The 2007 Mazda CX-7 - MZR 2.3L DISI Turbo Engine | Part Four

Balance of Ample Power and Environmental Performance: MZR 2.3L DISI Turbo Engine

The heart of every Mazda is its spirited powertrain. Under the bonnet of the Mazda CX-7 is a version of the turbocharged and intercooled 2.3-litre four-cylinder direct-injection petrol engine that powers the highly regarded Mazda6 MPS sports saloon. Engineered to deliver high performance at all speeds, along with low exhaust emissions and excellent fuel economy, Mazda’s MZR 2.3 DISI (Direct Injection Spark Ignition) turbo-charged engine produces an enthusiastic 244 horsepower at 5,000 rpm in the Mazda CX-7.

Key engine features are an aluminum block and head construction with forged internal components - crankshaft and connecting rods - for long-lasting durability. Balance shafts curb noise and vibration. A large air-to-air intercooler and direct fuel injection cool temperatures inside the cylinders. Changing the petrol’s state from liquid to vapour through the intake manifold to the cylinders provides the substantial cooling effect. The low charge temperature permits use of a high compression ratio - 9.5:1 - which boosts low- and mid-range torque by approximately 10 per cent over conventional turbo engines.

A notable change from the Mazda6 MPS engine is a new turbocharger. The refined area of the turbine inlet port enhances throttle response at low rpm and minimises turbo boost lag. When the driver nudges the throttle, vigorous acceleration is like a much larger displacement engine - one approaching twice the size of the 2.3-litre MZR engine - but without the extra weight that hampers agility and the extra fuel consumption that boosts emissions and operating costs.

The MZR 2.3 DISI turbo engine’s torque peaks at a low 2,500 rpm when 258 lb-ft of torque is available. The engine is tuned so that the muscular feel of torque begins at 2,000 rpm, and it maintains at least 99 per cent of the maximum torque all the way to 5,000 rpm, where peak horsepower is delivered. This 3,000 rpm spread of robust torque is part of what makes Mazda CX-7 such a fun-to-drive vehicle.

Low exhaust emissions are achieved by connecting the catalytic converter directly to the turbocharger to speed warm-up and shorten the time required for the catalyst to become effective. The Mazda CX-7 targets stringent U.S. federal Bin 5 and California LEV-II emissions standards.

Determined Drive

Advanced transmission and drive components pass the engine’s power cleanly and efficiently to the road surface. The six-speed Sport AT transmission provides the full manual control demanded by assertive drivers. Gear shifts are crisp, in keeping with Mazda CX-7’s sportscar character.

Two drivelines are offered: Front-Wheel Drive or Mazda’s Active Torque-Split All-Wheel Drive. The latter system uses a computer-controlled coupling integrated with the rear differential to deliver up to half the available torque to the rear wheels on demand. Sensors monitor engine information, individual wheel speeds, Anti-lock Brake System (ABS) operation, and the Mazda CX-7’s standard Dynamic Stability Control (DSC) system, to optimise torque distribution. Whether the driving conditions are dry and fast or slippery and moderately paced, exceptional road holding and handling are assured.

continues... | Part Five
Published 6 January 2005 Melanie Carter

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