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V-8 rumble returns to Pontiac Grand Prix

February 11, 2005|by MALCOLM GUNN/Wheelbase Communications

The Grand Prix has always been considered the extrovert in the Pontiac family. With the arrival of the new GXP model, the car's outgoing nature comes with the added bite of a V-8 engine.

That particularly distinctive sound hasn't been heard from a Grand Prix in nearly 20 years. The V-6 revolution of the 1980s and '90s muted both the power and the octave range of the Grand Prix, or at least it seemed that way.

But in a surprising but most welcome move, Pontiac is restoring the power, and hopefully the glory, to its 43-year-old name. When it arrives in showrooms this spring, the V-8 GXP will join the 200-horsepower 3.8-liter, V-6 GT and supercharged 260-horsepower GTP variants of the Grand Prix lineup.

It seems the idea for upping the cylinder ante originated with the Bonneville, the Grand Prix's bigger brother that introduced its own GXP series in 2004. Fully 30 percent of buyers, intrigued by the idea of a 4.6-liter Cadillac-based V-8 stuffed between the Bonneville's flanks, opted for the GXP despite the $6,000 it commanded over the mid-grade SLE.

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Cadillac's 275-horse DOHC Northstar motor won't be inserted into the Grand Prix GXP. Instead, a 5.3-liter V-8, code-named the LS4, originally designed for rear-wheel-drive applications, has been selected for duty in this front-driver. Producing 303 horsepower, the 5.3 delivers more output than the Bonneville GXP's engine and also overwhelms the supercharged GTP that was, until now, the leader of the Grand Prix pack. And, in case you were wondering, the LS4 delivers significantly more torque.

To "transversely" fit the V-8 sideways into the Grand Prix GXP, Pontiac engineers came up with a shorter crankshaft to reduce engine length and devised a more compact single-belt accessory drive.

A four-speed automatic transmission with steering-wheel-mounted manual gear selection completes the powertrain.

To try to curb the LS4's appetite for premium unleaded fuel, the engine is the recipient of displacement-on-demand technology. Under low-load conditions such as idling or freeway cruising, half of the cylinders are electronically deactivated, effectively turning the V-8 into a four-cylinder. Full power is instantly and seamlessly returned when the accelerator pedal is pushed. Pontiac claims a gain of up to 12 percent in overall fuel economy with this system.

V-8 power is just part of the GXP package, although it's admittedly the biggest draw. It sits a little lower and the suspension has been beefed up with gas-charged struts, stiffer springs and a larger rear anti-sway bar. In addition, there are larger-diameter brake rotors for added stopping leverage.

The GXP rides on 18-inch rubber, with the front tires slightly wider than the rears in an attempt to improve steering control.

Grand Prix spotters will note a distinctive front and rear fascia plus additional side trim that distinguishes the GXP from its more run-of-the-mill siblings. The interior also gets some special treatment with suede inserts covering the seats and brushed-aluminum trim pieces in evidence on the control panel and door sills.

In terms of overall output, the 3,600-pound Grand Prix GXP weighs around the same as the GTP but roughly 200 pounds less than the bigger Bonneville GXP. Combined with the superior thrust emanating from the LS4, the Grand Prix should return to its rightful perch atop Pontiac's four-door performance pecking order.

The division also appears to be actively stealing a page from the playbook of other North American and foreign-based automakers, including BMW, Mercedes-Benz and Cadillac by creating high-output, well-equipped versions within its sedan fleet. It's a concept that worked well more than four decades ago with the arrival of the first Grand Prix and should catch fire again with this latest edition.

Copyright 2005, Wheelbase Communications

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