Topi Rönkkö, Tampere University of Technology, Finland, and colleagues investigated submicrometer exhaust particles of vehicle engines. They conducted one experiment with a heavy-duty diesel truck at on-road conditions, and two with gasoline direct injection (GDI) passenger cars at chassis dynamometer.
20−30 % of the exhaust particles larger than 3 nm is formed during engine braking conditions. The particles are nonvolatile and contain the lube-oil-derived metals zinc, phosphorus, and calcium, which make them a health risk for humans.
Breaking conditions refers to the driver’s lifting of the gas (accelerator) pedal and keeping the gear on. Typically, this is used to enhance fuel economy or to limit or decrease the speed of a vehicle during downhill driving or deceleration, e.g., at crossroads, traffic lights, or bus stops. With GDI engines, the fuel consumption during engine braking is zero.
According to the researchers these emissions can be reduced using exhaust particle filtration systems or by modifying the engine oil characteristics, such as metal content or viscosity.
- Vehicle Engines Produce Exhaust Nanoparticles Even When Not Fueled,
Topi Rönkkö, Liisa Pirjola, Leonidas Ntziachristos, Juha Heikkila, Panu Karjalainen, Risto Hillamo, Jorma Keskinen,
Environ. Sci. Technol. 2014.