap from 2500 to 5500 rpm in the blown variant, and a no-less-impressive 380 lb.-ft. at 3500 rpm for the non-supercharged engine.

Clever use of variable cam timing, the same Borg-Warner system Ford employs on its new 3.0-liter V-6, cam-profile switching (except on the blown engine) and a variable inlet manifold mean the XKR now hits 60 mph in 4.6 seconds while returning 23 mpg. The new XFR is just a tenth slower to 60 and returns 22.5 mpg.

Although development of the engine started when Jaguar was still with Ford, Jaguar programe director, Mick Mahon, was at pains to emphasize that the power units were designed and developed in-house at Jaguar's Whitely engineering center.

The all-new aluminium-block engines share just two components with the old 4.2, which continues to be available in the U.S.: cylinder head bolts and tappet buckets, that's it.

In addition to the huge gains in torque and power over the previous-generation V-8s, the distinctive supercharger whine has been eliminated, says Mahon, thanks to a unique sound resonator that amplifies the V8's distinctive engine note under hard acceleration. The first time this technology has been used on a supercharged engine.

But, perhaps, the most noticeable 'first' for Jaguar with the new engine is the centrally mounted injector with the valves surrounding it, ensuring an optimized spray pattern for maximized air-fuel mixing and minimal cylinder wall wetting.

"We're in the midst of rebuilding Jaguar," enthused managing director, Mike O'Driscoll, "and these new engines put the fast into beautiful, fast Jaguars."