The introduction of new real-world testing procedures will see carmakers such as Volkswagen, Renault, and Vauxhall slowing down the development of their downsized engines and bringing back larger capacity units, according to reports on Reuters.

Reuters reports that the implementation of the new emissions testing procedures has exposed flaws in downsized engines, which were predominantly developed to achieve low emission ratings in older laboratory tests. New real-world data has shown that downsized units can sometimes perform worse than larger ones for CO2 and NOx output, largely because of the heat generated by their turbos, which they depend on more to develop power.

While lab tests were unable to reveal these downfalls, new real-world testing, which will come into force in Europe by 2019, shows it more clearly.

Pavan Potluri, an analyst at forecasting company IHS Automotive, told Reuters: "[Downsized engines] might be doing okay in the current European test cycle, but in the real world, they are not performing. So there's actually a bit of 'upsizing' going on, particularly in diesel."

According to Reuters, several car makers have already started to work this ‘upsizing’ philosophy into production models. General Motors is said to be ditching its 1.2-litre diesel engine, which features in models such as the Vauxhall Corsa in international markets. When the carmaker’s new 2019 architecture is launched, the smallest diesel engine in its future range will likely be around 1.5-litres in capacity.

Volkswagen is also replacing its 1.4-litre three-cylinder diesel engines in international markets with four-cylinder 1.6-litre motors in smaller models. Meanwhile, Renault is also making a U-turn by introducing a 10 percent larger unit in place of its R9M 1.6-litre diesel, which itself was a downsized unit that filled the space left by a discontinued 1.9-litre diesel.

These reports come at a time when companies like Porsche have employed downsizing in their models. However, in the future, downsizing might come in the form of increased hybridisation, rather than the shedding of cubic centimeters.