Mazda CX-5: A new bag of tricks

By Alastair Sloane

Mazda has changed the rules on fuel combustions for the CX-5, making it more economical and more powerful. Photo / Supplied
Mazda has changed the rules on fuel combustions for the CX-5, making it more economical and more powerful. Photo / Supplied

Mazda will unveil its complete SkyActiv bag of tricks for the first time in New Zealand when it launches the mid-range CX-5 SUV next month.

SkyActiv is a bunch of technology with which Mazda aims to drastically improve fuel economy. The powertrain - engine and gearbox - is at the core of the system, and Mazda claims it delivers more power and torque but cuts fuel use by around 25 per cent.

SkyActiv also includes lighter-weight materials - the bumpers are made of resin, for example - and improved aerodynamics. The chassis contains straight, lightweight steel sections to form the body shell's reinforcement channels.

The CX-5 is available in front- or all-wheel-drive with the choice of SkyActiv G (2-litre petrol) and D (2.2-litre diesel) engines mated to a six-speed automatic gearbox with manual mode.

The heartbeat of SkyActiv is more efficient combustion, improved cooling, a largely conventional automatic gearbox with the precision of a Volkswagen-type DSG unit but considerably lighter in weight, and an improved exhaust manifold.

The big news is compression ratios. Mazda has changed the rules of combustion by increasing the ratio in its spark-ignition petrol engines and decreasing it in compression-ignition diesels.

For years, petrol engines with carburettors ran at a ratio between 8:1 and 9:1. Direct fuel injection moved the ratio on to 10:1 and as high as 12:1. That was as good as it got before the risk of "detonation", when the fuel ignites too early in the combustion process.

Mazda overcame that problem by using crowned pistons with a saucer-like cavity in the centre (much like a diesel engine), valve gears that can be adjusted to change the operating cycles and improved fuel injection to enable the 2-litre Skyactiv G engine to run at 14:1 on 91 unleaded, a ratio that means a better bang when the fuel/air mixture ignites. (The SkyActiv Mazda3 runs at 12:1, an agreed ratio for New Zealand and Australia.)

The result is that more of the power in the fuel is used to drive the vehicle rather than being lost in the exhaust or cooling systems, or through mechanical resistance or friction.

The diesel engine in the CX-5 is another breakthrough. SkyActiv D lowers the traditional diesel compression ratio from 17:1 to 14:1, enabling the 2.2-litre oil-burner to rev to 5200rpm and beyond - the current best run out of puff around 4400rpm.

A brief drive around central Auckland in the 2-litre CX-5 showed a petrol engine with good power delivery all the way to 114kW at 6000rpm and beyond.

The engine remained strong but bellowed a bit under the throttle as the six-speeder searched for a suitable gear to get the roughly 1600kg CX-5 up a steeper suburban street.

A repeat of the climb using the gearbox's manual mode and a lighter throttle opening kept the noise down.

Ride and handling is first class for a higher-riding SUV. The driving position is a cracker and cabin design and fit and finish is a step up from others in the Mazda range. But the black-on-black trim throughout becomes a tad dreary on the eyes very quickly.

The raked windscreen and deep side windows offer visual relief from front and rear seats with more than enough room. The rear seats are easy to fold flat for added cargo room.

In a nutshell, the CX-5 is going to be a serious rival for the established brands in the growing medium SUV market.

- NZ Herald

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