How Start and Stop Works

Start-Stop technology is here. Although the figures quoted vary, as many as 30-50% of new vehicles in Europe and Japan now come with variations of Start-Stop technology in place.


If you’re looking for quality starter motors online, you might need to take into consideration whether or not your car uses “Start-Stop” (also sometimes called “Stop-Start”) technology. This is an engine management technique that has been developed to address at least some of the issues arising from congested urban driving. So, what are those issues? When your car is stopped or idling in traffic jams, at junctions or traffic lights, it’s still burning fuel, generating heat and, above all, polluting the environment. All of these factors are highly undesirable at the best of times but even more so in this situation as you are simply sitting idle and not making any headway, despite the financial and environmental costs involved.

Start and Stop technology – a partial solution

Some years ago, manufacturers starting asking the fundamental question “why don’t we switch off the engine when it’s not being used?” If there is no fuel being burned because the engine is ‘off’ at, say, a red light, then many of the above problems simply go away. The common-sense notion of this is attractive but designing it into modern vehicles wasn’t easy. Firstly, the system for stopping and starting cars when they’re idling needs to be automatic, as few drivers want to be constantly pushing their start button or turning a key every few seconds when in traffic. Secondly, in terms of perceptions of performance, it had to be completely transparent to drivers and therefore free of on/off sounds, revving and excessive starter motor noise. Thirdly, it had to show real fuel cost and environmental benefits. These challenges have been largely resolved and technology that automatically stops your car when you brake or are stationary then re-starts it when you touch the accelerator is now commonplace.

Traffic jam

Benefits and trade-offs

Although people sometimes argue about the figures, it’s generally accepted that, on average, Start-Stop technology should reduce your fuel consumption by around 15% per annum – good news both for your wallet and the environment. However, this technology does make additional demands on other aspects of your vehicle.

Fuel consumption

For example, if your engine isn’t firing when your car is stopped or stopping, the vehicle’s systems will need to be powered from your battery alone – that’s quite an ask when taking into account air conditioning and music systems in lengthy traffic jams, etc. Then there is the considerable additional load placed upon your starter motor (or equivalent) in terms of constantly re-starting your vehicle in such a way as to ensure you’re virtually unaware of what’s happening. As is always the case, different manufacturers have approached the design and solution development issues in these areas differently, but the emphasis on higher-quality and higher-technology starter and power retention/transfer systems is consistent. The days of “any old thing will do” are rapidly disappearing, and now you can easily find high-quality starter motors online. 

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