As the automotive world counts down to the New York auto show this week, Pontiac has released a preview of the 2009 Pontiac G8 GXP muscle sedan. Marking a significant gain in performance, the GXP produces Corvette-grade 402 horsepower from an 6.2-liter LS3 V-8. Preliminary performance figures from Pontiac show the GXP is capable of running 0-60 mph in about 4.7 seconds, continuing through the quarter-mile in 13.0 seconds at 108 mph.
The secret to the prodigious power output? This engine features a revised, larger-bore cylinder block, high-flow, L92-style cylinder heads; larger-diameter pistons; unique camshaft and camshaft timing; revised valvetrain with offset intake rocker arms; high-flow intake manifold; and high-flow fuel injectors. The LS3 engine has an aluminum cylinder block with cast-in-place iron cylinder liners. Larger bores help create a 376-cubic-inch displacement. The block casting also features revisions and machining in the bulkheads to enhance its strength and improve bay-to-bay breathing. New pistons were designed for high-rpm performance.
New, high-flow cylinder heads aid engine breathing and are based on the large port and valve design found on the LS7 engine and other GM L76 engines. The larger-capacity, straighter intake port-design optimizes intake flow to the combustion chamber, an effect augmented by large valves, measuring 2.16 inches (55.0 mm) on the intake side and 1.59 inches (40.4 mm) on the exhaust side.
The engine comes matched with a six-speed 6L80 automatic transmission, with a generous 6.04:1 overall ratio that enables a “steep” first-gear. The result is strong launch acceleration along with “tall” overdrive ratios that lower engine rpms for better fuel economy and reduced noise. A new six-speed Tremec TR6060 manual transmission is optional – a rare, and expensive, move for the manufacturer for the limited, expected take rate. A 3.27 final drive ratio comes with automatic-equipped GXPs, and a 3.70 gear is matched with the manual transmission. A limited-slip differential is standard.
To help keep the performance in check, the GXP features a Brembo braking system with 14-inch vented front and 12.76-inch rear disc rotors, with special quad-piston alloy calipers in front. The alloy calipers on the rear brakes have single-piston actuation. At each corner is a 19-inch polished aluminum wheel wrapped with summer 245/40R19 tire are standard. Comparable all-season tires are available.
To set the GXP off, it features a unique front fascia with a lower splitter and a distinctive rear fascia diffuser. Inside, the GXP has two-tone, heated sport seats with color-coordinated gauge cluster and GXP embroidery, plus the usual array of power amenities and leather trim bits.
All told, the GXP promises to be a powerful, refined sport sedan. Pricing hasn’t been announced, or hinted at, but it does go on sale in the 2009 calendar year. Needless to say, with the muscle car resurgence, the next year should be quite entertaining indeed.
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