The 2007 Honda Civic Si Coupe is the Sport Injected (Si) version of the classic coupe version. The Si is essentially an EX trim level of the coupe with performance enhancing improvements. Honda replaces the 1.8L SOHC engine with a 2.0L K20 engine that delivers 197HP at 7800RPM.
Other improvements include a 6-speed manual transmission (no automatic option available), 17" allow wheels (up from 16"), and a helical limited-slip differential for improved handling, and a rear spoiler. Other changes are cosmetic in nature and include different coloured seat stitching and gauge back lights (red), as well as an extra Si badge.
The increased performance comes at a cost that is more than just a higher price. Fuel efficiency decreases from 30/40MPG to 23/32MPG which places the Si version in the class of Low Emission Vehicles (LEV) instead of Ultra-Low Emission Vehicles like the non-Si sibling.
A 7-speaker 300 watt stereo comes standard with the Si model with satellite navigation and XM radio being optional.