Software and hardware changes required to remove emission-cheating technology from Volkswagen vehicles will likely worsen fuel economy and performance, experts have said.
Work will have to be done on 11 million diesel vehicles equipped with two different types of emission-scrubbing systems which are programmed to detect when the car is being tested and take measures to minimise emissions.
Volkswagen’s new chief executive Matthias Mueller confirmed on Tuesday the cars will have to be refitted, but did not specify what this refitting would entail.
In late 2008, Volkswagen started implementing the so-called lean NOx traps to reduce concentrations of nitrogen oxides in exhaust fumes of some of its diesel cars.
According to automotive consultant Sandy Munro, technology removing nitrogen oxide emissions usually affects fuel economy and performance of diesel engines. This decrease of performance and increase of fuel consumption likely motivated Volkswagen to put a system in place that would only turn on the lean NOx traps during lab testing.
The US Environmental Protection Agency suggested vehicles using the NOx traps manufactured between 2009 and 2014 will most likely take longer to fix.
Former Volkswagen executive vice president of group quality Marc Trahan said older VW diesel vehicles could be made to function properly with a simple software fix without additional hardware changes, which would require costly re-engineering.
Changes will also have to be made to newer Volkswagen vehicles equipped with 2.0 TDI engines with the more expensive Selective Catalytic Reduction (SCR) emission control technology. SCR, used on Volkswagen’s flagship Passat model, injects a liquid urea solution into the exhaust to remove nitrogen oxides.
However, due to the high consumption of urea, Volkswagen decided to only use the systems during testing.
According to Trahan, Volkswagen found the urea solution would have to be refilled every 5,000 miles, half the usual 10,000-mile interval required for engine oil changes.
A software patch would probably be enough to fix the SCR problem, experts said, but at a cost of increased urea use and reduced vehicle performance and fuel economy.
Some analysts have estimated removing the emission cheating software could come with an overall price tag of more than $6.5bn.
Volkswagen Group new CEO infographic