The 2007 Honda Civic comes as six distinct models: sedan, coupe, Si sedan, Si coupe, Hybrid sedan, and natural-gas GX sedan. The sedan and coupe both have a 1.8L i-VTEC four-cylinder engine, making 140 horsepower and 128 lb-ft of torque. A five-speed manual is standard. The sedan and coupe meet ULEV-II emissions standard in all 50 states. The Si Sedan and Coupe step up to an especially high-revving 2.0L i-VTEC four-cylinder engine making 197 horsepower and 139 lb-ft of torque, paired with a six-speed manual transmission and employing a helical-type limited-slip differential to help ensure smoother power delivery in high-performance driving. The Si models also get significant upgrades, including 17-inch wheels and high-performance V-rated tires, special trim and bolstered sport seats with red stitching inside, and a rear wing and aerodynamic cladding outside. All Civics have Honda's Advanced Compatibility Engineering (ACE) body structure, which helps more evenly absorb the force of frontal collisions and also helps in collisions with vehicles of differing sizes. Four-channel anti-lock brakes with electronic brakeforce distribution, front occupant side air bags, two-row side-curtain air bags, active front head restraints, and rear head restraints for all positions are standard on all models, too. The Civic Hybrid only comes as a sedan. It brings a smaller 1.3L four-cylinder engine paired with a 20-horsepower electric motor as part of Honda's Integrated Motor Assist hybrid system, in which the electric motor boosts the gasoline engine when accelerating, saves some of the energy lost in braking, and allows the engine to turn off at stoplights, provided your foot is on the brake. Together, the engine and motor deliver 110 horsepower and 123 lb-ft of torque. Finally, there's the Civic GX, which is also only available as a sedan and is powered exclusively by natural gas. The GX is only available at select dealerships in California and New York, and comes with a 113-horsepower, 1.8L four-cylinder engine. Sedans and coupes (except the Hybrid and GX) are available in three trim levels: the frugal DX, the well-equipped LX, and the more luxuriously appointed EX. The DX gets power windows and locks and tilt/telescope steering, among other basics. The LX adds popular features like air conditioning, cruise control, remote entry, and a CD sound system, while the EX brings extras like a six-speaker sound system that's XM ready and a 60/40-split folding rear seat to make the trunk area more versatile. Si models are equipped with a similar level of conveniences as EX models, but they also get a 350-watt, seven-speaker sound system with a subwoofer. A satellite-linked navigation system with voice recognition is optional on EX and Si models and has a 6.5-inch display screen. The system also brings a CompactFlash card reader, so that MP3 or WMA media can be played on the sound system.