DETROIT — When Volkswagen submits a plan to fix emissions-cheating diesel engines Friday, it will have only two options for most of the cars.
It can install a bigger exhaust system to trap harmful nitrogen oxide or it can retrofit a chemical treatment process that cuts pollution.
The bigger exhaust probably will hurt performance and gas mileage, angering car owners. But the chemical treatment, while saving acceleration and mileage, needs a clumsy storage tank and multiple hardware changes to work.
In either case, almost half a million cars would have to be recalled for the repairs.
Experts say both options will be expensive, perhaps so costly that it will be cheaper to buy back some of the older models.
“I think they know right now how to do the fix,” said Alan Baum, a consultant in Detroit who advises automakers on fuel-economy regulations. “The harder part of this is … how do you actually execute it?”
VW has until Friday to submit a draft plan to fix four-cylinder diesels to the U.S. Environmental Protection Agency and the California Air Resources Board, the two agencies that forced the German automaker to admit to the cheating.
The company was to meet with the agencies Thursday, with a final submission Friday. VW’s board also is to meet Friday and might discuss the repairs.
The plan, likely to have several options for regulators to consider, must be tested by the agencies.
