Review of the new Mazda3 2.0 DISI I-Stop

A car that isn't moving shouldn't produce any harmful emissions or burn any fuel. It makes sense when you think about it, especially in towns and cities where large parts of so many journeys involve long motionless periods. It's only recently that the technology to eliminate emissions from stationary vehicles has become readily available in production cars and these stop/start systems are only going to become more widespread as refinements are made. Mazda has one of the most advanced set-ups of the current crop and it's fitted to the 2.0 DISI i-stop version of the Mazda3.

One problem with some stop/start technologies is that they are relatively inconvenient. It's possible for any motorist to save fuel by simply turning off their engine when waiting at traffic lights or stuck in a jam but how many of us could be bothered to do that on a regular basis for the comparatively small savings on offer? Stop/start technology took this premise to the next level but many early systems weren't hugely user-friendly. Even motorists who have the technology fitted to their cars may not use it as much as they could because it's slow to respond or it requires the brake pedal to be depressed and the car to be taken out of gear in order to activate. Mazda's i-stop is altogether cleverer and aims to offer a more seamless integration with the way we drive already.

Mazda has mated its i-stop stop/start system to the 2.0-litre DISI powerplant. It's a lively 149bhp petrol engine but in a Mazda3 range that also includes a 104bhp 1.6-litre petrol unit along with various diesels, it doesn't look like the obvious choice to form the basis of a standard bearing economy model. Mazda says that the aim was to achieve a "mix of driving fun and environmental compatibility" which sounds appealing enough. In reality, the 2.0 DISI can accelerate from zero to 62mph in 10.4s which isn't dramatically quick considering the power it has at its disposal. The i-stop system itself is integrated closely with the direct injection engine, enabling it to restart itself using combustion energy with only a little help from the starter motor. This means super-fast restarts in just 0.35s and that the driver only has to depress the clutch when the vehicle is stationary for the system to activate and stop the engine.

"Mazda has done some very clever work with the i-stop version of its Mazda3"

The Mazda3 rides on a sophisticated chassis with MacPherson strut front suspension and a multi-link arrangement at the rear. It's a configuration the car shares with the sharpest handling models in the family hatchback class. Mazda has also paid great attention to the 3's chassis rigidity and electro-hydraulic power steering in pursuit of a sporty driving experience. The results are first class with the car achieving the desired sporty feel without going over-firm on the suspension settings and forgoing ride comfort.

There are some minor aerodynamic modifications made to the i-stop version of the Mazda3 to further enhance its efficiency but you'll be hard pushed to spot these. The majority of the changes have gone on underneath the skin and there are quite a few of them. I-stop relies on sensors monitoring the precise positioning of the pistons in the cylinders at the moment the engine is cut off. Its computer software can then determine which of the cylinders will be most efficient for restarting later. The car has two batteries, a main one and a secondary unit which is used exclusively to help in restarting the engine. This means that when the engine is cut off, all of the car's electrical systems continue to function. If full cooling is required from the climate control system, the engine restarts automatically to make sure this is possible. The engine will not cut out while in its warm-up phase to ensure the exhaust gas treatment system can reach its optimum operating temperature and the engine will not cut out if the car is on a gradient of more than 14% for safety reasons.

Mazda is determined that its products will no longer pass under the radar of buyers and has fashioned an adventurous design direction to see to it. The lines are almost organic in the way they curve around the vehicle's surfaces while the narrowly contoured headlights and the black grin of the huge central air-intake provide a malevolent feel to the front end. Mazda has aimed to retain some of the aggression and sporting focus of the exterior inside where the instruments are housed in two heavily hooded binnacles and the dash is divided in to curved tiers that mirror the bodywork, the upper one displaying important information in the driver's eye-line. The seats are supportive and the handbrake and gear lever are mounted high-up within easy reach. The hatchback bodystyle provides good rear passenger accommodation with plenty of space for a couple of six-footers and a big boot with 340-litres of capacity.

Safety has been a major motivating factor in the Mazda3's design with all models getting six airbags, ABS with EBD, DSC stability control and the ESS system that flashes the hazard lights to warn vehicles behind of sudden braking. On the options list are features like RVM Rear Vehicle Monitoring, tyre pressure monitoring and a heated windscreen.

Mazda has developed a series of other technological features to help the latest 3 keep pace in the fast moving family hatch market. A Multi Information Display is included to bring together all relevant information from the car's trip computer, stereo and navigation system into one easy to use readout in the instrument cluster. There's also a special lighting system that's available as an option that turns on various cabin lights in sequence as you enter, a kind of luminescent welcome mat.

The i-stop technology in the Mazda3 is undeniably clever but customers will be more interested in the end results than how they are achieved. With combined economy of 41.5mpg and emissions of 159g/km, this isn't a particularly fuel-efficient car in the context of the wider family hatch market. Mazda's own 1.6-litre petrol engine manages 45mpg and if buyers go for the entry-level diesel model, there's an outstanding 62mpg combined economy figure.

The i-stop will perform better by comparison in urban areas where more time is spent stationary with the engine off but buyers focused on getting the best all-round economy are unlikely to be convinced by this model's bottom line. Insurance costs will also be higher than other economy models thanks to that 2.0-litre engine.

Mazda has done some very clever work with the i-stop version of its Mazda3 family hatch. The technology sets new standards in the field of stop/start technology but matched to a 150bhp 2.0-litre petrol engine, it always had its work cut out to return the kind of economy and emissions figures that the greenest models in the class now produce. Buyers seeking a mix of economy and performance are more likely to find what they're looking for in the Mazda3 i-stop than those who are focused on cutting costs.

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