Mazda Motor Corp. DISI 2.3L Turbocharged DOHC I-4
By Bill Visnic WardsAuto.com, Dec 20, 2006 9:03 AM

You’ve seen those percussion grenades thrown in action films: Pull the pin, toss it in the room, there’s a big bang and blinding flash, and everyone in the room is rendered senseless.

Imagine the analogue in the engine world, and you’ve got Mazda Motor Corp.’s DISI 2.3L turbocharged DOHC I-4 all but blasting its way past the competition for its second consecutive 10 Best Engines award.

Total sensory overload is how we’d describe testing Mazda’s ultra-power-dense 4-cyl. in the new Mazdaspeed3 application. Turning the key and lighting off this big-boost variant of the Mazda-developed MZR 4-cyl. architecture – also used by part-owner Ford Motor Co. – is the equivalent of pulling the pin.

From there, 114 hp per liter in a car that weighs 3,180 lbs. (1,443 kg) and, well, we’ll do the math for you: 12 lbs. (5.4 kg) per horsepower. That’s spittin’ distance from high-dollar hardware such as Porsche Cayman (11.7 lbs./hp) or even Mazda’s own sports-car flagship, the RX-8 (13 lbs./hp).

But this is an engine award, so consider that with its 15.6 psi (1 bar) of boost pressure ramming out 280 lb.-ft. (380 Nm) of torque, this 2.3L 4-cyl. out-torques Porsche’s 3.4L DOHC H-6 in the $59,000 Cayman S and, really, just about any other normally aspirated 6-cyl. around.

Moreover, this firecracker 4-cyl. rams the Mazdaspeed3, incredibly, to a stated top speed of 155 mph (250 km/h) and runs 0-60 mph (97 km/h) in less than 6 seconds.

Mazda combines turbocharging, direct-injection for 2.3L 4-cyl.'s high power density.

But the DISI 2.3L turbocharged DOHC I-4 is more than a bang-for-the-buck, strap-on-a-turbo special. There’s serious engineering at play here, the kind of action that elevates this engine above others we’ve tested that offer a great performance-per-dollar quotient.

For one, there’s Mazda’s first use of direct-injection gasoline technology. The new-age, higher-pressure fueling naturally bolsters low-rpm torque, making it the perfect technology to counter turbo lag. First seen on high-dollar engines, the technology quickly is sifting into the mainstream to the benefit of us all.

Mazda engineers also have addressed noise, vibration and harshness concerns. The aluminum block has been braced to absorb the higher stresses, and the twin balance shafts certainly seem to be earning their keep.

It would’ve been enough to generate the giant power numbers and call it a day, but this engine never gives the sensation that refinement got “costed.”

And, under the Mazdaspeed3’s hood, it’s advisable to hang on when the turbocharger hits its stride, because there’s still a not-totally-civilized wallop.

Some 10 Best Engines testers admit to preferring Mazda’s mini-dynamo DISI 2.3L turbo I-4 in the CX-7 cross/utility vehicle or the Mazdaspeed6 midsize sedan (both of which calm this brute with all-wheel drive), but all agree this engine is a special example of affordable-engine development.

bvisnic@wardsauto.com