Mazda's SkyActiv technology is not just a couple of engines, a torque converter or a transmission--it is a whole new, more efficient way of engineering cars.

While every carmaker is eventually going to have to make electric cars, hybrids and maybe even fuel cells, Mazda thinks that, for the more or less immediate future, we're going to continue using internal combustion. So Mazda tweaked the heck out of internal-combustion processes that have been in place for more than 100 years, coming up with solutions that make you wonder why no one else has done this stuff.

Normally high compression would result in pre-ignition, or knock, blowing holes in pistons. The longer 4-2-1 header manages backflow and reduces the amount of hot exhaust gas getting back into the combustion chamber, which in turn reduces temperature and helps prevent knock. The lower temp mixes the air and fuel more completely. A uniquely shaped piston crown also helps. As a result, torque goes up by 15 percent from 1,000 rpm to 4,000 rpm, and fuel economy goes up 15 percent, to 40 mpg highway. Peak output for the 2.0-liter gasoline engines we drove was 165 hp and 155 lb-ft of torque.

The diesel is different. Diesels need high compression of about 18:1 to operate efficiently. But Mazda found that by lowering compression to 14:1, the fuel and air could mix better and therefore burn more completely. High-pressure, multihole piezo injectors, a two-stage turbo and variable valve timing on the exhaust further cleans up combustion. Oxides of nitrogen and soot are both lower than in a conventional diesel without requiring urea injection.

For more on these technologies, visit www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-d.html.

Torque is routed to new transmissions. The SkyActiv-Drive automatic has a multiclutch torque converter that locks up quicker and more often. The SkyActiv-MT manual has a shorter-throw shifter and a more efficient routing of torque through the gearsets.

Other SkyActiv changes include a lighter, tighter chassis and greater use of aluminum in the suspension. The Mazda 6-size platforms we drove are 220 pounds lighter by efficiently designing the body and adding more high-strength steel.

What is it like to drive?

We got to pilot some new SkyActiv gasoline and diesel powertrains packaged inside several riveted-together engineering mules (officially called Technology Prototype Vehicles, or TPVs) sporting the bodywork of current Mazda 6 sedans and the chassis and drivetrains of new SkyActiv vehicles that we assumed were Mazda 6-size. The first thing we noticed was that the new torque converter on the automatic did, indeed, make for faster, tighter shifts, both up and down. It rivals dual-clutch automatics but with greater versatility. The manual shifter felt light and tight, too, though we didn't quite get the promised "feel of an MX-5."

The 2.2-liter diesel engine revved beyond its incredible 5,200-rpm redline and pulled strong the whole way. Most conventional diesels drop off much sooner. The diesel makes 310 lb-ft of torque from 2,000 rpm and 173 hp at 4,500 rpm. It felt as strong as the conventional 2.5-liter Mazda 6 we also piloted. Mazda says the SkyActiv-D makes 20 percent better fuel economy, too. It still had that somewhat rattly diesel sound to it, though.