The '07 Solstice GXP will add a new dimension of performance to Pontiac's popular two-seat
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.
New rear fascia accommodates the dual exhaust outlets and gives an aggressive appearance.
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.
Perhaps the most innovative feature of the new turbocharged Solstice powerplant is the direct injection system. Essentially, the system locates the injector in the combustion chamber rather than in the intake manifold runner or intake port. This arrangement is similar in layout to a diesel powerplant, exposing the injector to the heat and pressure of the combustion event. Unlike a diesel, the Ecotec uses a conventional spark plug and otherwise operates as a normal four-cycle spark-ignition engine. The system is referred to as Spark Ignition Direct Injection (SIDI).
With fuel delivered directly to the combustion chamber to create a more complete burn of the air/fuel mixture, less fuel is required to produce the equivalent horsepower compared to a conventional port-injection system, particularly at normal cruising speeds. "Direct-injection technology works well with turbocharging and helps deliver a great balance of power and economy," says Groff. "The Ecotec 2.0-liter Turbo produces the power expected of a V-6, but in a smaller, more efficient package--and the driving response is simply terrific."
To accommodate the direct-injection system, the Ecotec 2.0-liter Turbo has a unique cylinder head and intake manifold. The cylinder head incorporates mounting locations for the fuel injectors--which are typically mounted in the intake ports or intake manifold on port injection engines. A high-pressure fuel pump delivers fuel to a variable-pressure fuel rail. Fuel enters the combustion chamber through multihole fuel injectors. The fuel pump, fuel-rail pressure, fuel-injection timing, and injection duration are controlled by the engine control module. In this way, fuel is metered and delivered in a finely atomized spray, which, during the intake stroke, is introduced into the chamber near the intake valves, in direct line of the spark plug. SIDI also permits a slightly higher compression ratio than if the fuel were delivered with conventional fuel injection and allows the mixture to be leaner at full power.
Solstice's interior is attractive, and the gauge cluster is large and easy to read.
A short shifter handle operates the Aisin five-speed manual transmission.
The rear of the Solstice GXP shows the crisp, sporty lines that have captured the interest
A high-pressure, returnless fuel system is employed for this application. It features a high-strength stainless steel fuel line that feeds a variable-pressure fuel rail. Direct injection requires higher fuel pressure than conventional fuel injected engines, and an engine-driven high-pressure fuel pump is used to supply up to 2,250 psi of pressure. This system regulates lower fuel pressure at idle--approximately 752 psi and higher pressure at wide-open throttle. The cam-driven, high-pressure pump works in conjunction with a conventional fuel tank-mounted supply pump.
Apart from the mounting positions of the fuel injectors, the cylinder head has conventional port and combustion chamber designs, although both are optimized for direct injection and high boost pressures. Sodium-filled exhaust valves and stainless steel exhaust manifold are durable components designed to stand up to the high-performance capability of the engine.
A unique cylinder head, fuel system, pistons, intake manifold, and the dual-scroll turbocharger are the only major components that differentiate the 2.0-liter Turbo from other members of the Ecotec engine family. Mobil 1 synthetic engine oil is added at the factory. Synthetic oil was selected for its friction-reducing capabilities and high-temperature performance.
Dual Cam Phasing
The camshafts of the Ecotec 2.0-liter Turbo engine have phasers that support the continu-ously variable intake and exhaust valve timing. They also have cam position sensors, so that the engine control module can accurately control valve timing. The crankshaft and camshaft position sensors are digital. A new engine controller, specific to this powerplant, is used to sense and dictate its performance parameters.
Variable intake and exhaust timing works synergistically with both the gasoline direct injection and turbocharging systems. The variable engine timing enabled by cam phasing allows the combustion process to be optimized. Also, valve "overlap" at low rpm can be adjusted by the controller to increase the response of the turbocharger, providing a more immediate feeling of power.
Solstice GXP's powerplant is a turbocharged and intercooled 2.0-liter DOHC Ecotec four-cyl
Ecotec Engine Family
The Ecotec 2.0-liter Turbo is built on a global platform that was designed at the outset for a range of performance and combustion capabilities. Gen II blocks support the high-performance demands of the engines, but are merely a strengthened version of the original Ecotec architecture. The oil pump, for example, is the same as used in all other Ecotec engines. It was originally designed to support high-performance applications of future engines.
"This 2.0-liter Turbo is the pinnacle of Ecotec performance to date, with additional growth planned," says Groff. The groundwork for its capabilities was laid on the drawing table at the beginning of the Ecotec's development. Prior work and a far-thinking engine design continue to help GM respond to market demands around the globe more quickly and with greater accuracy."
This new Ecotec family member also features:
- Dual overhead camshafts (DOHC) and four valves per cylinder
- Twin counter-rotating balance shafts for operational smoothness
- "Drive by Wire" electronic throttle control
- Low-friction, roller-finger follower valvetrain with hydraulic lash adjusters
- Low-maintenance chain-drive for the camshafts
- 58X crankshaft positioning
- Direct-mount accessories, which reduce or eliminate traditional sources of noise and vibration
- Full-circle transmission mount to reduce noise and vibration
- GM Oil Life System, which can reduce the frequency for oil changes
- Innovative cast-in oil filter housing, which eliminates the need to crawl under the vehicle to perform oil changes and eliminates throwaway oil filter cans that retain used oil
- As with other engines in the Ecotec family, the 2.0-liter Turbo engine also has premium features designed to ensure smooth and quiet operation, including a polymer coating and skirt design for the pistons that reduces noise during cold starts. An automatic hydraulic tensioner also is used to maintain optimal tension on the timing chain, which reduces noise and vibration
The Solstice Gxp Package
Though prices had not yet been announced at press time, the GXP package is expected to add between $4,000 and $5,000 to the price of a Solstice. In addition to the engine, the package will include GM's StabiliTrak four-channel electronic stability control system, as well as specific appearance items such as blacked-out grilles, GXP badging, and new front and rear fascias to accommodate the intercooler and dual exhaust outlets.
The Solstice GXP is scheduled to debut in the summer of 2006. If it does come with an MSRP in the $25,000 range, it will be a serious "bang for the buck" value, and we expect that once the hurdles of figuring out the electronics are overcome, the aftermarket will quickly gear up with a host of performance upgrades. We see no reason to think this engine would have any problem supporting over 500 streetable horsepower, which would make for an insanely fast machine that would also get great mileage--if, of course, you could keep your foot out of it.
We have been given ample evidence that GM and Pontiac-GMC have come a long way to understanding how to market an affordable two-seat performance car. It appears the bitter lessons learned by the demise of the Fiero have not been lost. With an attractively priced performance package that should deliver on all fronts, a realistic sales forecast, innovative marketing, and the potential for even more power, the Solstice GXP could well end up being one of the best performance cars Pontiac has ever released. It had better be--Pontiac and GM really cannot afford anything other than a grand slam.
Dual-scroll exhaust turbine enhances velocity, reducing turbo lag to an insignificant leve
Direct injection puts the fuel-injection nozzle right in the combustion chamber, enhancing
Additional resistance to detonation is achieved with oil spray injectors that fire oil int
|Ecotec 2.0-Liter Turbo Specifications |
|Assembly Site:||Spring Hill, Tennessee|
|Application:||'07 Pontiac Solstice GXP|
|Type:||2.0-liter DOHC turbocharged I4|
|Displacement (ci / cc):||122 / 1,998|
|Bore x Stroke (in x mm):||3.38 x 3.38 / 86 x 86|
|Block Material:||319 aluminum|
|Cylinder Head Material:||356 T6 aluminum|
|Intake Manifold:||Cast aluminum|
|Exhaust Manifolds:||Cast stainless steel|
|Valve Configuration:||Overhead cam; four valves per cylinder (35.1 mm int. / 30.1 mm exh.)|
|Valve Lifters:||Hydraulic lash adjuster, roller finger follower|
|Throttle Body:||58 mm|
|Fuel System:||Gasoline high-pressure, variable-rail pressure, spark ignition direct injection (SIDI)|
|Horsepower (hp / kW):||260 / 194 at 5,300 rpm (SAE certification pending)|
|Torque (lb-ft / Nm):||260 / 353 at 2.000-5,300 rpm (SAE certification pending)|
|Fuel Shut-Off:||6,300 rpm|
|Connecting Rods:||Forged steel|
|Additional Features:||Air-to-air intercooled dual scroll turbocharger system, variable valve timing, electronic throttle control, pressure-actuated piston cooling jets, extended-life spark plugs, extended-life coolant, GM oil level sensor, extended-life accessory drivebelt, Nimonic sodium-filled exhaust valves|
This shot of combustion chamber shows the four-valve layout, the centrally located spark p
The direct injection system is shown here with the electronic control module. It uses a re
This drawing shows the basic layout of the intercooler system. It reduces the charge tempe
Variable valve timing is used for both intake and exhaust valves. It is computer-controlle
...and uses cam position sensors for precise control. Valve overlap can be optimized in th