Engine downsizing could cause emission problems

The recent trend of downsizing combustion engines to reduce their environmental impact could cause "problems" for manufacturers if the trend continues, says Volkswagen boss Herbert Diess.

In an interview with Autocar, Diess said that downsizing had "achieved its goals" as the reduction in engine cylinders had brought "efficiency benefits while retaining the qualities of driveability."

While he said that the downsizing trend "made a lot of sense", he also said it could "come to an end now". Otherwise the company risked running into emissions and cost problems.

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Diess told the magazine that the stricter emissions tests for diesel units could mean the combustion engine would be replaced by a "48V hybrid system".

He added: "The internal combustion engine has a long life ahead of it yet, but as we hit the limits of thermo-dynamics, then the cost of hybridisation will be less than that of pursuing gains without them."

Diess's comments follow Volkswagen's announcement of a pair of one-off Golfs designed by their apprentices. These feature performance hybrid systems, indicating that the firm is committed to combustion technology.

Although the 404bhp Golf GTI and GTE Estate Impulse won't make it to production, AutoExpress says that it's "possible that the powerful 2.0-litre engine in the GTI and the uprated batteries in the GTE will make it to future road cars."