Before emission-free electric vehicles fill our roads, there are a number of improvements that car makers can make to internal combustion engines to reduce emissions while they continue to bear the burden of most of the world’s transport needs.
Gasoline direct injection (GDI) combustion with lean stratified operation reduces toxic engine emissions and achieves significant benefits in fuel consumption. So far so good. However, using the precise high air/fuel ratio for lean stratified operation can also have some disadvantages, including engine instability, power loss and increased nitrogen oxide (NOx) emissions. Using multiple gasoline injection strategies can minimize these problems. But, these strategies require the delivery, via the injectors, of very small amounts of fuel, in very accurate doses. And then there is an engineering problem too: to deliver the very small amounts of fuel, traditional solenoid injectors are forced to work in their “ballistic” region, where the correlation between coil energizing time and injected fuel amount becomes highly non-linear!