SPEED TREATED; 2007 MazdaSpeed3 pushes pocket rocket envelope.(News)

Byline: ROGER HART

Mazda didn't invent the sport compact, but it seems fairly intent on making sure those who care about pocket rockets pay attention to the cars coming from Hiroshima.

Case in point: the 2007 MazdaSpeed3. With a 2.3-liter turbocharged, direct-injected four-cylinder making 263 hp and 280 lb-ft of torque, this Mazda will dust the VW GTI and Honda Civic Si-two of the Speed3's major competitors-in a drag race. Mazda claims sub-six-second 0-to-60-mph times, and in our first test of the car we found it to be a tire-smoking ball of fun to drive. Spool up the turbo, drop the clutch, and it will smoke the 18-inch sport tires all the way through first gear, give you a loud chirp when you grab second and another in third.

To handle cornering loads, Mazda engineers beefed up the chassis, adding supports to the front and rear suspension mounts to keep the wheels from changing camber during hard corners, and stiffened the center tunnel. The extra steel adds 15 pounds to the MazdaSpeed3's chassis over a standard Mazda3.

The Direct Injection Spark Ignition engine is the same powerplant used in the MazdaSpeed6 and the CX-7. The compact design has the intercooler mounted on top of the engine with ductwork beneath the hood routing cool air to the intake.

The key to the engine's power, says Ruben Archilla, Mazda's general manager for product development, is direct fuel injection. "With fuel pressure of 115 bar [115 times atmospheric pressure], we get a precise injection of fuel close to where it will be ignited. As the fuel is injected into the cylinder there is a rapid drop in pressure, which cools the fuel and gives a denser charge. A denser charge gives us more torque, a faster turbo spool-up and a faster catalyst heat-up for better emissions,'' Archilla says.