What is it?
Technically, it’s Mazda’s first model to be offered with a fuel-saving, emissions-lowering stop-start system. But, for reasons we’ll get on to, it’s easier to think of this car as a lukewarm version of the Japanese car maker’s facelifted 3 hatchback, which just happens to have some new and interesting engine technology.
As anyone who’s checked out this car’s vital statistics will have already observed, this car might have commendable fuel economy and emissions for a 148bhp petrol-powered five-door, but it’s no rival to Ford’s Focus Econetic on either fuel economy or CO2 emissions.
Mazda has been developing its own engine idle stop-start system for some time. It’s different from other systems because it doesn’t include a conventional starter-generator. Instead, Mazda’s system restarts the engine after a brief halt in traffic using a slightly more sophisticated and more powerful starter motor and Mazda’s own ‘DISI’ direct injection system.
The system automatically stops the engine when it detects the time is right and, once stopped, it automatically aligns the engine’s pistons towards the middle of their stroke. Using crankshaft position sensors it detects which piston is on a power stroke and, the instant you hit the clutch to move away again, it simply injects fuel into the cylinder, ignites the mixture, and uses the starter motor to put enough kinetic energy back into the crank to get it spinning again.
Mazda says its system is faster to restart and creates less vibration than a conventional starter-generator. But it does only work on direct injection engines...
Given that it had already added direct injection to the 3 MPS’s 2.3-litre turbo motor, and allowing for the fact that it simply wants to roll out DISI and i-Stop technology throughout its petrol engine range as quickly as possible, the easiest first step for Mazda was to add direct injection to the related 2.0-litre before it adapted it for the smaller 1.6-litre petrol four. Eventually it will adapt the system to work with its diesel engines too, but there are hurdles to overcome when dealing with compression ignition.