The Mazdaspeed 3 is the hottest sport compact to roll this year. Check the facts: 263 hp, a fortified chassis, and a racy cabin for a base price of $22,835. Radar guns see a demure econobox. The reality is that affordability, practicality, and stealthy velocity can share the same three-legged stool.
Born two years ago, Mazda's 3 elbowed aside Honda Civics and Volkswagen Golfs to become the budget-bound enthusiast's new sweetheart. Now that Mazda's speed geeks have recalibrated the hatchback version of the 3, it's off and running toward the wild, blue, 150-mph yonder.
The transformation from wee one to wild thing involved no shock therapy or rack torture. The noble goal was an affordable front-driver capable of muscling into Mitsubishi's and Subaru's all-wheel-drive party. To begin the process, U.S.-based Mazda engineers built two project cars and mailed them to Japan for colleagues to drive and scrutinize. A few weeks in the dyno room followed by track tuning has transformed a capable compact into the quickest yearling in the stable. It may not have been Mazda's intention, but neither the RX-8 nor the Mazdaspeed 6 can keep pace with this young sprinter.
The core engine for both Mazdaspeed cars is the same long-stroke, 2.3-liter MZR four-cylinder available in most of the cars and trucks in the Mazda lineup, not to mention several Ford Motor Company vehicles. The key ingredients here are an aluminum block and head with forged-steel internals (crank and rods), direct fuel injection, and dual balance shafts. Two overhead camshafts operate four valves per cylinder. To hike output, a Hitachi Warner turbocharger hung on the aft side of the engine passes air pressurized to 16 psi forward through an air-to-air intercooler.
Pumping any engine beyond 100 hp per liter requires a robust foundation and careful tuning of intake, exhaust, and fuel-delivery systems. Squirting the fuel directly into the cylinders at 1600 psi (versus the less than 100 psi used by port-injection systems) is not only more precise, the higher pressure also yields smaller fuel droplets that vaporize almost instantly. This change of state--from an atomized liquid to a combustible vapor--absorbs heat from the cylinders. The resulting cooler environment is less susceptible to detonation and more capable of swallowing denser charges of air. Because there's less chance of detonation, Mazda engineers didn't have to reduce the compression ration very much compared with the normally aspirated MZR engine's ratio (9.5:1 turbo, 9.7:1 nonturbo). A higher compression equals more expansion during the power stroke, extra power with or without boost, and higher fuel mileage.
Plopping the intercooler atop the engine is similar to but cagier than Subaru's approach. Unlike the hairy Impreza WRX, there's no hood-mounted air grabber that screams boy racer. Instead, Mazda uses two discreet scoops straddling the winged grille badge to feed ductwork attached to the hood's underside. When the hood is closed, the duct seals firmly against the twelve-by-fourteen-inch intercooler. Ram airflow may be less efficient than the low-mounted, forward-facing intercooler used on Mitsubishi's Lancer Evo, but that arrangement requires more complex plumbing than the Mazdaspeed 3's tidy, over-the-top layout.