The ION is available as a four-door sedan or an innovative coupe, which Saturn calls a Quad Coupe for its unique reverse-opening rear doors. The base engine for the ION is a 2.2-liter four-cylinder rated at 145 horsepower. Also available is a 2.4-liter four-cylinder rated 175 horsepower. The top-performing Red Line model on the coupe only, comes with a supercharged 2.0-liter four rated 205 horsepower. A five-speed manual transmission is standard, and a four-speed automatic transmission is optional. The sedan is offered in two trim levels: the ION 2 and the ION 3. Quad Coupes come in the ION 2, the ION 3, and the Red Line trim.For 2007, the Saturn ION 2 and the ION 3 receive an engine horsepower increase.