"Turbo Power and Torque
The heart of any car is its engine. While the Mazdaspeed6's is a 2.3 litre twin-cam 16-valve balance-shaft-equipped four-cylinder, just like the Mazda6, "only the nuts and bolts are the same," said Kenichiro Saruwatari, assistant manager of powertrain development.
The block and heads are cast from a different aluminium alloy, the crankshaft and connecting rods are steel rather than cast iron and the pistons now have full-floating wrist pins.
But the two biggest differences are direct injection of gasoline into the combustion chamber instead of into the ports upstream of the valves, and the addition of a Hitachi intercooled turbocharger.
The direct injection generates a bunch of advantages, and enables even more. The cooling effect of the spray of fuel raises the knock threshold, which allows tuning for greater torque at low speeds; and a high-for-a-turbo compression ratio of 9.5:1, to the benefit of fuel efficiency, throttle response and emissions.
Thus, the turbo doesn't have to work as hard as it might otherwise need to, so a smaller, faster-spooling, simpler, single-scroll unit can be used to boost the mid-range, with minimal turbo lag.
North American-spec engines will generate a substantial 274 horsepower at 5500 rpm, and a very flat torque curve which peaks at 280 lb-ft at 3000 rpm, but which is virtually flat at that level from 2000 to 5500 rpm. Mazda promises a 0 - 100 km/h sprint time of 6.6 seconds; quicker than a 2.0 litre Subaru Legacy Turbo or a BMW 330i, two cars Mazda hopes customers will perceive as direct competitors.
A new six-speed manual transmission from Aisin is the only gear-swapping system available. It is extremely compact and lightweight, yet has been engineered both for short shift stroke and light effort. Contrary to typical sporty car practice, it is a wide-ratio box, to take advantage of that broad torque band."
