Saturn has improved the Ion each year since its introduction as a 2003 model. The steering is much better, thanks to recalibrated steering, though it still seems sensitive at high speeds. The variable-ratio steering is electrically assisted, a technology General Motors developed first for its luxury cars. It makes the steering boost more effective at slow speed and improves fuel economy as power is not sapped from the engine by a hydraulic pump. The downside is that there is little feedback through the wheel, making it difficult to know how much traction the front tires have in cornering. We do like the sedan's small turning radius, which is a couple of feet tighter than that of a Dodge Neon or Ford Focus. That's useful when making U-turns.

Ride and handling are about average for the class. The Ion seems to be free of squeaks and rattles, especially since additional sound deadening material was added for '05. GM's Quiet Steel is used in the firewall between the engine compartment and passenger area. (Two pieces of steel sandwich a layer of asphalt, which absorbs vibration much better than traditional materials.) A noise-absorbing cover over the engine cuts sound from that source. Overall, the latest Ion seems more refined than it used to be. Noise and vibration are now about average for a compact car.

The front suspension has struts while the rear uses a torsion-beam axle to provide more interior space in the trunk. Again, major improvements were made last year, with new hydraulic suspension bushings in the rear and recalibrated solid bushings up front. Front and rear stabilizer bars on all models reduce lean in the corners. The Ion handles well on winding roads, tending toward understeer when driven very hard. The suspension feels a little squishy at high speeds, however. The ride is nicely damped on rough roads.

The ABS option comes with traction control and dynamic rear brake proportioning. The latter adjusts brake pressure according the load on the rear wheels. It sends more brake pressure rearward when the back seat and trunk are full. Under hard braking, it shifts brake pressure from the rear wheels to the front as the car's weight shifts forward, reducing rear-wheel lockup, for better, more stable braking.

The Ion's 2.2-liter four-cylinder engine develops 140 horsepower at 5800 rpm and 145 pound-feet of torque at 4400. This twin-cam engines gives the Ion good performance for the class. Sound deadening added for 2005 reduces filters out engine noise. Ions sold with this engine in California are certified as Super Low Emissions Vehicles (SULEV).

A new 2.4-liter twin-cam engine with variable valve timing has been added to the lineup for 2006. Like the 2.2, it's part of GM's Ecotec engine family, designed for low mass and compact dimensions. Twin balance shafts counteract engine vibration, and direct mounting of all accessories helps further reduce noise, vibration, and harshness. Optional on Ion 3 as part of the Enhanced Performance Package, the 2.4-liter develops 170 horsepower at 6200 rpm and 162 pound-feet of torque at 5000, numbers normally associated with midsize cars. The performance package includes stiffer shock valving and thicker anti-roll bars, front and rear.

A five-speed manual gearbox is standard with either engine. It works well, though the shifter is positioned slightly rearward from the ideal position.

The four-speed automatic, optional with either engine above, is a smooth-shifting unit that responds quickly to the throttle and doesn't hunt excessively between gears. Built by GM and designated Hydramatic 4T45-E, it represents a major improvement over automatics installed in 2003-04 Ions, which were built by outside suppliers. The GM transmission also allows the Ion to be flat-towed, which is why you so often see Saturns trailing behind large motor homes.

The supercharged Red Line Quad Coupe is a lot of fun to drive. It features a firmer suspension. The handling is sharper and more responsive, but you can feel and hear the bumps. The Red Line's sporty exhaust sounds good and the supercharged engine delivers good throttle response and quick acceleration performance. As with most powerful front-drive cars, there is some torque steer, but it's easy to control. The manual shifter feels tall, maybe a little ropey; but it's easy and fun to shift with easy clutch take-up. The pedals are arranged well, making it easy to heel-and-toe when braking and downshifting for corners, setting you up to accelerate out and charge down the next straight.