When launching the latest VW Golf Herbert Diess, chairman of Volkswagen, says the trend of making engines smaller is over. This will end the last decade’s trend of development where engine capacity has been reduced to typically 1000cc three cylinder engines.
“Emissions tend to go up as engines get smaller,” he said, referring to the way that small-capacity engines can perform worse in real world Driving Emissions Tests due to be introduced in Europe in 2019 as part of the Worldwide Harmonized Light-duty Vehicles Testing Procedure. Diess says VolksWagen will continue with its 1.0-litre, three-cylinder engine for its smaller cars such as the Up and Polo, but it will not be developing smaller petrol engines than that and its diesel units will not be getting smaller than that current 1.6-litre unit, either. “Small diesels are just not economic,” he says. “The Polo is currently 30 % diesel, but as diesel gets more expensive, it will not be as popular.”
“The diesel market, which in some European countries take more than 50 % has not been a customer choice” he says. “They are the result of tax systems favouring the diesel. Make it cheaper and people play along” he says. So even though next next generation Polo will be available with a diesel engine Diess is not so sure it’s successor will be available with an oil-burner.
“It is difficult to predict,” he says. “If you look at the difference between the current test cycle and RDE it is hard in Germany, where tests only require between nine and 10 kilowatts (12 to 13 bhp), but on the autobahn you need 100kW (124 bhp) to do 200km/h”.
He says the disparity between current tests and real-world consumption and emissions is also wide in China where drivers sit in traffic most of the day, but the new American tests, which have effectively added 40 per cent to the total emissions detected in tests, have narrowed the gap. His opinion echoes a Reuters report last autumn which stated that new emissions tests had exposed flaws in downsized engines. In real life, the report stated, these turbocharged units have a tendency to overheat when their tiny turbos are called on to deliver real-world performance. To combat this, the engine’s software strategy will over-fuel the engine, which results in increased emissions of CO2, oxides of nitrogen as well as unburnt hydrocarbons, particulates and carbon monoxide.