The 2.4L also shares Ecotec family traits that have helped forge a reputation for durability and sophistication:

• Dual overhead camshafts (DOHC) and four valves per cylinder

• Twin counter-rotating balance shafts for operational smoothness

• 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

• Catalytic converter located close to exhaust manifold to speed catalyst "light off," reducing hydrocarbon emissions

The camshafts of the 2.4L engine have phasers that support the continuously variable intake and exhaust valve timing. They also have cam position sensors, so that the electronic control module can accurately control valve timing. The crankshaft and camshaft position sensors on the 2.4L engine are digital.

The 2.4L 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; it maintains optimal tension on the timing chain, which reduces noise and vibration.



Transmissions

An Aisin five-speed manual transmission is standard on the Solstice. It features a 3.75:1 first gear, along with closely stepped higher gears that help keep the engine at the sweet spot in its power band during shifts. This contributes to a sportier driving feel and extracts maximum performance from the 2.4L Ecotec engine. Shifter feel and throw length is optimized to deliver short, precise shifts. First and second gears feature triple-cone synchronizers for a smoother shift feel.

Later in the '06 model year, the advanced Hydra-Matic 5L40-E five-speed automatic transmission will be offered as an option. As with the five-speed manual, the gear steps of the automatic complement the horsepower and torque bands of the engine.

The transmissions channel torque to an independent rearend that features a 3.91:1 axle ratio. The gears are housed in a rear axle derived from the Cadillac CTS, which was chosen for its excellent performance characteristics and high torque capability. A limited-slip rear differential is available. It uses a pre-loaded, friction clutch-type design and divides power equally between both rear wheels during normal driving conditions, but in low-traction conditions, the differential transfer torque to the wheel with better grip.

*Preliminary, pending certification. A new voluntary power and torque certification procedure developed by the SAE Engine Test Code committee was approved March 31, 2005 . This procedure (J2723) ensures fair, accurate ratings for horsepower and torque by allowing manufacturers to certify their engines through third-party witness testing. GM was the first auto manufacturer to begin using the procedure and expects to use it for all newly rated engines in the future.

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