GDI is Like A Diesel Engine
What you hear is normal for a Gasoline Direct injection (GDI) engine.
A GDI engine is almost identical to a Diesel engine. Both have high compression ratios. But instead of diesel, gasoline is injected under high pressure into the combustion chamber of each cylinder rather than the intake port in a fuel injection system. The result is reduced fuel consumption and emissions, especially when the engine is cold. Increased power output is also a result.
The Kia 2.4-liter four-cylinder GDI Theta II engine has a compression ratio of 11:3:1. A high-pressure fuel pump sends fuel to the injectors and helps bring output to ~200 hp and ~184 lb-ft of torque. Compared with a conventional engine of the same size, the GDI Theta II delivers 7 percent more torque on the low end, 12 percent more at the high end and as much as 10 percent better fuel economy.
Other engine features include a three-stage variable induction system that helps create an optimal air-to-fuel mix as well as Dual Continuously Variable Valve Timing to improve engine breathing. A lightweight crankshaft and catalytic converter also eliminate some weight to further increase the four-cylinder's fuel economy.
The power and fuel savings are even more impressive when a turbo is added to the mix.
Check out this video on Hyundai's version of the engine (which is probably the same engine with different branding).
Regards,
JC