Car engines to increase in size following VW emissions scandal

This represents a costly U-turn for the industry which has spent a decade shrinking engine capacities to meet emissions goals.

But new, more realistic, on-the-road testing regimes have exposed deep flaws in some of the smallest motors.

Renault, General Motors and VW are preparing to enlarge or scrap some of their best-selling small car engines over the next three years, according to industry sources. Other manufacturers are expected to follow, with both diesel and petrol engines affected.

But the reversal makes it even harder to meet carbon dioxide targets and will challenge development budgets already stretched by a rush into electric cars and hybrids.

“The techniques we’ve used to reduce engine capacities will no longer allow us to meet emissions standards,” said Alain Raposo, head of powertrain at the Renault-Nissan alliance.

“We’re reaching the limits of downsizing,” he said at the Paris auto show. Renault, VW and GM’s Opel all declined to comment on specific engine plans.

Following revelations last year that VW was using ‘cheat devices’ to alter the perceived emissions produced by their vehicles in regulatory pre-release vehicle testing, authorities have shaken up their testing procedure to more accurately represent true-life driving conditions.

Starting next year, new models will be subjected to realistic on-the-road testing for NOx, with all cars required to comply by 2019. Fuel consumption and CO2 will follow two years later under a new global test standard.

Although other car manufacturers may not have been using cheat devices, their vehicles also breached emission limits when driven in real-world driving conditions.

VW has suffered financially from the scandal and was forced to repair or buy back polluting US diesel vehicles in June and pay owners up to £7,500 under an £11bn deal with US authorities. 

Despite this, VW became the world’s top-selling carmaker in the first six months of 2016, overtaking rival Toyota, due to a series of production stoppages affecting the Japanese manufacturer. 

For years, carmakers kept pace with European Union CO2 goals by shrinking engine capacities, while adding turbochargers to make up lost power. Three-cylinder motors below one litre have become common in cars up to VW Golf-sized compacts; some Fiat models run on twin-cylinders.

While these mini-motors sailed through the official lab tests, they were conducted on rollers at unrealistically moderate temperatures and speeds.

Carmakers’ smallest European engines, when driven at higher loads than current tests allow, far exceed legal emissions levels. Heat from the souped-up turbos generates diesel NOx up to 15 times over the limit; gasoline equivalents lose fuel-efficiency and spew fine particles and carbon monoxide.

“They might be doing OK in the current European test cycle, but in the real world they are not performing,” said Pavan Potluri, an analyst with influential forecaster IHS Automotive.

“So there’s actually a bit of ‘upsizing’ going on, particularly in diesel.”

Carmakers have kept understandably quiet about the scale of the problem or how they plan to address it. But industry sources shared details of a retreat already under way.

GM will not replace its current 1.2-litre diesel when the engines are updated on a new architecture arriving in 2019, people with knowledge of the matter said. The smallest engine in the range will be 25-30 per cent bigger.

VW is replacing its 1.4 litre three-cylinder diesel with a four-cylinder 1.6 for cars like the Polo, they said, while Renault is planning a near-10 per cent enlargement to its 1.6 litre R9M diesel, which had replaced a 1.9-litre model in 2011.