| First Drive | Frankfurt, Germany | Mazda3 with Smart Idle Start Stop |

As part of a day of technology workshops at Mazda's R&D centre in Frankfurt we were introduced to the Japanese company's innovative new start-stop system it calls Smart Idle Start Stop (SISS). Though the technology will be shown at the Paris Show next month in the Kiyora concept, it won't reach Europe until later in 2009 and the Mazda3 we drove with the system fitted to it was nothing more than a development mule cleaned up a little so the journalists wouldn't cut themselves or wreak havoc with loose wiring.

How it works

Several start-stop systems already exist, cutting the engine when the car is at rest, to the benefit of fuel economy and reduced emissions. We're very familiar with BMW's EfficientDynamics version, which is featured in all four-cylinder diesel versions of the 1 Series and 3 Series with manual gearboxes. Mazda's is a little different.

SISS only works with direct injection petrol engines, as it utilises not only the starting motor, but also the initiation of combustion itself to restart the engine. This has been made possible by the adoption of a sophisticated crank angle sensor, which can accurately pin point the position of the crankshaft and hence the location of each piston in their cylinders. On restarting, the engine management system calculates which cylinder is best suited to combustion and fuel is directly injected and ignited with the spark plug. In conjunction with the starting motor the result is a claimed 50% quicker restart than BMW manages with a larger starting motor alone.

In practise

Given the experimental nature of the test car it was hardly surprising that our only time behind the wheel was with a chaperone and around a compact slow-speed route within the R&D grounds. However, plenty of reasons to come to a stop were in place and it was enough to confirm that while the Mazda system is quicker to get going than BMW's system, the SISS also seems slower to actually stop the engine. This could well be due to the need to stop the pistons in the right place for restarting, which is cleverly done by utilising the alternator as an engine brake. The starter motor itself is new too and has been designed for quieter operation, as Mazda realises that owners will have to listen to it more frequently than in a car without SISS. The test car utilised a manual gearbox and so the stop procedure is identical to BMW's, where the engine will stop when the car is moving at less than 4km/h when the gearbox is in neutral and the driver's foot is off the clutch. Unlike BMW, Mazda has also developed SISS for operation with an automatic transmission.

Future plans

To begin with, the SISS system will only be available on a new 2.0-litre DISI (Direct Injection Spark Ignition) engine with 149bhp and 139lb.ft of torque. Powering the all-new Mazda3, it's estimated that this engine could produce less than 160g/km of CO₂. Mazda reckons the new engine, utilising SISS, improves fuel economy and emissions by about 9% on the combined cycle, though real-world gains are largely dependant on driving conditions. Following on from the introduction of SISS a whole new range of DISI engines will become available in 2011 with a target of 15-20% better fuel economy than the current petrol line-up. It's expected that SISS will eventually be standard.

As SISS employs spark ignition to speed up restarting the engine, the same system can not be applied to Mazda's diesel engines, though the company has not ruled out using a different method in the future. Mazda's next-generation rotary engine will feature SISS when it arrives in 2010.

Summary

Clever, but essentially simple ideas are behind Mazda's new Smart Idle Stop Start functionality. Though the technology will begin to arrive in 2009, it will be several years before it has an impact across the whole Mazda range, and even then only on the direct-injection petrol models. First impressions suggest that it works well with rapid engine starting and little fuss. It could have a real benefit for drivers that spend a lot of their time in traffic or in urban conditions.