2007 Pontiac Solstice GXP - A Serious Boost In Performance

Pontiac's debut of the long-awaited '06 Solstice was a high-profile, Donald Trump-fueled introduction that pretty much forced the American car-buying public to take notice that General Motors was reinventing its ailing performance division, which was suffering from obsolete product, low R&D budgets, and lackluster marketing campaigns. The fact that the Solstice was featured on The Apprentice certainly did not make it a great car, but the innovative marketing campaign did a good job of getting the word out that Detroit is making some exciting products worthy of consideration in the import-dominated market. It remains one of the few domestic offerings whose demand outstrips the supply of available units.

Likewise, the automotive media has given the Solstice some of the highest praise any American car has received in recent memory. Granted, the perception is that the car is not quite up to the Japanese in terms of such subjective categories as "refinement" and "feel." And, of course, the interior materials are always criticized in any domestic offering. It is remarkable, though, that the first time out, the Solstice was actually considered to be in the same ballpark as the Mazda Miata, which has been in production since 1990. Not too bad a showing for the car company some think cannot get anything right.

For the '07 model year, Pontiac has seriously upped the ante in performance for the Solstice, in the form of the Solstice GXP, which debuted at the '06 Los Angeles International Auto Show. It features a turbocharged, intercooled, and direct-injected version of the familiar Ecotec four-cylinder, the first such application in a North American GM offering. This engine is tentatively rated at 260 hp at 5,300 and 260 lb-ft of torque, available from 2,000 to 5,300 rpm. This makes it GM's highest specific-output engine ever, at 2.1 hp per cubic inch of displacement (130 hp / 97 kW per liter), and the most powerful production engine in the Ecotec family. It is a high-tech wonder and really shows just how far engine development has evolved in the last several years.

Improving An Already Sturdy Design
A lot of development work went into this new version of the Ecotec; it wasn't simply a matter of plunking a turbo on the engine. Indeed, every major casting was redesigned to provide a heightened level of reliability, though the engine was originally designed for use in forced-induction applications.

As with the new supercharged Northstar engine in the new Cadillac XLR, the displacement of the Solstice GXP's is slightly smaller than the normally aspirated version. Both feature a reduced bore size to increase cylinder-wall thickness. The Ecotec Turbo's stroke is also reduced and features a beefy, forged-steel crankshaft for additional durability. Bore and stroke are 86x86 mm (3.38x3.38 inches) for a total displacement of 1,998 cc's or 122 ci.

The Ecotec 2.0-liter Turbo uses a stronger, "Gen II" Ecotec engine block, which was developed with input from racing experience to support increased horsepower and torque. Cylinder-block bulkheads--the areas where the main bearing caps are attached--and the cylinder walls are enlarged for strength. Other areas of the engine were enhanced to reinforce the structure, and the water jacket is deeper for added cooling capacity and improved cylinder-bore roundness. This architecture is shared with the 2.4-liter Ecotec engine that debuted in the Pontiac Solstice roadster.

Its bottom end is also upgraded to handle the additional boost. In addition to the forged-steel crankshaft, the Ecotec Turbo also employs forged connecting rods and cast pistons. The pistons feature a dish shape that deflects injected fuel toward the spark plugs. They are cooled with a jet-spray of oil on their undersides that directs the oil into a cast-in channel inside the piston, further resisting detonation.

Additionally, the Ecotec 2.0-liter Turbo four benefits from variable valve timing and an intercooled, twin-scroll turbocharger system to provide boost. A dual-scroll design is used on the exhaust turbine and speeds up velocity and response, much in the same way a two-plane intake manifold performs the identical function. The result is a nearly lag-free system, one that gives the 2.0-liter four the feel of a much larger engine. Dual cam phasing complements the turbocharging by optimizing valve timing at lower rpm for best turbo response and quick engine torque build-up time. "There is virtually no lag with this system," says Ed Groff, assistant chief engineer, Ecotec 2.0-liter Turbo engine. "Throttle response is immediate. The engine acts like it has a larger displacement engine."

Its turbocharger provides up to approximately 20 pounds of boost. It is matched to the engine's displacement and performance objectives, and is supported by the air-to-air intercooling system, which reduces inlet temperature of the turbo-compressed air by approximately 212 degrees (100 degrees C), enhancing performance because cooler air is denser.