For Mazda Motor Corp's "CX-8" SUV (sport utility vehicle) having three rows of seats, the company made improvements to the "Skyactiv-D 2.2" 2.2L diesel engine, which is also used for the "CX-5" SUV.
Mazda remodeled the Skyactiv-D 2.2 to ensure enough power and prevent fuel efficiency deterioration for the CX-8, which is for many passengers and the company's largest vehicle (dimensions: 4,900 (L) x 1,840 (W) x 1,730mm (H), weight: 1,790-1,900kg).
The maximum torque and maximum output of the CX-8 are 450N·m and 140kW, respectively, which are significantly higher than those of the CX-5 (maximum torque: 420N·m, maximum output: 129kW). The fuel efficiency of the CX-8 (front-engine, front-wheel-drive (FF) vehicle) is 17.6km/L (approx 41.4mpg), which is close to the fuel efficiency of the CX-5 (FF vehicle), under the JC08 test mode.
By making improvements to the engine, Mazda made up for the vehicle weight increase of about 200kg (compared with the CX-5).
The employment of a variable geometry turbocharger contributed to the improvement of maximum torque and maximum output. A variable geometry turbocharger uses a variable nozzle in the housing of the exhaust gas turbine for changing the cross-section area (aperture) and orientation of the exhaust gas passage.
At low engine rotation speeds at which there is a shortage of the amount of flowing exhaust gas for turning the exhaust gas turbine, the variable nozzle is used to narrow the cross-section area and controls the engine so that exhaust gas hits the edges of the turbine blades. As a result, it becomes possible to turn a large turbocharger even with a small amount of flowing exhaust gas.
Thus far, Mazda has been using this technology for the "Skyactiv-D 1.5" 1.5L diesel engine. And, this time, the company applied it to the Skyactiv-D 2.2.