For example, the some GDI engines can adjust the timing so that a smaller amount of fuel is injected during the compression stroke, creating a much smaller, controlled explosion in the cylinder.
This so-called ultra lean burn mode sacrifices a bit of outright power, but greatly reduces the amount of fuel used during times when the vehicle requires very little grunt idling, coasting, decelerating, etc.
GDI engines also react more quickly to these changes in timing and amount of fuel addition, increasing driveability. Additionally, the vehicle is able to more quickly adjust based on inputs from sensors located downstream from the combustion chamber, keeping the dirty emissions blowing out of the tail pipe in check.
Some automakers have even experimented with using GDI to fire an additional burst of fuel into the cylinder to create secondary explosion during the combustion cycle, resulting in potentially even more power and efficiency.
Here's a fun fact: direct injection technology is not really as new as you may think. The technology has been around since the s for gasoline engines and is actually already in use in most diesel engines.
Are there any potential drawbacks to GDI? You may be asking, "If GDI is so great, why isn't it in every new car? Part of the reason is that manufacturing a direct-injected engine is more expensive due to component complexity, which means that the car the engine eventually powers would also be more expensive to buy. For example, the injectors on a GDI engine must be more rugged than port injectors in order to withstand the heat and pressure of hundreds or even thousands of tiny explosions per minute.
Additionally, because a GDI system needs to be able to inject fuel into a pressurized combustion chamber, the fuel lines supplying the gasoline need to be even higher in compression. GDI fuel systems can run at many thousand psi versus the 40 to 60 psi of port injection systems. The price of these components is dropping, but generally and for now port injection is cheaper and "good enough" for most economy cars. Additionally, some owners and maintainers of GDI engines particularly higher-performance, turbocharged models have reported that direct-injection systems see increased carbon buildup in backsides of their intake valves, resulting in reduced airflow and performance over time.
Password recovery. Google News. May 18, By Rohit Khurana. PFI engines use a three-way catalytic converter, exhaust sensors and computer-controlled engine management to constantly adjust the fuel-to-air ratio injected into each cylinder. With a GDi engine, fuel is injected directly into the combustion chamber, not the intake port.
The benefit of this system is that fuel is used more efficiently. Without the need to pump fuel into the intake port, mechanical and pumping losses are reduced significantly. In a GDi engine fuel is also injected at higher pressures so fuel droplet sizes are smaller. Injection pressures are in excess of bar compared to a PFI injection pressure of 3 to 5 bar.
The intake only supplies air to the combustion chamber with direct injection. GDI is the leading technology today and is only going to improve in the coming years. Port fuel injection still might have a place, but as a secondary player for low-speed conditions. Check The Part! Education: Selling Shocks And Struts. Magazine Current Issue Past Issues. Connect with us. Advertise Subscribe Contact Us. By Brendan Baker.
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