Mazda has announced that its upcoming new CX-9 full-sized crossover will be powered by a turbocharged 4-cylinder engine, keeping with the theme of offering smaller, more power engines in larger vehicles.
The engine of choice is based on the large 2.5-litre direct injected “four” from the Mazda6 sedan. Here, it has been fitted with a turbocharger to make it the first turbocharged engine in the SkyActiv-G engine family. Horsepower is boosted to 227 (the normally aspirated 2.5 makes 184 hp) and torque is two-thirds greater, at 310 lb-ft (the normally aspirated unit makes 185), which Mazda compares to that of a 4-litre engine. Peak torque is achieved at just 2000 rpm, whereas the normally aspirated 2.5-litre -4-cylinder makes185 lb-ft at 3250 rpm (in front-wheel drive models, and at 4000 in AWD)
Yet, fuel economy remains fairly equal to that of the non-turbo version, thanks to (a) the Dynamic Pressure Turbo that can vary the degree of exhaust pulsation relevant to engine speed, and (b) a cooling exhaust-gas recirculation (EGR) system.
The Dynamic Pressure Turbo technology closes a series of valves at low engine speeds in order to take advantage of each exhaust pulse to drive the turbine. At higher revs, the valves open wide because the exhaust flow is sufficient to keep the turbine spinning.
The compression ration is 10.5:1, which is considerably less than that of the second generation of SkyActiv-G engines (rumoured to be as high as 18:1), but is still one of the highest in the industry for turbocharged engines.
Unveiled at the 2015 Los Angeles Auto Show, the 3-row CX-9 — the second generation of the vehicle introduced in 2006 in partnership with Ford, and which has gone through several refreshes — is due in North American showrooms in spring 2016.