Improving lower speed 4-valve engine response

By combining fuel injection into two groups and using transient compensatory fuel injection, Toyota engineers have increased the driveability of a 4-valve, 4-cylinder engine at low and medium speeds. Today's gasoline engines must provide both high power and good fuel economy, thus 4-valve engines are becoming increasingly common. However, when a 2-valve unit is modified to a 4-valve configuration, response at low and medium engine speeds generally deteriorates, although output at high engine speeds increases. Manufacturers must, therefore, improve throttle response when developing 4-valve engines. One way to obtain good response across their engine speed range is to use recent electronic fuel injection (EFI) developments to accommodate their unique induction system characteristics.