(continued)
A dual-scroll turbocharger with a lightweight turbine provides nearly instant
power and an air-to-air intercooling system bolsters the turbo’s performance by
reducing inlet temperatures. Dual cam phasing complements the turbocharging
system by optimizing valve timing at lower rpm for best turbo response and quick
engine torque build-up time.
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. The cylinder block bulkheads – the areas where the main bearing caps
are attached – and the bore 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.
How Direct Injection
Works
Gasoline direct injection differs from the fuel delivery process of a
conventional engine by delivering fuel directly into the combustion chamber,
where it is mixed with air drawn in to the chamber. The combustion process of
conventional fuel injected engines uses air and fuel that are mixed in the
intake port or intake manifold prior to being introduced into the combustion
chamber. Direct injection is a continuation of the evolutionary process of
moving the fuel introduction point closer to the combustion location to improve
control.
With the Ecotec 2.0-liter Turbo, fuel is introduced directly to the combustion
chamber during the intake stroke. As the piston approaches top-dead center, the
mixture is ignited by the spark plug, giving the name spark ignition direct
injection (SIDI). The fuel injectors are located beneath the intake ports. SIDI
allows the mixture to be “leaner” – less fuel, more air – at full power. SIDI
also permits a slightly higher compression ratio than if the fuel were delivered
with conventional fuel injection. The result is better fuel consumption at part
and full throttle. The engine uses conventional spark plugs similar to other
Ecotec engines.
A high-pressure, returnless fuel system is employed. 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
(155 bar) of pressure. The system regulates lower fuel pressure at idle –
approximately 752 psi (50 bar) and higher pressure at wide-open throttle. The
cam-driven high-pressure pumps works in conjunction with a conventional fuel
tank-mounted supply pump.
Direct injection’s precise fuel delivery enables more complete combustion to
help reduce emissions, particularly on cold starts – the time when most engine
emissions are typically created. Also, direct injection permits higher a
compression ratio in the engine which is a positive influence on fuel economy.
At certain power levels, the boosted SIDI engine can provide significant fuel
economy benefits to the vehicle compared to a larger displacement naturally
aspirated engine.
Turbocharging System
A unique, dual-scroll turbocharger is partnered with an air-to-air intercooling
system to provide up to approximately 20 psi (1.38 bar) of power-enhancing
boost. The dual-scroll turbocharger delivers nearly instant response, as dual
exhaust passages from the engine to the turbine housing guide exhaust gas to the
turbine. This reduces lag time, or spool-up, at low rpm.
“There is virtually no lag with this system,” said Groff. “Throttle response is
immediate. The engine acts like a larger displacement engine.”
The turbocharger is matched to the engine’s displacement and performance
objectives. It is supported by the air-to-air intercooling system, which uses
fresh air drawn through a heat exchanger to reduce the temperature of the warmer
compressed air forced through the intake system by the turbocharger. Inlet
temperature is reduced by approximately 212 degrees (100 degrees C), enhancing
performance because cooler air is denser and promotes optimal combustion.
The GXP’s high-performance Ecotec turbo engine is connected to a standard
five-speed manual gearbox, or an optional five-speed automotive transmission.
Either transmission can propel the car from zero-to 60 mph in under 5.5 seconds.
The Solstice GXP is Not Just
Another Solstice
As with other members of GXP family, the Solstice GXP provides a number of
standard features not available on the base model, including:
- Unique front and rear fascias
- High polish, dual-outlet exhaust
- StabiliTrak vehicle stability enhancement system
- 3.73 rear axle ratio
- Interior refinements including unique GXP gauge cluster and Cobalt Red
seat stitching
The GXP also comes standard with a number of features available as options on
the base model, including:
- Sport suspension system
- Four-wheel disc brakes with anti-lock
- Limited-slip rear differential
- Power window/locks/mirrors and remote keyless entry
- Leather-wrapped steering wheel with accessory controls and cruise control
- Driver information center
- 18-inch polished aluminum wheels
- Additional options include a rear deck spoiler, leather seating, sport
metallic pedals, chrome wheels, enhanced audio options, including XM Satellite
Radio, and OnStar.
The 2007 Solstice GXP will be available in fall 2006.
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