The race is on among car manufacturers – and suddenly it is not a race to find the biggest and the fastest but to find the most efficient. With concerns about car emissions from consumers, and various perks and privileges being offered by governments to owners of lower-emission vehicles, the smaller-engined, greener car looks like it is finally nosing ahead on the production lines.

Renault: Case Study

Jacques Prost, senior vice president of powertrain engineering at Renault, recently highlighted that the larger 1.8 and 2.0 litre engine cars that Renault has historically produced are due to be dropped in favour of smaller motors that produce fewer emissions.

This new family of smaller petrol engines will account for the vast majority - as many as 85% - of Renault’s small cars by 2015. Indeed there will be very few cars produced with anything as powerful as a 1.4 or 1.6 litre engine, and a 2.0 engine on a small car will become a very lonely gas-guzzling dinosaur on the road to extinction.

The real savings for the environment, in the short term at least, will not be from the much-discussed breed of electric cars – let alone their hydrogen-fuelled distant relatives – but from advances made in petrol and diesel engine designs and in the use of hybrid engines.

These advances have been a long time coming and will take centre stage over the next few years as car manufacturers vie for eco-leadership. The average new car emissions have dropped by over 20% since 2000 to 144.2g/km CO2 – and the new generation of cars announced looks set to continue this trend.

Renault's Prost explained the technologies that have allowed them to maintain the power output of the old 1.9 dCi 130 with its smaller, greener replacement (the 1.6 dCi 130). The new smaller engine slashes emissions by 25g/km but you will notice no difference with how your car deals with driving conditions. Here’s how it has been achieved:

• A more efficient turbo saves 9g/km
• Stop & start functionality saves 7g/km
• New exhaust gas treatment saves 5g/km
• Improved temperature control saves 2g/km
• Additional friction gains save 2g/km

Turbo Engines

Turbo charged cars, such as Volkswagen’s TSI technology, make use of small petrol engines boosted by turbo and supercharger technology. This allows for good performance and low emissions. Car makers such as Peugeot and BMW also offer small 1.6-litre petrol engines that are boosted by turbo chargers and you can expect even smaller engines - possibly below 1.0-litre - to benefit from high-pressure turbo and supercharger technology to provide drivers with the power they want, while reducing emissions.

Hybrid Engines

Hybrid engines help reduce the size of the engine needed and its carbon footprint further by combining part battery-electric and part conventional cars. The underlying principle of all hybrid vehicles is the use of a temporary energy storage device (usually a battery), which enables the main engine to be operated at close to its maximum efficiency. It will not be long before all genres of car - from the sports car to the 7 seater SUV, from the large car to the micro car, and even on to the motorcycle - will be available in hybrid form. Toyota has claimed that it will offer all of its current vehicles with hybrid propulsion systems in the near future.

The Future Looks Small

The future, then, looks smaller in terms of the engines on offer and the emissions they will make – which is surely a good thing.