Effective exploitation of idle phases can reduce fuel consumption by five percent

Looking at the smart fortwo mild hybrid, it is clear to see that smart is not afraid of teaming up with others to maximise its competencies: the vehicle’s drive is the result of a cooperation with colleagues from the Mercedes-Benz development department. The drive (a petrol engine with an output of 45 kW/61 bhp) uses a belt-driven starter generator, which fulfils the functions of both starter and alternator. The difference between this and a hybrid drive is that the mild hybrid does not make use of braking power, nor does it have a booster function.

Starter generator reduces the time needed to drive off

Like in the smart crosstown and the smart fortwo cdi hybrid, the smart fortwo mild hybrid has an automatic start-stop system, which can switch the combustion engine off during idling phases. It also has a starter generator, which reduces the time needed to reach the combustion engine speed required for the clutch to engage. That’s a time reduction of around 0.25 seconds, meaning a further reduction in the relatively large amount of fuel consumed during starting-up.

This allows a total fuel saving of some five percent in the new European driving cycle (NEDC), which is binding for all vehicles. With the mild hybrid, the fuel consumption level of 4.7 litres per 100 kilometres which applies under standard conditions is reduced by 0.25 litres to less than 4.5 litres. In urban traffic, the smart fortwo mild hybrid uses a whole 13 percent less petrol.

Intelligent use of the automatic start-stop system

The automatic start-stop system ensures effective exploitation of the engine’s idle phases. This means that, as soon as the driver applies pressure to the brake pedal in order to bring the smart fortwo mild hybrid to a standstill from a speed of at least 10 km/h, the engine is automatically switched off. This does not just happen at red lights – it could just as easily be at a junction or a zebra crossing.

True, that isn’t always ideal. In midsummer, or on a cold winter’s day, for example, when you’re stuck in a traffic jam, you won’t want your air conditioning or heating to be suddenly switched off. That’s why there is a switch on the centre console for the easy deactivation – and subsequent re-activation – of the automatic start-stop system during driving.