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GM, keen to steal back some of Toyota's thunder by offering hybrid petrol-electric models, has launched two hybrids at the Detroit Motor Show - the Saturn Vue Green Line and the Chevrolet Tahoe.
The Vue, positioned in GM's high-value Saturn line-up, is said to deliver a 20% improvement in fuel economy compared to its conventional counterpart: that's 27mpg in the city and 32mpg on the highway, which may not be super-frugal, but better than most similarly-sized gas-guzzling SUVs. The premium for the hybrid will be less than $2,000, with prices starting from $23,000; it's estimated that this extra outlay will be outweighed by savings on fuel after about 60,000 miles.
A fairly traditional SUV on all other counts, the Vue Green Line has a 2.4-litre four-cylinder petrol engine with four-speed automatic transmission. It's a so-called mild hybrid, with the electric motor assisting the petrol engine under acceleration. The engine also shuts down at idling and automatically restarts, and cuts off fuel supply under deceleration, but the motor cannot power the vehicle alone in a fully-electric mode. This system does, however, have the advantage of being relatively simple and cheap to produce.
The Vue Green Line goes on sale in summer 2006, as one of the first of 12 hybrids GM is planning for the near future.
To go on sale next year is the larger Chevrolet Tahoe hybrid, revealed in Detroit alongside the Vue. The Tahoe hybrid, and its sister GMC Yukon models, is a full hybrid with two-mode operation. Improvements in fuel economy of 25% are claimed and it can run in fully-electric mode at city speeds for extended periods of time. At low speeds, it can operate with some of its eight cylinders deactivated, but at highway speeds, it can then utilise all capacity for optimum performance.
This patented system, developed in a partnership between GM, DaimlerChrysler and BMW, from technology used in GM's hybrid buses, is compact enough to fit in conjunction with a conventional automatic transmission, rather than the CVT gearboxes Toyota uses. The 300-volt battery pack is packaged so it does not eat into passenger space and it can be automatically charged from the engine. GM expects to use this flexible system in a variety of different types of vehicle, and it can even be adapted for use with a diesel engine, potentially offering the best fuel savings of all.
The hybrid Tahoe has a few minor modifications from the standard-issue model: it has been lowered by 10mm for improved aerodynamics, its bonnet and tailgate are made from aluminium to save weight and its bonnet is more streamlined. It also has larger air intakes in its grille and more aerodynamic side running boards and trim around its corners, D-pillars, taillights, rear spoiler and air dams, plus lightweight wheels with low rolling-resistance tyres - all of which go a long way to achieving that 25% improvement even before the electric motors are fitted.
A similar dual-mode hybrid system is expected to feature in the Cadillac Escalade range shortly. However, this "full" hybrid technology is likely to be somewhat more expensive than the system used in the Saturn Vue.
