TOUGHER European car emissions tests being introduced in the wake of the Volkswagen scandal are about to bring surprising consequences: bigger engines.

    Carmakers that have spent a decade shrinking engine capacities to meet emissions goals are now being forced into a costly U-turn, industry sources said, as more realistic on-the-road testing exposes deep flaws in their 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, the people said. Other manufacturers are expected to follow, with both diesels and gasolines affected.

    The reversal makes it even harder to meet carbon dioxide (CO2) 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, which ends Saturday. Renault, VW and GM’s Opel all declined to comment on specific engine plans.

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

    These mini-motors sailed through official lab tests conducted — until now — on rollers at unrealistically moderate temperatures and speeds.

    (SD-Agencies)