Car makers such as Volkswagen, Renault and Vauxhall will slow the development of downsized engines and bring back larger capacity units following the introduction of new emissions tests, according to reports on Reuters.
Reuters says that the implementation of new real-world 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 by 2019, shows it more clearly.
Common issues in smaller units include overheating that requires over fuelling to keep engine temperatures cool. This, in turn, results in more unburned hydrocarbons, particulates and carbon monoxide.
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, when new 2019 architecture is launched, with the smallest diesel engine in the future range likely to be around 1.5 litres in capacity.