Stop-start technology has been around for a long time - with the majority of EU cars now featuring the system. Most if not all manufacturers will install start-stop on their entire fleets over the coming years.
Start-stop was first offered by Toyota in one of its sedans in the mid-seventies. Some VW Polos included the system in the early eighties.
The dual requirements of fuel economy and emissions standards have driven the technology forwards - particularly in Europe.
Fuel is more costly across the continent compared to, say, the USA, so it makes a lot of sense - and can save you as much as 10% compared to cars without start-stop. Motorists who drive in urban locations see more dramatic fuel savings because they have to start and stop more frequently.
EU legislation has also played a critical role - compelling carmakers to make their products more fuel efficient. And the better the fuel economy figure, the more attractive a car is to buyers.
Carmakers will spend huge sums to improve their fuel efficiency - even by just a small amount.
When a car comes to a stop - perhaps at a set of traffic lights - the electronics stop the engine. This only turns off the engine - none of the other systems. When the stop-start system detects a car is stationary or out of gear, it will turn off the spark to the ignition and switch off the fuel flow to the cylinders. As soon as the clutch is engaged or the brake is released, the engine will start again. This automatic process happens very quickly and far faster than turning a key on and off.
- Engine shutdown - (not overall car shut down)
- Electric assists and pumps - (not belt-driven, so things like power steering still work)
- Starter motor - this is much more durable than traditional starter motors because it has to work so much more often
- Deep cycle battery - which can be deeply discharged then readily recharged
- Air conditioning system - so heating/cooling still occurs
- Lower engine friction - for better durability (starting and stopping is tough on engines)
Hybrid cars have such powerful batteries that a separate cell is not necessary. The integrated motor can also work as a starter.
A good start-stop system will have:
- A fast restart - how quickly you can move from the brake to the accelerator
- Fewer rotations to get the engine running again
- Low body vibrations when starting and stopping
- Engine mounts - that ensure a smooth start-stop experience
- Defeatable - so it can be turned off if necessary
These factors can vary between models.